ALBERT

Beschreibung: Publication date: 19 July 2016 Source: Cell Reports, Volume 16, Issue 3 Author(s): Sandra Malmgren Hill, Xinxin Hao, Johan Grönvall, Stephanie Spikings-Nordby, Per O. Widlund, Triana Amen, Anna Jörhov, Rebecca Josefson, Daniel Kaganovich, Beidong Liu, Thomas Nyström Age can be reset during mitosis in both yeast and stem cells to generate a young daughter cell from an aged and deteriorated one. This phenomenon requires asymmetry-generating genes (AGGs) that govern the asymmetrical inheritance of aggregated proteins. Using a genome-wide imaging screen to identify AGGs in Saccharomyces cerevisiae , we discovered a previously unknown role for endocytosis, vacuole fusion, and the myosin-dependent adaptor protein Vac17 in asymmetrical inheritance of misfolded proteins. Overproduction of Vac17 increases deposition of aggregates into cytoprotective vacuole-associated sites, counteracts age-related breakdown of endocytosis and vacuole integrity, and extends replicative lifespan. The link between damage asymmetry and vesicle trafficking can be explained by a direct interaction between aggregates and vesicles. We also show that the protein disaggregase Hsp104 interacts physically with endocytic vesicle-associated proteins, such as the dynamin-like protein, Vps1, which was also shown to be required for Vac17-dependent sequestration of protein aggregates. These data demonstrate that two physiognomies of aging—reduced endocytosis and protein aggregation—are interconnected and regulated by Vac17. Graphical abstract Teaser Cellular rejuvenation is enabled by asymmetrical inheritance of damaged proteins. Using a genome-wide imaging screen to identify asymmetry-generating genes, Hill et al. demonstrate a role for vesicle trafficking, membrane fusion, and the myosin-dependent adaptor protein Vac17 in the asymmetric inheritance of misfolded proteins and consequently in the regulation of lifespan.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Mahesh S. Padanad, Georgia Konstantinidou, Niranjan Venkateswaran, Margherita Melegari, Smita Rindhe, Matthew Mitsche, Chendong Yang, Kimberly Batten, Kenneth E. Huffman, Jingwen Liu, Ximing Tang, Jaime Rodriguez-Canales, Neda Kalhor, Jerry W. Shay, John D. Minna, Jeffrey McDonald, Ignacio I. Wistuba, Ralph J. DeBerardinis, Pier Paolo Scaglioni KRAS is one of the most commonly mutated oncogenes in human cancer. Mutant KRAS aberrantly regulates metabolic networks. However, the contribution of cellular metabolism to mutant KRAS tumorigenesis is not completely understood. We report that mutant KRAS regulates intracellular fatty acid metabolism through Acyl-coenzyme A ( CoA ) synthetase long-chain family member 3 ( ACSL3 ), which converts fatty acids into fatty Acyl-CoA esters, the substrates for lipid synthesis and β - oxidation. ACSL3 suppression is associated with depletion of cellular ATP and causes the death of lung cancer cells. Furthermore, mutant KRAS promotes the cellular uptake, retention, accumulation, and β-oxidation of fatty acids in lung cancer cells in an ACSL3 -dependent manner. Finally, ACSL3 is essential for mutant KRAS lung cancer tumorigenesis in vivo and is highly expressed in human lung cancer. Our data demonstrate that mutant KRAS reprograms lipid homeostasis, establishing a metabolic requirement that could be exploited for therapeutic gain. Graphical abstract Teaser In Brief: Padanad et al. find that ACSL3 is the critical enzyme required for viability of mutant KRAS lung cancer cells in vitro and for lung cancer initiation and progression in vivo. ACSL3 mediates survival and tumorigenesis of mutant KRAS lung cancer cells by promoting uptake, retention, and β-oxidation of fatty acids.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Junghee Jin, Seung-Nam Kim, Xuqing Liu, Haijun Zhang, Chao Zhang, Ji-Seon Seo, Yong Kim, Tao Sun Emerging evidence has shown that noncoding RNAs, particularly microRNAs (miRNAs), contribute to the pathogenesis of mood and anxiety disorders, although the molecular mechanisms are poorly understood. Here, we show that altered levels of miR-17-92 in adult hippocampal neural progenitors have a significant impact on neurogenesis and anxiety- and depression-related behaviors in mice. miR-17-92 deletion in adult neural progenitors decreases neurogenesis in the dentate gyrus, while its overexpression increases neurogenesis. miR-17-92 affects neurogenesis by regulating genes in the glucocorticoid pathway, especially serum- and glucocorticoid-inducible protein kinase-1 (Sgk1). miR-17-92 knockout mice show anxiety- and depression-like behaviors, whereas miR-17-92 overexpressing mice exhibit anxiolytic and antidepression-like behaviors. Furthermore, we show that miR-17-92 expression in the adult mouse hippocampus responds to chronic stress, and miR-17-92 rescues proliferation defects induced by corticosterone in hippocampal neural progenitors. Our study uncovers a crucial role for miR-17-92 in adult neural progenitors through regulation of neurogenesis and anxiety- and depression-like behaviors. Graphical abstract Teaser The molecular pathogenesis of anxiety and depression disorders is poorly understood. Jin et al. show that microRNA miR-17-92 plays a critical role in regulating adult hippocampal neurogenesis and anxiety- and depression-like behaviors by modifying expression of genes in the glucocorticoid pathway.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Feng Jiang, Xia Wang, Bei Wang, Lihong Chen, Zhendong Zhao, Nicholas R. Waterfield, Guowei Yang, Qi Jin Pseudomonas aeruginosa is an opportunistic pathogen that regularly causes nosocomial infections in hospitalized patients. The type VI secretion system (T6SS) is responsible for the secretion of numerous virulence effector proteins that can both interfere with competing microbes and manipulate host cells. Here, we report a detailed investigation of a P. aeruginosa H2-T6SS-dependent phospholipase effector, TplE, which acts as a trans-kingdom toxin. Delivery of TplE to the periplasmic space of rival bacteria leads to growth inhibition. Importantly, TplE, also contains a eukaryotic PGAP1-like domain, which targets the host ER apparatus, ultimately leading to disruption of the ER. TplE activity leads to the activation of the unfolded protein response (UPR) through the IRE1α-XBP1 pathway, enhancing autophagic flux. These findings indicate that this T6SS-delivered phospholipase effector is active against both prokaryotic and eukaryotic cellular targets, highlighting the T6SS as a versatile weapon in the Pseudomonas arsenal. Graphical abstract Teaser Jiang et al. report that the P. aeruginosa T6SS PGAP1-like phospholipase effector (TplE) targets the periplasm of competing bacteria to inhibit their growth. TplE can also target and disrupt the ER of eukaryotic cells, leading to ER stress and autophagic flux in the host cells.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Seung-Hye Lee, Claire E. Le Pichon, Oskar Adolfsson, Valérie Gafner, Maria Pihlgren, Han Lin, Hilda Solanoy, Robert Brendza, Hai Ngu, Oded Foreman, Ruby Chan, James A. Ernst, Danielle DiCara, Isidro Hotzel, Karpagam Srinivasan, David V. Hansen, Jasvinder Atwal, Yanmei Lu, Daniela Bumbaca, Andrea Pfeifer, Ryan J. Watts, Andreas Muhs, Kimberly Scearce-Levie, Gai Ayalon The spread of tau pathology correlates with cognitive decline in Alzheimer’s disease. In vitro, tau antibodies can block cell-to-cell tau spreading. Although mechanisms of anti-tau function in vivo are unknown, effector function might promote microglia-mediated clearance. In this study, we investigated whether antibody effector function is required for targeting tau. We compared efficacy in vivo and in vitro of two versions of the same tau antibody, with and without effector function, measuring tau pathology, neuron health, and microglial function. Both antibodies reduced accumulation of tau pathology in Tau-P301L transgenic mice and protected cultured neurons against extracellular tau-induced toxicity. Only the full-effector antibody enhanced tau uptake in cultured microglia, which promoted release of proinflammatory cytokines. In neuron-microglia co-cultures, only effectorless anti-tau protected neurons, suggesting full-effector tau antibodies can induce indirect toxicity via microglia. We conclude that effector function is not required for efficacy, and effectorless tau antibodies may represent a safer approach to targeting tau. Graphical abstract Teaser Lee et al. report that antibody effector function is not required for targeting tau with antibodies in vivo and in cultured neurons. The authors propose that reducing anti-tau effector function may offer a safer approach for targeting tau by avoiding engagement of microglia that may induce inflammatory responses.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Rotem Ben-Tov Perry, Ida Rishal, Ella Doron-Mandel, Ashley L. Kalinski, Katalin F. Medzihradszky, Marco Terenzio, Stefanie Alber, Sandip Koley, Albina Lin, Meir Rozenbaum, Dmitry Yudin, Pabitra K. Sahoo, Cynthia Gomes, Vera Shinder, Wasim Geraisy, Eric A. Huebner, Clifford J. Woolf, Avraham Yaron, Alma L. Burlingame, Jeffery L. Twiss, Mike Fainzilber How can cells sense their own size to coordinate biosynthesis and metabolism with their growth needs? We recently proposed a motor-dependent bidirectional transport mechanism for axon length and cell size sensing, but the nature of the motor-transported size signals remained elusive. Here, we show that motor-dependent mRNA localization regulates neuronal growth and cycling cell size. We found that the RNA-binding protein nucleolin is associated with importin β1 mRNA in axons. Perturbation of nucleolin association with kinesins reduces its levels in axons, with a concomitant reduction in axonal importin β1 mRNA and protein levels. Strikingly, subcellular sequestration of nucleolin or importin β1 enhances axonal growth and causes a subcellular shift in protein synthesis. Similar findings were obtained in fibroblasts. Thus, subcellular mRNA localization regulates size and growth in both neurons and cycling cells. Graphical abstract Teaser Perry et al. show that motor-dependent mRNA localization regulates neuronal growth and cycling cell size. They implicate the RNA-binding protein nucleolin in importin β1 mRNA transport to neuronal axons and to the cellular periphery in fibroblasts. Perturbation of this mechanism affects growth and shifts protein synthesis, regulating axon length and cell size.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Anna Prudova, Vasilena Gocheva, Ulrich auf dem Keller, Ulrich Eckhard, Oakley C. Olson, Leila Akkari, Georgina S. Butler, Nikolaus Fortelny, Philipp F. Lange, Jennifer C. Mark, Johanna A. Joyce, Christopher M. Overall Deregulated cathepsin proteolysis occurs across numerous cancers, but in vivo substrates mediating tumorigenesis remain ill-defined. Applying 8-plex iTRAQ terminal amine isotopic labeling of substrates (TAILS), a systems-level N-terminome degradomics approach, we identified cathepsin B, H, L, S, and Z in vivo substrates and cleavage sites with the use of six different cathepsin knockout genotypes in the Rip1-Tag2 mouse model of pancreatic neuroendocrine tumorigenesis. Among 1,935 proteins and 1,114 N termini identified by TAILS, stable proteolytic products were identified in wild-type tumors compared with one or more different cathepsin knockouts (17%–44% of 139 cleavages). This suggests a lack of compensation at the substrate level by other cathepsins. The majority of neo-N termini (56%–83%) for all cathepsins was consistent with protein degradation. We validated substrates, including the glycolytic enzyme pyruvate kinase M2 associated with the Warburg effect, the ER chaperone GRP78, and the oncoprotein prothymosin-alpha. Thus, the identification of cathepsin substrates in tumorigenesis improves the understanding of cathepsin functions in normal physiology and cancer. Graphical abstract Teaser Cathepsin proteases play a significant role in carcinogenesis, yet their in vivo substrates remain ill-defined. By using systems-level 8-plex TAILS proteomics, Prudova et al. demonstrate that, in the Rip1-Tag2 model of pancreatic cancer, degradation roles for cathepsins predominate, yet many proteins, mostly extracellular ones, are processed to produce stable cleavage products.

Beschreibung: Publication date: Available online 29 July 2016 Source: Cell Reports Author(s): Kimberly A. Dowd, Christina R. DeMaso, Rebecca S. Pelc, Scott D. Speer, Alexander R.Y. Smith, Leslie Goo, Derek J. Platt, John R. Mascola, Barney S. Graham, Mark J. Mulligan, Michael S. Diamond, Julie E. Ledgerwood, Theodore C. Pierson Recent epidemics of Zika virus (ZIKV) have been associated with congenital malformation during pregnancy and Guillain-Barré syndrome. There are two ZIKV lineages (African and Asian) that share >95% amino acid identity. Little is known regarding the ability of neutralizing antibodies elicited against one lineage to protect against the other. We investigated the breadth of the neutralizing antibody response following ZIKV infection by measuring the sensitivity of six ZIKV strains to neutralization by ZIKV-confirmed convalescent human serum or plasma samples. Contemporary Asian and early African ZIKV strains were similarly sensitive to neutralization regardless of the cellular source of virus. Furthermore, mouse immune serum generated after infection with African or Asian ZIKV strains was capable of neutralizing homologous and heterologous ZIKV strains equivalently. Because our study only defines a single ZIKV serotype, vaccine candidates eliciting robust neutralizing antibody responses should inhibit infection of both ZIKV lineages, including strains circulating in the Americas. Graphical abstract Teaser Dowd et al. investigate the breadth of the neutralizing antibody response to ZIKV. They demonstrate that contemporary South American, Asian, and early African ZIKV strains are similarly sensitive to neutralization by ZIKV-confirmed convalescent human serum.

Beschreibung: Publication date: 2 August 2016 Source: Cell Reports, Volume 16, Issue 5 Author(s): Megan Chastain, Qing Zhou, Olga Shiva, Leanne Whitmore, Pingping Jia, Xueyu Dai, Chenhui Huang, Maria Fadri-Moskwik, Ping Ye, Weihang Chai The telomeric CTC1/STN1/TEN1 (CST) complex has been implicated in promoting replication recovery under replication stress at genomic regions, yet its precise role is unclear. Here, we report that STN1 is enriched at GC-rich repetitive sequences genome-wide in response to hydroxyurea (HU)-induced replication stress. STN1 deficiency exacerbates the fragility of these sequences under replication stress, resulting in chromosome fragmentation. We find that upon fork stalling, CST proteins form distinct nuclear foci that colocalize with RAD51. Furthermore, replication stress induces physical association of CST with RAD51 in an ATR-dependent manner. Strikingly, CST deficiency diminishes HU-induced RAD51 foci formation and reduces RAD51 recruitment to telomeres and non-telomeric GC-rich fragile sequences. Collectively, our findings establish that CST promotes RAD51 recruitment to GC-rich repetitive sequences in response to replication stress to facilitate replication restart, thereby providing insights into the mechanism underlying genome stability maintenance. Graphical abstract Teaser Chastain et al. find that under replication stress, the telomeric complex CST interacts with RAD51 and is enriched at GC-rich repetitive fragile sites. CST suppression inhibits RAD51 recruitment to fragile sites, resulting in genome instability.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Niloufar Monhasery, Jens Moll, Carly Cuman, Manuel Franke, Larissa Lamertz, Rebecca Nitz, Boris Görg, Dieter Häussinger, Juliane Lokau, Doreen M. Floss, Roland Piekorz, Eva Dimitriadis, Christoph Garbers, Jürgen Scheller Interleukin (IL)-11 signaling is involved in various processes, including epithelial intestinal cell regeneration and embryo implantation. IL-11 signaling is initiated upon binding of IL-11 to IL-11R1 or IL-11R2, two IL-11α-receptor splice variants, and gp130. Here, we show that IL-11 signaling via IL-11R1/2:gp130 complexes occurs on both the apical and basolateral sides of polarized cells, whereas IL-6 signaling via IL-6R:gp130 complexes is restricted to the basolateral side. We show that basolaterally supplied IL-11 is transported and released to the apical extracellular space via transcytosis in an IL-11R1-dependent manner. By contrast, IL-6R and IL-11R2 do not promote transcytosis. In addition, we show that transcytosis of IL-11 is dependent on the intracellular domain of IL-11R1 and that synthetic transfer of the intracellular domain of IL-11R1 to IL-6R promotes transcytosis of IL-6. Our data define IL-11R as a cytokine receptor with transcytotic activity by which IL-11 and IL-6:soluble IL-6R complexes are transported across cellular barriers. Graphical abstract Teaser Monhasery et al. show that interleukin 11 (IL-11) signaling via IL-11 receptor:gp130 complexes occurs on both the apical and basolateral sides of polarized cells. The transcytotic activity of the IL-11 receptor allows IL-11 and interleukin-6:soluble interleukin-6 receptor complexes to be transported across cellular barriers.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Christian Laut Ebbesen, Eric Torsten Reifenstein, Qiusong Tang, Andrea Burgalossi, Saikat Ray, Susanne Schreiber, Richard Kempter, Michael Brecht The medial entorhinal cortex (MEC) and the adjacent parasubiculum are known for their elaborate spatial discharges (grid cells, border cells, etc.) and the precessing of spikes relative to the local field potential. We know little, however, about how spatio-temporal firing patterns map onto cell types. We find that cell type is a major determinant of spatio-temporal discharge properties. Parasubicular neurons and MEC layer 2 (L2) pyramids have shorter spikes, discharge spikes in bursts, and are theta-modulated (rhythmic, locking, skipping), but spikes phase-precess only weakly. MEC L2 stellates and layer 3 (L3) neurons have longer spikes, do not discharge in bursts, and are weakly theta-modulated (non-rhythmic, weakly locking, rarely skipping), but spikes steeply phase-precess. The similarities between MEC L3 neurons and MEC L2 stellates on one hand and parasubicular neurons and MEC L2 pyramids on the other hand suggest two distinct streams of temporal coding in the parahippocampal cortex. Graphical abstract Teaser Neurons in the parahippocampal cortex discharge in elaborate spatiotemporal firing patterns. Ebbesen et al. use juxtacellular recordings to show that the neuronal cell type is a major determinant of temporal discharge patterns such as bursting and phase precession.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Jeannine Gerhardt, Angela D. Bhalla, Jill Sergesketter Butler, James W. Puckett, Peter B. Dervan, Zev Rosenwaks, Marek Napierala Friedreich’s ataxia (FRDA) is caused by the expansion of GAA repeats located in the Frataxin (FXN) gene. The GAA repeats continue to expand in FRDA patients, aggravating symptoms and contributing to disease progression. The mechanism leading to repeat expansion and decreased FXN transcription remains unclear. Using single-molecule analysis of replicated DNA, we detected that expanded GAA repeats present a substantial obstacle for the replication machinery at the FXN locus in FRDA cells. Furthermore, aberrant origin activation and lack of a proper stress response to rescue the stalled forks in FRDA cells cause an increase in 3′-5′ progressing forks, which could enhance repeat expansion and hinder FXN transcription by head-on collision with RNA polymerases. Treatment of FRDA cells with GAA-specific polyamides rescues DNA replication fork stalling and alleviates expansion of the GAA repeats, implicating DNA triplexes as a replication impediment and suggesting that fork stalling might be a therapeutic target for FRDA. Graphical abstract Teaser Gerhardt et al. demonstrate that stable secondary structures, formed at the expanded GAA repeats in Friedreich’s ataxia patient cells, stall DNA replication. In addition, using a single DNA molecule approach to visualize the Frataxin locus, they show that aberrant activation of origins downstream of the GAA repeats alters replication fork direction.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Jacint G. Sanchez, Jessica J. Chiang, Konstantin M.J. Sparrer, Steven L. Alam, Michael Chi, Marcin D. Roganowicz, Banumathi Sankaran, Michaela U. Gack, Owen Pornillos Antiviral response pathways induce interferon by higher-order assembly of signaling complexes called signalosomes. Assembly of the RIG-I signalosome is regulated by K63-linked polyubiquitin chains, which are synthesized by the E3 ubiquitin ligase, TRIM25. We have previously shown that the TRIM25 coiled-coil domain is a stable, antiparallel dimer that positions two catalytic RING domains on opposite ends of an elongated rod. We now show that the RING domain is a separate self-association motif that engages ubiquitin-conjugated E2 enzymes as a dimer. RING dimerization is required for catalysis, TRIM25-mediated RIG-I ubiquitination, interferon induction, and antiviral activity. We also provide evidence that RING dimerization and E3 ligase activity are promoted by binding of the TRIM25 SPRY domain to the RIG-I effector domain. These results indicate that TRIM25 actively participates in higher-order assembly of the RIG-I signalosome and helps to fine-tune the efficiency of the RIG-I-mediated antiviral response. Graphical abstract Teaser Sanchez et al. elucidate the structural requirements for TRIM25 catalytic activation and its effector functions in the antiviral RIG-I pathway. Higher-order oligomerization of TRIM25 is promoted by RIG-I and likely constitutes a regulatory mechanism of cellular antiviral response.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Thomas Liebmann, Nicolas Renier, Karima Bettayeb, Paul Greengard, Marc Tessier-Lavigne, Marc Flajolet Amyloidosis is a major problem in over one hundred diseases, including Alzheimer’s disease (AD). Using the iDISCO visualization method involving targeted molecular labeling, tissue clearing, and light-sheet microscopy, we studied plaque formation in the intact AD mouse brain at up to 27 months of age. We visualized amyloid plaques in 3D together with tau, microglia, and vasculature. Volume imaging coupled to automated detection and mapping enables precise and fast quantification of plaques within the entire intact mouse brain. The present methodology is also applicable to analysis of frozen human brain samples without specialized preservation. Remarkably, amyloid plaques in human brain tissues showed greater 3D complexity and surprisingly large three-dimensional amyloid patterns, or TAPs. The ability to visualize amyloid in 3D, especially in the context of their micro-environment, and the discovery of large TAPs may have important scientific and medical implications. Graphical abstract Teaser Liebmann et al. present 3D renderings of Alzheimer’s disease in an entire mouse brain hemisphere using iDISCO. Volume imaging coupled to automated detection and mapping to the Allen Brain Atlas enables precise and fast quantification of plaques. Plaques in archival human brain samples showed a greater 3D complexity.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Laura Jacox, Justin Chen, Alyssa Rothman, Hillary Lathrop-Marshall, Hazel Sive The mouth arises from the extreme anterior domain (EAD), a region where the ectoderm and endoderm are directly juxtaposed. Here, we identify a “pre-mouth array” in Xenopus that forms soon after the cranial neural crest has migrated to lie on either side of the EAD. Initially, EAD ectoderm comprises a wide and short epithelial mass that becomes narrow and tall with cells and nuclei changing shape, a characteristic of convergent extension. The resulting two rows of cells—the pre-mouth array—later split down the midline to surround the mouth opening. Neural crest is essential for convergent extension and likely signals to the EAD through the Wnt/planar cell polarity (PCP) pathway. Fzl7 receptor is locally required in EAD ectoderm, while Wnt11 ligand is required more globally. Indeed, heterologous cells expressing Wnt11 can elicit EAD convergent extension. The study reveals a precise cellular mechanism that positions and contributes to the future mouth. Graphical abstract Teaser Jacox et al. identify a precise cellular organization of extreme anterior domain (EAD) ectoderm—the “pre-mouth array”—that contributes to the future mouth opening in Xenopus . Their data indicate that the pre-mouth array forms by convergent extension, under control of adjacent neural crest and Wnt/PCP signaling.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Jing-kuan Wei, Wen-chao Wang, Rong-wei Zhai, Yu-hua Zhang, Shang-chuan Yang, Joshua Rizak, Ling Li, Li-qi Xu, Li Liu, Ming-ke Pan, Ying-zhou Hu, Abdelaziz Ghanemi, Jing Wu, Li-chuan Yang, Hao Li, Long-bao Lv, Jia-li Li, Yong-gang Yao, Lin Xu, Xiao-li Feng, Yong Yin, Dong-dong Qin, Xin-tian Hu, Zheng-bo Wang Here, we examine whether neurons differentiated from transplanted stem cells can integrate into the host neural network and function in awake animals, a goal of transplanted stem cell therapy in the brain. We have developed a technique in which a small “hole” is created in the inferior colliculus (IC) of rhesus monkeys, then stem cells are transplanted in situ to allow for investigation of their integration into the auditory neural network. We found that some transplanted cells differentiated into mature neurons and formed synaptic input/output connections with the host neurons. In addition, c-Fos expression increased significantly in the cells after acoustic stimulation, and multichannel recordings indicated IC specific tuning activities in response to auditory stimulation. These results suggest that the transplanted cells have the potential to functionally integrate into the host neural network. Graphical abstract Teaser Integration of differentiated neurons into a functioning neural network is important for the development of stem cell therapies. Wang et al. found that neurons differentiated from transplanted stem cells respond to auditory stimuli in awake monkeys after transplantation.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Nicolas Huguenin-Dezot, Virginia De Cesare, Julien Peltier, Axel Knebel, Yosua Adi Kristaryianto, Daniel T. Rogerson, Yogesh Kulathu, Matthias Trost, Jason W. Chin Ubiquitin is post-translationally modified by phosphorylation at several sites, but the consequences of these modifications are largely unknown. Here, we synthesize multi-milligram quantities of ubiquitin phosphorylated at serine 20, serine 57, and serine 65 via genetic code expansion. We use these phosphoubiquitins for the enzymatic assembly of 20 isomeric phosphoubiquitin dimers, with different sites of isopeptide linkage and/or phosphorylation. We discover that phosphorylation of serine 20 on ubiquitin converts UBE3C from a dual-specificity E3 ligase into a ligase that primarily synthesizes K48 chains. We profile the activity of 31 deubiquitinases on the isomeric phosphoubiquitin dimers in 837 reactions, and we discover that phosphorylation at distinct sites in ubiquitin can activate or repress cleavage of a particular linkage by deubiquitinases and that phosphorylation at a single site in ubiquitin can control the specificity of deubiquitinases for distinct ubiquitin linkages. Graphical abstract Teaser Huguenin-Dezot et al. combine genetic code expansion and enzymatic assembly to synthesize 20 isomeric phosphoubiquitin chains with distinct Ser phosphorylation and/or isopeptide linkage sites. They discover that ubiquitin phosphorylation can control E3 ligase specificity and deubiquitinase specificity.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Minhee Kim, Brian P. O’Rourke, Rajesh Kumar Soni, Prasad V. Jallepalli, Ronald C. Hendrickson, Meng-Fu Bryan Tsou PLK4 is the major kinase driving centriole duplication. Duplication occurs only once per cell cycle, forming one new (or daughter) centriole that is tightly engaged to the preexisting (or mother) centriole. Centriole engagement is known to block the reduplication of mother centrioles, but the molecular identity responsible for the block remains unclear. Here, we show that the centriolar cartwheel, the geometric scaffold for centriole assembly, forms the identity of daughter centrioles essential for the block, ceasing further duplication of the mother centriole to which it is engaged. To ensure a steady block, we found that the cartwheel requires constant maintenance by PLK4 through phosphorylation of the same substrate that drives centriole assembly, revealing a parsimonious control in which “assembly” and “block for new assembly” are linked through the same catalytic reaction to achieve homeostasis. Our results support a recently deduced model that the cartwheel-bound PLK4 directly suppresses centriole reduplication. Graphical abstract Teaser Cellular structures are maintained at constant numbers by balancing the “promotion” and “suppression” of their biogenesis, two processes opposing each other. Through studies on the cell-division organelle, centrioles, Kim et al. found that the two opposing processes are intimately coupled to the same catalytic reaction involving the kinase PLK4, thereby safeguarding centriole homeostasis.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Shengjie Xue, Chang Liu, Xiujie Sun, Weiyun Li, Chi Zhang, Xin Zhou, Yao Lu, Jun Xiao, Chunyang Li, Xiaoyan Xu, Bing Sun, Guoliang Xu, Hongyan Wang Type I interferons (IFNs) play both beneficial and harmful roles in antiviral responses. Precise regulation of host type I IFNs is thus needed to prevent immune dysregulation. Here, we find that the DNA demethylase TET3 is a negative regulator of IFN-β in response to poly(I:C) stimulation or viral infection. Deletion of TET3 enhances antiviral responses, with elevated expression of IFN-β and IFN-stimulated genes. The catalytic domain of TET3 was critical for the suppression of IFN-β production, but TET3 enzymatic activity was dispensable. Instead, the catalytic domain of TET3 interacts with HDAC1 and SIN3A, thus enhancing their binding to the Ifnb1 promoter. Our study demonstrates that TET3 negatively regulates type I IFN production independent of DNA demethylation. This not only sheds light on TET3 as a signaling protein in immune cells for gene regulation but also will help to develop strategies to prevent type I IFN-related disease. Graphical abstract Teaser Xue et al. find that TET3 expression is decreased after viral infection and that TET3 reduction enhances type I IFN production and virus clearance. Mechanistically, TET3 recruits HDAC1 to the Ifnb1 promoter, thus suppressing type I IFN transcription.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Chieh Hsu, Vincent Jaquet, Mumun Gencoglu, Attila Becskei Bistability plays an important role in cellular memory and cell-fate determination. A positive feedback loop can generate bistability if it contains ultrasensitive molecular reactions. It is often difficult to detect bistability based on such molecular mechanisms due to its intricate interaction with cellular growth. We constructed transcriptional feedback loops in yeast. To eliminate growth alterations, we reduced the protein levels of the transcription factors by tuning the translation rates over two orders of magnitude with designed RNA stem loops. We modulated two ultrasensitive reactions, homodimerization and the cooperative binding of the transcription factor to the promoter. Either of them is sufficient to generate bistability on its own, and when acting together, a particularly robust bistability emerges. This bistability persists even in the presence of a negative feedback loop. Given that protein homodimerization is ubiquitous, it is likely to play a major role in the behavior of regulatory networks. Graphical abstract Teaser Using RNA stem loops to attenuate translation rates, Hsu et al. designed synthetic feedback loops in yeast to study the sources of bistability. They show that cooperative binding of a transcription factor to its promoter or its dimerization generates bistability. Bistability is particularly robust when the dimerizing transcription factor binds to the promoter cooperatively.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Brian J. McMillan, Christine Tibbe, Hyesung Jeon, Andrew A. Drabek, Thomas Klein, Stephen C. Blacklow The endosomal sorting complex required for transport (ESCRT) is a conserved protein complex that facilitates budding and fission of membranes. It executes a key step in many cellular events, including cytokinesis and multi-vesicular body formation. The ESCRT-III protein Shrub in flies, or its homologs in yeast (Snf7) or humans (CHMP4B), is a critical polymerizing component of ESCRT-III needed to effect membrane fission. We report the structural basis for polymerization of Shrub and define a minimal region required for filament formation. The X-ray structure of the Shrub core shows that individual monomers in the lattice interact in a staggered arrangement using complementary electrostatic surfaces. Mutations that disrupt interface salt bridges interfere with Shrub polymerization and function. Despite substantial sequence divergence and differences in packing interactions, the arrangement of Shrub subunits in the polymer resembles that of Snf7 and other family homologs, suggesting that this intermolecular packing mechanism is shared among ESCRT-III proteins. Graphical abstract Teaser The ESCRT complex facilitates budding and fission of cellular membranes. McMillan et al. report the X-ray structure of the fly ESCRT-III component Shrub. The packing of subunits in the structure, mirrored in the distant yeast homolog Snf7, suggests a general model for the subunit polymerization step required for membrane fission.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Emilie-Fleur Gautier, Sarah Ducamp, Marjorie Leduc, Virginie Salnot, François Guillonneau, Michael Dussiot, John Hale, Marie-Catherine Giarratana, Anna Raimbault, Luc Douay, Catherine Lacombe, Narla Mohandas, Frédérique Verdier, Yael Zermati, Patrick Mayeux Mass spectrometry-based proteomics now enables the absolute quantification of thousands of proteins in individual cell types. We used this technology to analyze the dynamic proteome changes occurring during human erythropoiesis. We quantified the absolute expression of 6,130 proteins during erythroid differentiation from late burst-forming units-erythroid (BFU-Es) to orthochromatic erythroblasts. A modest correlation between mRNA and protein expression was observed. We identified several proteins with unexpected expression patterns in erythroid cells, highlighting a breakpoint in the erythroid differentiation process at the basophilic stage. We also quantified the distribution of proteins between reticulocytes and pyrenocytes after enucleation. These analyses identified proteins that are actively sorted either with the reticulocyte or the pyrenocyte. Our study provides the absolute quantification of protein expression during a complex cellular differentiation process in humans, and it establishes a framework for future studies of disordered erythropoiesis. Graphical abstract Teaser Gautier et al. use quantitative mass spectrometry to determine the absolute proteome composition of human erythroid progenitors throughout the differentiation process and the quantitative distribution of proteins between reticulocytes and pyrenocytes after enucleation.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Laura Grasso, Olga Suska, Lindsay Davidson, Thomas Gonatopoulos-Pournatzis, Ritchie Williamson, Lize Wasmus, Simone Wiedlich, Mark Peggie, Marios P. Stavridis, Victoria H. Cowling The mRNA cap recruits factors essential for transcript processing and translation initiation. We report that regulated mRNA cap methylation is a feature of embryonic stem cell (ESC) differentiation. Expression of the mRNA cap methyltransferase activating subunit RAM is elevated in ESCs, resulting in high levels of mRNA cap methylation and expression of a cohort of pluripotency-associated genes. During neural differentiation, RAM is suppressed, resulting in repression of pluripotency-associated factors and expression of a cohort of neural-associated genes. An established requirement of differentiation is increased ERK1/2 activity, which suppresses pluripotency-associated genes. During differentiation, ERK1/2 phosphorylates RAM serine-36, targeting it for ubiquitination and proteasomal degradation, ultimately resulting in changes in gene expression associated with loss of pluripotency. Elevated RAM expression also increases the efficiency of fibroblast reprogramming. Thus, the mRNA cap emerges as a dynamic mark that instructs change in gene expression profiles during differentiation and reprogramming. Graphical abstract Teaser The mRNA cap stabilizes transcripts and recruits processing and translation factors. Grasso et al. report that the mRNA cap methyltransferase RNMT-RAM is highly expressed in embryonic stem cells and is important for pluripotency-associated gene expression. Repression of RAM occurs during neural differentiation and is important for expression of neural-associated genes.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): David W. Hawman, Julie M. Fox, Alison W. Ashbrook, Nicholas A. May, Kristin M.S. Schroeder, Raul M. Torres, James E. Crowe, Terence S. Dermody, Michael S. Diamond, Thomas E. Morrison Chikungunya virus (CHIKV) and related alphaviruses cause epidemics of acute and chronic musculoskeletal disease. To investigate the mechanisms underlying the failure of immune clearance of CHIKV, we studied mice infected with an attenuated CHIKV strain (181/25) and the pathogenic parental strain (AF15561), which differ by five amino acids. Whereas AF15561 infection of wild-type mice results in viral persistence in joint tissues, 181/25 is cleared. In contrast, 181/25 infection of μMT mice lacking mature B cells results in viral persistence in joint tissues, suggesting that virus-specific antibody is required for clearance of infection. Mapping studies demonstrated that a highly conserved glycine at position 82 in the A domain of the E2 glycoprotein impedes clearance and neutralization of multiple CHIKV strains. Remarkably, murine and human antibodies targeting E2 domain B failed to neutralize pathogenic CHIKV strains efficiently. Our data suggest that pathogenic CHIKV strains evade E2 domain-B-neutralizing antibodies to establish persistence. Graphical abstract Teaser Hawman et al. have found that a highly conserved glycine at E2-82 promotes CHIKV persistence in joints and impairs neutralization by antibodies targeting E2 domain B. Mutation of E2-82 to arginine allows viral clearance and enhances neutralization, providing a structural basis for how chronic CHIKV joint infection evades B-cell-mediated clearance.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Clémentine Bosch-Bouju, Thomas Larrieu, Louisa Linders, Olivier J. Manzoni, Sophie Layé Chronic social defeat stress (CSDS) is a clinically relevant model of mood disorders. The relationship between the CSDS model and a physiologically pertinent paradigm of synaptic plasticity is not known. Here, we found that cluster analysis of the emotional behavior states of mice exposed to CSDS allowed their segregation into anxious and non-anxious groups. Endocannabinoid-mediated spike-timing dependent plasticity (STDP) in the nucleus accumbens was attenuated in non-anxious mice and abolished in anxious mice. Anxiety-like behavior in stressed animals was specifically correlated with their ability to produce STDP. Pharmacological enhancement of 2-arachidonoyl glycerol (2-AG) signaling in the nucleus accumbens normalized the anxious phenotype and STDP in anxious mice. These data reveal that endocannabinoid modulation of synaptic efficacy in response to a naturalistic activity pattern is both a molecular correlate of behavioral adaptability and a crucial factor in the adaptive response to chronic stress. Graphical abstract Teaser Bosch-Bouju et al. used cluster analysis to segregate mice into anxious and non-anxious populations following social defeat. Endocannabinoid spike-timing-dependent plasticity is abolished in anxious mice only. Enhancement of endocannabinoid signaling in the nucleus accumbens restores anxiety-like behaviors and synaptic plasticity. Endocannabinoid plasticity is thus a synaptic marker of anxiety following social defeat.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Devon M. Chenette, Adam B. Cadwallader, Tiffany L. Antwine, Lauren C. Larkin, Jinhua Wang, Bradley B. Olwin, Robert J. Schneider Following skeletal muscle injury, muscle stem cells (satellite cells) are activated, proliferate, and differentiate to form myofibers. We show that mRNA-decay protein AUF1 regulates satellite cell function through targeted degradation of specific mRNAs containing 3′ AU-rich elements (AREs). auf1 −/− mice undergo accelerated skeletal muscle wasting with age and impaired skeletal muscle repair following injury. Satellite cell mRNA analysis and regeneration studies demonstrate that auf1 −/− satellite cell self-renewal is impaired due to increased stability and overexpression of ARE-mRNAs, including cell-autonomous overexpression of matrix metalloprotease MMP9. Secreted MMP9 degrades the skeletal muscle matrix, preventing satellite-cell-mediated regeneration and return to quiescence. Blocking MMP9 activity in auf1 −/− mice restores skeletal muscle repair and maintenance of the satellite cell population. Control of ARE-mRNA decay by AUF1 represents a mechanism for adult stem cell regulation and is implicated in human skeletal muscle wasting diseases. Graphical abstract Teaser Chenette et al. demonstrate that the mRNA binding protein AUF1 regulates muscle stem (satellite) cell function and fate through targeted degradation of mRNAs that determine satellite cell fate. auf1 −/− mice undergo accelerated skeletal muscle wasting with aging and impaired muscle repair following injury, and AUF1 mutations are implicated in some forms of muscular dystrophy.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Yuki Sugaya, Maya Yamazaki, Motokazu Uchigashima, Kenta Kobayashi, Masahiko Watanabe, Kenji Sakimura, Masanobu Kano Endocannabinoid signaling is considered to suppress excessive excitability of neural circuits and to protect the brain from seizures. However, the precise mechanisms of this effect are poorly understood. Here, we report that 2-arachidonoylglycerol (2-AG), one of the two major endocannabinoids, is crucial for suppressing seizures. We found that kainate-induced seizures in mice lacking the 2-AG synthesizing enzyme, diacylglycerol lipase α, were much more severe compared with those in cannabinoid CB 1 receptor knockout mice and were comparable to those in mice lacking both CB 1 - and CB 2 -receptor-mediated signaling. In the dentate gyrus, 2-AG suppressed excitatory input around the inner and middle molecular layers through CB 1 and presumably CB 2 receptors, respectively. This 2-AG-mediated suppression contributed to decreased granule cell excitability and the dampening of seizures. Furthermore, lack of 2-AG signaling enhanced kindling epileptogenesis and spontaneous seizures after kainate-induced status epilepticus. These results highlight critical roles of 2-AG signaling in the suppression of epileptic seizures. Graphical abstract Teaser Endocannabinoid signaling suppresses epileptic seizures, but the precise mechanism of this action is undetermined. Sugaya et al. demonstrate that the endocannabinoid 2-arachidonoylglycerol can suppress seizures and epileptogenesis by reducing excitatory synaptic inputs in the dentate gyrus through CB 1 and presumably CB 2 cannabinoid receptors.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Christian M. Simon, Anna M. Janas, Francesco Lotti, Juan Carlos Tapia, Livio Pellizzoni, George Z. Mentis In spinal muscular atrophy, a neurodegenerative disease caused by ubiquitous deficiency in the survival motor neuron (SMN) protein, sensory-motor synaptic dysfunction and increased excitability precede motor neuron (MN) loss. Whether central synaptic dysfunction and MN hyperexcitability are cell-autonomous events or they contribute to MN death is unknown. We addressed these issues using a stem-cell-based model of the motor circuit consisting of MNs and both excitatory and inhibitory interneurons (INs) in which SMN protein levels are selectively depleted. We show that SMN deficiency induces selective MN death through cell-autonomous mechanisms, while hyperexcitability is a non-cell-autonomous response of MNs to defects in pre-motor INs, leading to loss of glutamatergic synapses and reduced excitation. Findings from our in vitro model suggest that dysfunction and loss of MNs result from differential effects of SMN deficiency in distinct neurons of the motor circuit and that hyperexcitability does not trigger MN death. Graphical abstract Teaser Ubiquitous SMN deficiency causes motor circuit dysfunction and increased excitability and death of MNs in spinal muscular atrophy. Simon et al. used a stem cell model of the motor circuit to show that MN degeneration is cell autonomous, while MN hyperexcitability is a non-autonomous homeostatic response to pre-synaptic dysfunction of excitatory interneurons.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Alison M. Kurimchak, Claude Shelton, Kelly E. Duncan, Katherine J. Johnson, Jennifer Brown, Shane O’Brien, Rashid Gabbasov, Lauren S. Fink, Yuesheng Li, Nicole Lounsbury, Magid Abou-Gharbia, Wayne E. Childers, Denise C. Connolly, Jonathan Chernoff, Jeffrey R. Peterson, James S. Duncan Small-molecule BET bromodomain inhibitors (BETis) are actively being pursued in clinical trials for the treatment of a variety of cancers, but the mechanisms of resistance to BETis remain poorly understood. Using a mass spectrometry approach that globally measures kinase signaling at the proteomic level, we evaluated the response of the kinome to targeted BETi treatment in a panel of BRD4-dependent ovarian carcinoma (OC) cell lines. Despite initial inhibitory effects of BETi, OC cells acquired resistance following sustained treatment with the BETi JQ1. Through application of multiplexed inhibitor beads (MIBs) and mass spectrometry, we demonstrate that BETi resistance is mediated by adaptive kinome reprogramming, where activation of compensatory pro-survival kinase networks overcomes BET protein inhibition. Furthermore, drug combinations blocking these kinases may prevent or delay the development of drug resistance and enhance the efficacy of BETi therapy. Graphical abstract Teaser BET inhibitors are currently being evaluated in clinical trials for a number of cancers, including ovarian cancer. Kurimchak et al. demonstrate that BET inhibitors may have limited success as single agents in ovarian cancer due to adaptive kinome reprogramming and will require combination therapies targeting kinases and BET bromodomain proteins

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Anna Schurich, Laura J. Pallett, Danyal Jajbhay, Jessica Wijngaarden, Itziar Otano, Upkar S. Gill, Navjyot Hansi, Patrick T. Kennedy, Eleni Nastouli, Richard Gilson, Christian Frezza, Sian M. Henson, Mala K. Maini T cells undergo profound metabolic changes to meet the increased energy demands of maintaining an antiviral response. We postulated that differences in metabolic reprogramming would shape the efficacy of CD8 T cells mounted against persistent viral infections. We found that the poorly functional PD-1 hi T cell response against hepatitis B virus (HBV) had upregulated the glucose transporter, Glut1, an effect recapitulated by oxygen deprivation to mimic the intrahepatic environment. Glut1 hi HBV-specific T cells were dependent on glucose supplies, unlike the more functional cytomegalovirus (CMV)-specific T cells that could utilize oxidative phosphorylation in the absence of glucose. The inability of HBV-specific T cells to switch to oxidative phosphorylation was accompanied by increased mitochondrial size and lower mitochondrial potential, indicative of mitochondrial dysfunction. Interleukin (IL)-12, which recovers HBV-specific T cell effector function, increased their mitochondrial potential and reduced their dependence on glycolysis. Our findings suggest that mitochondrial defects limit the metabolic plasticity of exhausted HBV-specific T cells. Graphical abstract Teaser T cells undergo extensive metabolic changes upon activation. Schurich et al. find that functional and exhausted human-virus-specific CD8 T cells have distinct metabolic phenotypes, shaping their effector capacity.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Yalin Liao, Alfredo Castello, Bernd Fischer, Stefan Leicht, Sophia Föehr, Christian K. Frese, Chikako Ragan, Sebastian Kurscheid, Eloisa Pagler, Hao Yang, Jeroen Krijgsveld, Matthias W. Hentze, Thomas Preiss RNA functions through the dynamic formation of complexes with RNA-binding proteins (RBPs) in all clades of life. We determined the RBP repertoire of beating cardiomyocytic HL-1 cells by jointly employing two in vivo proteomic methods, mRNA interactome capture and RBDmap. Together, these yielded 1,148 RBPs, 391 of which are shared with all other available mammalian RBP repertoires, while 393 are thus far unique to cardiomyocytes. RBDmap further identified 568 regions of RNA contact within 368 RBPs. The cardiomyocyte mRNA interactome composition reflects their unique biology. Proteins with roles in cardiovascular physiology or disease, mitochondrial function, and intermediary metabolism are all highly represented. Notably, we identified 73 metabolic enzymes as RBPs. RNA-enzyme contacts frequently involve Rossmann fold domains with examples in evidence of both, mutual exclusivity of, or compatibility between RNA binding and enzymatic function. Our findings raise the prospect of previously hidden RNA-mediated regulatory interactions among cardiomyocyte gene expression, physiology, and metabolism. Graphical abstract Teaser RNA functions through dynamic interactions with RNA-binding proteins (RBPs) in all clades of life. In this article, Liao et al. present the RBP repertoire of murine cardiomyocytes. Their findings reflect the unique cardiomyocyte biology and raise the prospect of previously hidden RNA-mediated regulatory interactions between gene expression, physiology, and metabolism.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Chih-Wei Chen, Ning Tsao, Lin-Yi Huang, Yun Yen, Xiyong Liu, Christine Lehman, Yuh-Hwa Wang, Mei-Chun Tseng, Yu-Ju Chen, Yi-Chi Ho, Chian-Feng Chen, Zee-Fen Chang The appropriate supply of dNTPs is critical for cell growth and genome integrity. Here, we investigated the interrelationship between dUTP pyrophosphatase (dUTPase) and ribonucleotide reductase (RNR) in the regulation of genome stability. Our results demonstrate that reducing the expression of dUTPase increases genome stress in cancer. Analysis of clinical samples reveals a significant correlation between the combination of low dUTPase and high R2, a subunit of RNR, and a poor prognosis in colorectal and breast cancer patients. Furthermore, overexpression of R2 in non-tumorigenic cells progressively increases genome stress, promoting transformation. These cells display alterations in replication fork progression, elevated genomic uracil, and breaks at AT-rich common fragile sites. Consistently, overexpression of dUTPase abolishes R2-induced genome instability. Thus, the expression level of dUTPase determines the role of high R2 in driving genome instability in cancer cells. Graphical abstract Teaser Chen et al. show that the expression of dUTPase determines whether elevation of the ribonucleotide reductase subunit R2 can lead to genome stress and chromosomal instability. Furthermore, the combination of low dUTPase and high R2 in clinical tumor samples predicts poor survival in patients with colorectal cancer or breast cancers.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Hermann Broder Schmidt, Rajat Rohatgi Eukaryotic cells contain membrane-less organelles, including nucleoli and stress granules, that behave like liquid droplets. Such endogenous condensates often have internal substructure, but how this is established in the absence of membrane encapsulation remains unclear. We find that the N- and C-terminal domains of TDP43, a heterogeneous nuclear ribonucleoprotein implicated in neurodegenerative diseases, are capable of driving the formation of sub-structured liquid droplets in vivo. These droplets contain dynamic internal “bubbles” of nucleoplasm, reminiscent of membrane-based multi-vesicular endosomes. A conserved sequence embedded within the intrinsically disordered region (IDR) of TDP43 promotes the formation of these multi-phase assemblies. Disease-causing point mutations in the IDR can change the propensity to form bubbles, protein dynamics within the phase, or phase-environment exchange rates. Our results show that a single IDR-containing protein can nucleate the assembly of compartmentalized liquid droplets approximating the morphological complexity of membrane-bound organelles. Graphical abstract Teaser Membrane-less organelles generated through liquid-liquid phase separation play important roles in sub-cellular organization. Schmidt and Rohatgi find that an intrinsically disordered protein domain can nucleate the assembly of multi-phase liquid droplets with dynamic, vesicle-like internal vacuoles that approach the morphological complexity of membrane-bound structures like multi-vesicular bodies.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Vidhya R. Nair, Luis H. Franco, Vineetha M. Zacharia, Haaris S. Khan, Chelsea E. Stamm, Wu You, Denise K. Marciano, Hideo Yagita, Beth Levine, Michael U. Shiloh The prevailing paradigm is that tuberculosis infection is initiated when patrolling alveolar macrophages and dendritic cells within the terminal alveolus ingest inhaled Mycobacterium tuberculosis (Mtb). However, definitive data for this model are lacking. Among the epithelial cells of the upper airway, a specialized epithelial cell known as a microfold cell (M cell) overlies various components of mucosa-associated lymphatic tissue. Here, using multiple mouse models, we show that Mtb invades via M cells to initiate infection. Intranasal Mtb infection in mice lacking M cells either genetically or by antibody depletion resulted in reduced invasion and dissemination to draining lymph nodes. M cell-depleted mice infected via aerosol also had delayed dissemination to lymph nodes and reduced mortality. Translocation of Mtb across two M cell transwell models was rapid and transcellular. Thus, M cell translocation is a vital entry mechanism that contributes to the pathogenesis of Mtb. Graphical abstract Teaser Mycobacterium tuberculosis is an aerosol pathogen that can disseminate from the airways. Nair et al. report that airway M cells actively translocate M. tuberculosis to initiate infection. Depletion of M cells prevents M. tuberculosis dissemination from the mucosa and delays mortality in mice.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Mark D. Borromeo, Trisha K. Savage, Rahul K. Kollipara, Min He, Alexander Augustyn, Jihan K. Osborne, Luc Girard, John D. Minna, Adi F. Gazdar, Melanie H. Cobb, Jane E. Johnson Small cell lung carcinoma (SCLC) is a high-grade pulmonary neuroendocrine tumor. The transcription factors ASCL1 and NEUROD1 play crucial roles in promoting malignant behavior and survival of human SCLC cell lines. Here, we find that ASCL1 and NEUROD1 identify heterogeneity in SCLC, bind distinct genomic loci, and regulate mostly distinct genes. ASCL1, but not NEUROD1, is present in mouse pulmonary neuroendocrine cells, and only ASCL1 is required in vivo for tumor formation in mouse models of SCLC. ASCL1 targets oncogenic genes including MYCL1 , RET , SOX2 , and NFIB while NEUROD1 targets MYC . ASCL1 and NEUROD1 regulate different genes that commonly contribute to neuronal function. ASCL1 also regulates multiple genes in the NOTCH pathway including DLL3 . Together, ASCL1 and NEUROD1 distinguish heterogeneity in SCLC with distinct genomic landscapes and distinct gene expression programs. Graphical abstract Teaser Borromeo et al. reveal heterogeneity in neuroendocrine lung cancers (SCLC) through the lineage-specific transcription factors ASCL1 and NEUROD1. These related factors regulate largely distinct gene programs and differentially regulate key oncogenes in SCLC. ASCL1, but not NEUROD1, is required for tumor formation in current mouse models of SCLC.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Fang Du, Abhishek V. Garg, Karis Kosar, Saikat Majumder, David G. Kugler, Gerard Hernandez Mir, Maria Maggio, Matthew Henkel, Adam Lacy-Hulbert, Mandy J. McGeachy Interleukin-23 (IL-23) is required for inflammatory Th17 cell function in experimental autoimmune encephalomyelitis (EAE), and IL-23 blockade reduces the number of effector Th17 cells in the CNS. We report that pro-inflammatory Th17 cells express high integrin β 3 that is IL-23 dependent. Integrin β 3 was not upregulated on all activated T cells; rather, integrin β 3 was upregulated along with its functional partner integrin α v on effector Th17 cells and “ex-Th17” cells, and α v β 3 hi RORγt + cells expanded during EAE. Integrin α v β 3 inhibitors ameliorated clinical signs of EAE, and integrin β 3 deficiency on CD4 + T cells alone was sufficient to block EAE induction. Furthermore, integrin-β 3 -deficient Th17 cells, but not Th1 cells, were impaired in their ability to induce EAE. Integrin β 3 −/− T cells induced smaller demyelinated lesions and showed reduced spread and accumulation within the CNS, corresponding with impaired extracellular-matrix-mediated migration. Hence, integrin β 3 is required for Th17 cell-mediated autoimmune CNS inflammation. Graphical abstract Teaser Du et al. demonstrate that pro-inflammatory Th17 cells express the receptor integrin αvβ3 on their surface. Using inhibitors and genetically deficient mice, they show that αvβ3 is required for Th17 cells to induce inflammation in the mouse model of multiple sclerosis by promoting migration in the CNS.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Qiangqiang Zhang, Yue Zhang, Chunyang Wang, Zhejun Xu, Qifei Liang, Lei An, Jiwen Li, Zhidong Liu, Yan You, Miao He, Ying Mao, Bin Chen, Zhi-Qi Xiong, John L. Rubenstein, Zhengang Yang Striatal medium-sized spiny neurons (MSNs), composed of striatonigral and striatopallidal neurons, are derived from the lateral ganglionic eminence (LGE). We find that the transcription factor Sp9 is expressed in LGE progenitors that generate nearly all striatal MSNs and that Sp9 expression is maintained in postmitotic striatopallidal MSNs. Sp9 -null mice lose most striatopallidal MSNs because of decreased proliferation of striatopallidal MSN progenitors and increased Bax -dependent apoptosis, whereas the development of striatonigral neurons is largely unaffected. ChIP qPCR provides evidence that Ascl1 directly binds the Sp9 promoter. RNA-seq and in situ hybridization reveal that Sp9 promotes expression of Adora2a , P2ry1 , Gpr6 , and Grik3 in the LGE and striatum. Thus, Sp9 is crucial for the generation, differentiation, and survival of striatopallidal MSNs. Graphical abstract Teaser Zhang et al. analyze Sp9 constitutive and conditional knockout mice and find that this zinc finger transcription factor is critical for the proliferation, differentiation, and survival of striatopallidal projection neurons. The development of striatonigral projection neurons is, in contrast, largely unaffected by the absence of Sp9.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Christian Hauer, Jana Sieber, Thomas Schwarzl, Ina Hollerer, Tomaz Curk, Anne-Marie Alleaume, Matthias W. Hentze, Andreas E. Kulozik The exon junction complex (EJC) connects spliced mRNAs to posttranscriptional processes including RNA localization, transport, and regulated degradation. Here, we provide a comprehensive analysis of bona fide EJC binding sites across the transcriptome including all four RNA binding EJC components eIF4A3, BTZ, UPF3B, and RNPS1. Integration of these data sets permits definition of high-confidence EJC deposition sites as well as assessment of whether EJC heterogeneity drives alternative nonsense-mediated mRNA decay pathways. Notably, BTZ (MLN51 or CASC3) emerges as the EJC subunit that is almost exclusively bound to sites 20–24 nucleotides upstream of exon-exon junctions, hence defining EJC positions. By contrast, eIF4A3, UPF3B, and RNPS1 display additional RNA binding sites suggesting accompanying non-EJC functions. Finally, our data show that EJCs are largely distributed across spliced RNAs in an orthodox fashion, with two notable exceptions: an EJC deposition bias in favor of alternatively spliced transcripts and against the mRNAs that encode ribosomal proteins. Graphical abstract Teaser Exon junction complexes govern multiple critical decisions in posttranscriptional gene regulation. Using all four RNA binding subunits of the complex, Hauer et al. provide a comprehensive map of bona fide EJCs across a mammalian transcriptome and show enrichment on alternatively spliced mRNAs and underrepresentation on RNAs encoding ribosomal proteins.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Julia C. Liu, Jie Liu, Kira M. Holmström, Sara Menazza, Randi J. Parks, Maria M. Fergusson, Zu-Xi Yu, Danielle A. Springer, Charles Halsey, Chengyu Liu, Elizabeth Murphy, Toren Finkel MICU1 is a component of the mitochondrial calcium uniporter, a multiprotein complex that also includes MICU2, MCU, and EMRE. Here, we describe a mouse model of MICU1 deficiency. MICU1 −/− mitochondria demonstrate altered calcium uptake, and deletion of MICU1 results in significant, but not complete, perinatal mortality. Similar to afflicted patients, viable MICU1 −/− mice manifest marked ataxia and muscle weakness. Early in life, these animals display a range of biochemical abnormalities, including increased resting mitochondrial calcium levels, altered mitochondrial morphology, and reduced ATP. Older MICU1 −/− mice show marked, spontaneous improvement coincident with improved mitochondrial calcium handling and an age-dependent reduction in EMRE expression. Remarkably, deleting one allele of EMRE helps normalize calcium uptake while simultaneously rescuing the high perinatal mortality observed in young MICU1 −/− mice. Together, these results demonstrate that MICU1 serves as a molecular gatekeeper preventing calcium overload and suggests that modulating the calcium uniporter could have widespread therapeutic benefits. Graphical abstract Teaser Liu et al. describe the physiological effects of deleting MICU1, a key component of the mitochondrial calcium uniporter. MICU1 −/− mice demonstrate in vivo calcium overload, mirroring what has been described recently for MICU1-deficient human patients. These animals can be rescued by reducing the expression of EMRE, another uniporter component.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Meera Shah, Dan Su, Judith S. Scheliga, Tomáš Pluskal, Susanna Boronat, Khatereh Motamedchaboki, Alexandre Rosa Campos, Feng Qi, Elena Hidalgo, Mitsuhiro Yanagida, Dieter A. Wolf The multi-subunit eukaryotic translation initiation factor eIF3 is thought to assist in the recruitment of ribosomes to mRNA. The expression of eIF3 subunits is frequently disrupted in human cancers, but the specific roles of individual subunits in mRNA translation and cancer remain elusive. Using global transcriptomic, proteomic, and metabolomic profiling, we found a striking failure of Schizosaccharomyces pombe cells lacking eIF3e and eIF3d to synthesize components of the mitochondrial electron transport chain, leading to a defect in respiration, endogenous oxidative stress, and premature aging. Energy balance was maintained, however, by a switch to glycolysis with increased glucose uptake, upregulation of glycolytic enzymes, and strict dependence on a fermentable carbon source. This metabolic regulatory function appears to be conserved in human cells where eIF3e binds metabolic mRNAs and promotes their translation. Thus, via its eIF3d-eIF3e module, eIF3 orchestrates an mRNA-specific translational mechanism controlling energy metabolism that may be disrupted in cancer. Graphical abstract Teaser eIF3 is frequently dysregulated in cancer. Shah et al. show that lack of eIF3d and eIF3e results in impaired synthesis of mitochondrial OXPHOS proteins, respiratory deficiency, glycolytic switch, oxidative stress, and reduced lifespan. Thus, the eIF3d-eIF3e module mediates mRNA-specific translational control of energy metabolism that may be disrupted in cancer.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Pravesh Gupta, Si Min Lai, Jianpeng Sheng, Piotr Tetlak, Akhila Balachander, Carla Claser, Laurent Renia, Klaus Karjalainen, Christiane Ruedl Tissue macrophages exhibit diverse functions, ranging from the maintenance of tissue homeostasis, including clearance of senescent erythrocytes and cell debris, to modulation of inflammation and immunity. Their contribution to the control of blood-stage malaria remains unclear. Here, we show that in the absence of tissue-resident CD169 + macrophages, Plasmodium berghei ANKA (PbA) infection results in significantly increased parasite sequestration, leading to vascular occlusion and leakage and augmented tissue deposition of the malarial pigment hemozoin. This leads to widespread tissue damage culminating in multiple organ inflammation. Thus, the capacity of CD169 + macrophages to contain the parasite burden and its sequestration into different tissues and to limit infection-induced inflammation is crucial to mitigating Plasmodium infection and pathogenesis. Graphical abstract Teaser Using an animal model of blood-stage malaria, Ruedl et al. demonstrate that a distinct innate immune cell type, the tissue-resident CD169 + macrophage, controls parasite propagation and sequestration and restrains inflammation. In the absence of these macrophages, Plasmodium infection is lethal in the model as a result of multiple organ damage.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Shwu-Yuan Wu, Dawn Sijin Nin, A-Young Lee, Scott Simanski, Thomas Kodadek, Cheng-Ming Chiang Post-translational modification can modulate protein conformation and alter binding partner recruitment within gene regulatory regions. Here, we report that bromodomain-containing protein 4 (BRD4), a transcription co-factor and chromatin regulator, uses a phosphorylation-induced switch mechanism to recruit E2 protein encoded by cancer-associated human papillomavirus (HPV) to viral early gene and cellular matrix metalloproteinase-9 ( MMP-9 ) promoters. Enhanced MMP-9 expression, induced upon keratinocyte differentiation, occurs via BRD4-dependent recruitment of active AP-1 and NF-κB to their target sequences. This is triggered by replacement of AP-1 family members JunB and JunD by c-Jun and by re-localization of NF-κB from the cytoplasm to the nucleus. In addition, BRD4 phosphorylation is critical for E2- and origin-dependent HPV DNA replication. A class of phospho-BRD4-targeting compounds, distinct from the BET bromodomain inhibitors, effectively blocks BRD4 phosphorylation-specific functions in transcription and factor recruitment. Graphical abstract Teaser BET bromodomain inhibitors effectively reverse cancer phenotypes but also alter normal cellular activity. Wu et al. describe a phosphorylated region of BRD4 that is critical for HPV origin replication and interacts with the HPV E2 protein. Compounds targeting phospho-BRD4 block E2-regulated viral and cellular gene transcription.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Richard S. Marshall, Fionn McLoughlin, Richard D. Vierstra The autophagic clearance of 26S proteasomes (proteaphagy) is an important homeostatic mechanism within the ubiquitin system that modulates proteolytic capacity and eliminates damaged particles. Here, we define two proteaphagy routes in yeast that respond to either nitrogen starvation or particle inactivation. Whereas the core autophagic machineries required for Atg8 lipidation and vesiculation are essential for both routes, the upstream Atg1 kinase participates only in starvation-induced proteaphagy. Following inactivation, 26S proteasomes become extensively modified with ubiquitin. Although prior studies with Arabidopsis implicated RPN10 in tethering ubiquitylated proteasomes to ATG8 lining the autophagic membranes, yeast proteaphagy employs the evolutionarily distinct receptor Cue5, which simultaneously binds ubiquitin and Atg8. Proteaphagy of inactivated proteasomes also requires the oligomeric Hsp42 chaperone, suggesting that ubiquitylated proteasomes are directed by Hsp42 to insoluble protein deposit (IPOD)-type structures before encapsulation. Together, Cue5 and Hsp42 provide a quality control checkpoint in yeast directed at recycling dysfunctional 26S proteasomes. Graphical abstract Teaser Marshall et al. find that 26S proteasomes are degraded by autophagy in yeast, a process stimulated by inactivation or nitrogen starvation. Proteasome inhibition is accompanied by both Hsp42-mediated aggregation and ubiquitylation of the complex, which is then targeted to autophagic membranes by the ubiquitin binding autophagy receptor Cue5.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Michael Ngo, Arum Han, Anita Lakatos, Debashis Sahoo, Stephanie J. Hachey, Kipp Weiskopf, Andrew H. Beck, Irving L. Weissman, Alexander D. Boiko The high rate of metastasis and recurrence among melanoma patients indicates the existence of cells within melanoma that have the ability to both initiate metastatic programs and bypass immune recognition. Here, we identify CD47 as a regulator of melanoma tumor metastasis and immune evasion. Protein and gene expression analysis of clinical melanoma samples reveals that CD47, an anti-phagocytic signal, correlates with melanoma metastasis. Antibody-mediated blockade of CD47 coupled with targeting of CD271 + melanoma cells strongly inhibits tumor metastasis in patient-derived xenografts. This therapeutic effect is mediated by drastic changes in the tumor and metastatic site immune microenvironments, both of whichwhich exhibit greatly increased density of differentiated macrophages and significantly fewer inflammatory monocytes, pro-metastatic macrophages (CCR2 + /VEGFR1 + ), and neutrophils, all of which are associated with disease progression. Thus, antibody therapy that activates the innate immune response in combination with selective targeting of CD271 + melanoma cells represents a powerful therapeutic approach against metastatic melanoma. Graphical abstract Teaser Ngo et al. find that metastatic progression in melanoma is associated with overexpression of an anti-phagocytic signal, CD47. Blockade of CD47 and activation of innate immunity via macrophage-induced phagocytosis effectively suppress melanoma metastasis in patient-derived xenografts. Coupled with targeting of CD271 + melanoma cells, this regimen produces the most potent therapeutic response.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Hui Zhang, Mehmet G. Badur, Ajit S. Divakaruni, Seth J. Parker, Christian Jäger, Karsten Hiller, Anne N. Murphy, Christian M. Metallo Recent studies have suggested that human pluripotent stem cells (hPSCs) depend primarily on glycolysis and only increase oxidative metabolism during differentiation. Here, we demonstrate that both glycolytic and oxidative metabolism can support hPSC growth and that the metabolic phenotype of hPSCs is largely driven by nutrient availability. We comprehensively characterized hPSC metabolism by using 13 C/ 2 H stable isotope tracing and flux analysis to define the metabolic pathways supporting hPSC bioenergetics and biosynthesis. Although glycolytic flux consistently supported hPSC growth, chemically defined media strongly influenced the state of mitochondrial respiration and fatty acid metabolism. Lipid deficiency dramatically reprogramed pathways associated with fatty acid biosynthesis and NADPH regeneration, altering the mitochondrial function of cells and driving flux through the oxidative pentose phosphate pathway. Lipid supplementation mitigates this metabolic reprogramming and increases oxidative metabolism. These results demonstrate that self-renewing hPSCs can present distinct metabolic states and highlight the importance of medium nutrients on mitochondrial function and development. Graphical abstract Teaser Zhang et al. apply metabolic flux analysis to comprehensively characterize the metabolism of human pluripotent stem cells cultured in different media. Cells maintained in chemically defined media significantly upregulate lipid biosynthesis and redox pathways to compensate for medium lipid deficiency while downregulating oxidative mitochondrial metabolism.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Thomas Laeger, Diana C. Albarado, Susan J. Burke, Lexus Trosclair, John W. Hedgepeth, Hans-Rudolf Berthoud, Thomas W. Gettys, J. Jason Collier, Heike Münzberg, Christopher D. Morrison FGF21 contributes to the metabolic response to dietary protein restriction, and prior data implicate GCN2 as the amino acid sensor linking protein restriction to FGF21 induction. Here, we demonstrate the persistent and essential role of FGF21 in the metabolic response to protein restriction. We show that Fgf21 KO mice are fully resistant to low protein (LP)-induced changes in food intake, energy expenditure (EE), body weight gain, and metabolic gene expression for 6 months. Gcn2 KO mice recapitulate this phenotype, but LP-induced effects on food intake, EE, and body weight subsequently begin to appear after 14 days on diet. We show that this delayed emergence of LP-induced metabolic effects in Gcn2 KO mice coincides with a delayed but progressive increase of hepatic Fgf21 expression and blood FGF21 concentrations over time. These data indicate that FGF21 is essential for the metabolic response to protein restriction but that GCN2 is only transiently required for LP-induced FGF21. Graphical abstract Teaser Laeger et al. demonstrate that FGF21 is required for adaptive metabolic responses to protein restriction. The amino acid sensor GCN2 initially contributes to the induction of FGF21, but additional mechanisms compensate for its absence over longer periods.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Caleb C. Lord, Daniel Ferguson, Gwynneth Thomas, Amanda L. Brown, Rebecca C. Schugar, Amy Burrows, Anthony D. Gromovsky, Jenna Betters, Chase Neumann, Jessica Sacks, Stephanie Marshall, Russell Watts, Martina Schweiger, Richard G. Lee, Rosanne M. Crooke, Mark J. Graham, Justin D. Lathia, Takuya F. Sakaguchi, Richard Lehner, Guenter Haemmerle, Rudolf Zechner, J. Mark Brown Adipose triglyceride lipase (ATGL) and comparative gene identification 58 (CGI-58) are critical regulators of triacylglycerol (TAG) turnover. CGI-58 is thought to regulate TAG mobilization by stimulating the enzymatic activity of ATGL. However, it is not known whether this coactivation function of CGI-58 occurs in vivo. Moreover, the phenotype of human CGI-58 mutations suggests ATGL-independent functions. Through direct comparison of mice with single or double deficiency of CGI-58 and ATGL, we show here that CGI-58 knockdown causes hepatic steatosis in both the presence and absence of ATGL. CGI-58 also regulates hepatic diacylglycerol (DAG) and inflammation in an ATGL-independent manner. Interestingly, ATGL deficiency, but not CGI-58 deficiency, results in suppression of the hepatic and adipose de novo lipogenic program. Collectively, these findings show that CGI-58 regulates hepatic neutral lipid storage and inflammation in the genetic absence of ATGL, demonstrating that mechanisms driving TAG lipolysis in hepatocytes differ significantly from those in adipocytes. Graphical abstract Teaser Comparative gene identification 58 (CGI-58) is thought to regulate triacylglycerol mobilization by stimulating the enzymatic activity of adipose triglyceride lipase (ATGL). Lord et al. now show that CGI-58 regulates hepatic triacylglycerol turnover and inflammation in the genetic absence of ATGL, demonstrating an ATGL-independent role for CGI-58 in mouse liver.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Jordan P. Hamm, Rafael Yuste Patients with schizophrenia have deficient sensory processing, undermining how they perceive and relate to a changing environment. This impairment can be captured by the reduced mismatch negativity (MMN) index, an electroencephalographic biomarker of psychosis. The biological factors contributing to MMN are unclear, though mouse research, in which genetic and optical methods could be applied, has given some insight. Using fast two-photon calcium imaging and multielectrode recordings in awake mice, we find that visual cortical circuits display adapted (decreased) responses to repeated stimuli and amplified responses to a deviant stimulus, the key component of human MMN. Moreover, pharmacogenetic silencing of somatostatin-containing interneurons specifically eliminated this amplification, along with its associated theta/alpha-band response, leaving stimulus-specific adaption and related gamma-band modulations intact. Our results validate a mouse model of MMN and suggest that abnormalities in somatostatin-containing interneurons cause sensory deficits underlying MMN and schizophrenia. Graphical abstract Teaser Hamm and Yuste develop a mouse model of mismatch negativity, a classic EEG biomarker of schizophrenia. They pinpoint two components of this marker within visual cortex (adaptation and deviance detection); revealing that pharmacogenetic suppression of somatostatin inhibitory neurons specifically eliminates deviance detection, the higher-order component critically deficient in patients.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Margherita Puppo, Gabriele Bucci, Martina Rossi, Matteo Giovarelli, Domenico Bordo, Arfa Moshiri, Franco Gorlero, Roberto Gherzi, Paola Briata Epithelial-to-mesenchymal transition (EMT) confers several traits to cancer cells that are required for malignant progression. Here, we report that miR-27b-3p-mediated silencing of the single-strand RNA binding protein KHSRP is required for transforming growth factor β (TGF-β)-induced EMT in mammary gland cells. Sustained KHSRP expression limits TGF-β-dependent induction of EMT factors and cell migration, whereas its knockdown in untreated cells mimics TGF-β-induced EMT. Genome-wide sequencing analyses revealed that KHSRP controls (1) levels of mature miR-192-5p, a microRNA that targets a group of EMT factors, and (2) alternative splicing of a cohort of pre-mRNAs related to cell adhesion and motility including Cd44 and Fgfr2 . KHSRP belongs to a ribonucleoprotein complex that includes hnRNPA1, and the two proteins cooperate in promoting epithelial-type exon usage of select pre-mRNAs. Thus, TGF-β-induced KHSRP silencing is central in a pathway leading to gene-expression changes that contribute to the cellular changes linked to EMT. Graphical abstract Teaser Puppo et al. show that KHSRP, through influencing miR-192-5p maturation as well as alternative splicing of a cohort of pre-mRNAs, is crucial to maintaining the epithelial identity of mammary gland cells. TGF-β-induced KHSRP silencing causes gene expression changes that contribute to EMT.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Diogo Ribeiro, Marcus D.R. Klarqvist, Ulrica K. Westermark, Ganna Oliynyk, Johanna Dzieran, Anna Kock, Carolina Savatier Banares, Falk Hertwig, John Inge Johnsen, Matthias Fischer, Per Kogner, Jakob Lovén, Marie Arsenian Henriksson MYCN amplification and MYC signaling are associated with high-risk neuroblastoma with poor prognosis. Treating these tumors remains challenging, although therapeutic approaches stimulating differentiation have generated considerable interest. We have previously shown that the MYCN-regulated miR-17∼92 cluster inhibits neuroblastoma differentiation by repressing estrogen receptor alpha. Here, we demonstrate that this microRNA (miRNA) cluster selectively targets several members of the nuclear hormone receptor (NHR) superfamily, and we present a unique NHR signature associated with the survival of neuroblastoma patients. We found that suppressing glucocorticoid receptor (GR) expression in MYCN-driven patient and mouse tumors was associated with an undifferentiated phenotype and decreased survival. Importantly, MYCN inhibition and subsequent reactivation of GR signaling promotes neural differentiation and reduces tumor burden. Our findings reveal a key role for the miR-17∼92-regulated NHRs in neuroblastoma biology, thereby providing a potential differentiation approach for treating neuroblastoma patients. Graphical abstract Teaser Ribeiro et al. show that expression of several nuclear hormone receptors is inhibited by the MYCN-regulated miR-17∼92 cluster in MYCN -amplified neuroblastoma. Furthermore, they demonstrate that activation of glucocorticoid signaling results in neural differentiation and reduced tumor burden. Together, these results suggest restoration of nuclear hormone signaling as a putative future therapy for neuroblastoma.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Neil A. Barrett, Camille Malouf, Chrysa Kapeni, Wendi A. Bacon, George Giotopoulos, Sten Eirik W. Jacobsen, Brian J. Huntly, Katrin Ottersbach MLL-AF4+ infant B cell acute lymphoblastic leukemia is characterized by an early onset and dismal survival. It initiates before birth, and very little is known about the early stages of the disease’s development. Using a conditional Mll-AF4-expressing mouse model in which fusion expression is targeted to the earliest definitive hematopoietic cells generated in the mouse embryo, we demonstrate that Mll-AF4 imparts enhanced B lymphoid potential and increases repopulation and self-renewal capacity during a putative pre-leukemic state. This occurs between embryonic days 12 and 14 and manifests itself most strongly in the lymphoid-primed multipotent progenitor population, thus pointing to a window of opportunity and a potential cell of origin. However, this state alone is insufficient to generate disease, with the mice succumbing to B cell lymphomas only after a long latency. Future analysis of the molecular details of this pre-leukemic state will shed light on additional events required for progression to acute leukemia. Graphical abstract Teaser Barrett et al. describe the changes in pre-natal hematopoiesis induced by the Mll-AF4 oncogene in vivo. These include enhanced B lymphoid potential, an expansion of pro-B cells, and increased self-renewal. The authors identify the midgestation lymphoid-primed multipotent progenitor as a potential cell of origin.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Hidekazu Ishida, Rie Saba, Ioannis Kokkinopoulos, Masakazu Hashimoto, Osamu Yamaguchi, Sonja Nowotschin, Manabu Shiraishi, Prashant Ruchaya, Duncan Miller, Stephen Harmer, Ariel Poliandri, Shigetoyo Kogaki, Yasushi Sakata, Leo Dunkel, Andrew Tinker, Anna-Katerina Hadjantonakis, Yoshiki Sawa, Hiroshi Sasaki, Keiichi Ozono, Ken Suzuki, Kenta Yashiro A surface marker that distinctly identifies cardiac progenitors (CPs) is essential for the robust isolation of these cells, circumventing the necessity of genetic modification. Here, we demonstrate that a Glycosylphosphatidylinositol-anchor containing neurotrophic factor receptor, Glial cell line-derived neurotrophic factor receptor alpha 2 ( Gfra2 ), specifically marks CPs. GFRA2 expression facilitates the isolation of CPs by fluorescence activated cell sorting from differentiating mouse and human pluripotent stem cells. Gfra2 mutants reveal an important role for GFRA2 in cardiomyocyte differentiation and development both in vitro and in vivo. Mechanistically, the cardiac GFRA2 signaling pathway is distinct from the canonical pathway dependent on the RET tyrosine kinase and its established ligands. Collectively, our findings establish a platform for investigating the biology of CPs as a foundation for future development of CP transplantation for treating heart failure. Graphical abstract Teaser Ishida et al. show that GPI-anchored neurotrophic factor receptor Gfra2 specifically marks cardiac progenitor cells (CPs) in mouse and human, providing a method for isolating CPs. Unexpectedly, Gfra2 plays a significant role in heart development via a non-canonical signaling pathway that is independent of known ligands and the co-receptor RET tyrosine kinase.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Xuchen Zhang, Qian Li, Lianzhang Wang, Zhong-Jian Liu, Yi Zhong Repeated learning is used daily and is a powerful way to improve memory. A fundamental question is how multiple learning trials add up to improve memory. While the major studies so far of such a repetition effect have emphasized the strengthening of memory formation, the current study reveals a molecular mechanism through suppression of forgetting. We find that single-session training leads to formation of anesthesia-resistant memory (ARM) and then activation of the small G protein Cdc42 to cause decay or forgetting of ARM within 24 hr. Repetition suppresses the activation of Cdc42-dependent forgetting, instead of enhancing ARM formation, leading to prolonged ARM. Consistently, inhibition of Cdc42 activity through genetic manipulation mimicked the repetition effect, while repetition-induced ARM improvement was abolished by elevated Cdc42 activity. Thus, only the first session in repetitive training contributes to ARM formation, while the subsequent sessions are devoted not to acquiring information but to inhibiting forgetting. Graphical abstract Teaser Forgetting is mediated through multiple biological mechanisms. Zhang et al. find that Cdc42 specifically regulates forgetting of anesthesia-resistant memory (ARM) without affecting other known memory components in Drosophila . Repeated learning prolongs ARM retention through suppression of Cdc42-dependent forgetting.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Aeri Cho, Masato Kato, Tess Whitwam, Ji Hoon Kim, Denise J. Montell A longstanding mystery has been the absence of cytoplasmic intermediate filaments (IFs) from Drosophila despite their importance in other organisms. In the course of characterizing the in vivo expression and functions of Drosophila Tropomyosin (Tm) isoforms, we discovered an essential but unusual product of the Tm1 locus, Tm1-I/C, which resembles an IF protein in some respects. Like IFs, Tm1-I/C spontaneously forms filaments in vitro that are intermediate in diameter between F-actin and microtubules. Like IFs but unlike canonical Tms, Tm1-I/C contains N- and C-terminal low-complexity domains flanking a central coiled coil. In vivo, Tm1-I/C forms cytoplasmic filaments that do not associate with F-actin or canonical Tms. Tm1-I/C is essential for collective border cell migration, in epithelial cells for proper cytoarchitecture, and in the germline for the formation of germ plasm. These results suggest that flies have evolved a distinctive type of cytoskeletal filament from Tm. Graphical abstract Teaser Most arthropods lack cytoplasmic intermediate filaments (IFs). While characterizing Drosophila Tropomyosins, Cho et al. find an essential but unusual isoform that resembles IFs. It contains a central coiled coil flanked by low-complexity domains, forms filaments in vitro and in vivo, and does not co-localize with F-actin or canonical Tropomyosins.

Beschreibung: Publication date: Available online 7 July 2016 Source: Cell Reports Author(s): Tim N. Beck, Vladislav A. Korobeynikov, Alexander E. Kudinov, Rachel Georgopoulos, Nehal R. Solanki, Magda Andrews-Hoke, Timothy M. Kistner, David Pépin, Patricia K. Donahoe, Emmanuelle Nicolas, Margret B. Einarson, Yan Zhou, Yanis Boumber, David A. Proia, Ilya G. Serebriiskii, Erica A. Golemis Anti-Müllerian hormone (AMH) and its type II receptor AMHR2, both previously thought to primarily function in gonadal tissue, were unexpectedly identified as potent regulators of transforming growth factor (TGF-β)/bone morphogenetic protein (BMP) signaling and epithelial-mesenchymal transition (EMT) in lung cancer. AMH is a TGF-β/BMP superfamily member, and AMHR2 heterodimerizes with type I receptors (ALK2, ALK3) also used by the type II receptor for BMP (BMPR2). AMH signaling regulates expression of BMPR2, ALK2, and ALK3, supports protein kinase B-nuclear factor κB (AKT-NF-κB) and SMAD survival signaling, and influences BMP-dependent signaling in non-small cell lung cancer (NSCLC). AMH and AMHR2 are selectively expressed in epithelial versus mesenchymal cells, and loss of AMH/AMHR2 induces EMT. Independent induction of EMT reduces expression of AMH and AMHR2. Importantly, EMT associated with depletion of AMH or AMHR2 results in chemoresistance but sensitizes cells to the heat shock protein 90 (HSP90) inhibitor ganetespib. Recognition of this AMH/AMHR2 axis helps to further elucidate TGF-β/BMP resistance-associated signaling and suggests new strategies for therapeutic targeting of EMT. Graphical abstract Teaser Beck et al. identify active signaling by the TGF-β/BMP superfamily member anti-Müllerian hormone (AMH) and its receptor AMHR2 in non-small cell lung cancer (NSCLC), demonstrating a role for AMH/AMHR2 in influencing the basal and BMP-dependent SMAD signaling that constrains epithelial-mesenchymal transition (EMT) and in regulating drug resistance.

Beschreibung: Publication date: 28 June 2016 Source: Cell Reports, Volume 16, Issue 1 Author(s): Sai Li, Ilona Rissanen, Antra Zeltina, Jussi Hepojoki, Jayna Raghwani, Karl Harlos, Oliver G. Pybus, Juha T. Huiskonen, Thomas A. Bowden

Beschreibung: Publication date: Available online 23 June 2016 Source: Cell Reports Author(s): Jason L.J. Lin, Akihisa Nakagawa, Riley Skeen-Gaar, Wei-Zen Yang, Pei Zhao, Zhe Zhang, Xiao Ge, Shohei Mitani, Ding Xue, Hanna S. Yuan Endonuclease G (EndoG) is a mitochondrial protein that is released from mitochondria and relocated into the nucleus to promote chromosomal DNA fragmentation during apoptosis. Here, we show that oxidative stress causes cell-death defects in C. elegans through an EndoG-mediated cell-death pathway. In response to high reactive oxygen species (ROS) levels, homodimeric CPS-6—the C. elegans homolog of EndoG—is dissociated into monomers with diminished nuclease activity. Conversely, the nuclease activity of CPS-6 is enhanced, and its dimeric structure is stabilized by its interaction with the worm AIF homolog, WAH-1, which shifts to disulfide cross-linked dimers under high ROS levels. CPS-6 thus acts as a ROS sensor to regulate the life and death of cells. Modulation of the EndoG dimer conformation could present an avenue for prevention and treatment of diseases resulting from oxidative stress. Graphical abstract Teaser Lin et al. find that, under oxidative conditions, proapoptotic mitochondrial EndoG dimers shift to monomers with diminished nuclease activity, leading to delayed cell death in C. elegans .

Beschreibung: Publication date: Available online 23 June 2016 Source: Cell Reports Author(s): Blanka Kucejova, Joao Duarte, Santhosh Satapati, Xiaorong Fu, Olga Ilkayeva, Christopher B. Newgard, James Brugarolas, Shawn C. Burgess Dysregulated mitochondrial metabolism during hepatic insulin resistance may contribute to pathophysiologies ranging from elevated glucose production to hepatocellular oxidative stress and inflammation. Given that obesity impairs insulin action but paradoxically activates mTORC1, we tested whether insulin action and mammalian target of rapamycin complex 1 (mTORC1) contribute to altered in vivo hepatic mitochondrial metabolism. Loss of hepatic insulin action for 2 weeks caused increased gluconeogenesis, mitochondrial anaplerosis, tricarboxylic acid (TCA) cycle oxidation, and ketogenesis. However, activation of mTORC1, induced by the loss of hepatic Tsc1 , suppressed these fluxes. Only glycogen synthesis was impaired by both loss of insulin receptor and mTORC1 activation. Mice with a double knockout of the insulin receptor and Tsc1 had larger livers, hyperglycemia, severely impaired glycogen storage, and suppressed ketogenesis, as compared to those with loss of the liver insulin receptor alone. Thus, activation of hepatic mTORC1 opposes the catabolic effects of impaired insulin action under some nutritional states. Graphical abstract Teaser Using in vivo stable isotope tracers, Kucejova et al. find that loss of hepatic insulin action stimulates mitochondrial metabolism and that activation of mTORC1 suppresses mitochondrial metabolism and decreases nutritional flexibility. Together, loss of insulin action and activation of mTORC1 recapitulate certain effects of diet-induced insulin resistance on mitochondrial metabolism.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Andrea Rabellino, Margherita Melegari, Van S. Tompkins, Weina Chen, Brian G. Van Ness, Julie Teruya-Feldstein, Maralice Conacci-Sorrell, Siegfried Janz, Pier Paolo Scaglioni The MYC proto-oncogene is a transcription factor implicated in a broad range of cancers. MYC is regulated by several post-translational modifications including SUMOylation, but the functional impact of this post-translational modification is still unclear. Here, we report that the SUMO E3 ligase PIAS1 SUMOylates MYC. We demonstrate that PIAS1 promotes, in a SUMOylation-dependent manner, MYC phosphorylation at serine 62 and dephosphorylation at threonine 58. These events reduce the MYC turnover, leading to increased transcriptional activity. Furthermore, we find that MYC is SUMOylated in primary B cell lymphomas and that PIAS1 is required for the viability of MYC-dependent B cell lymphoma cells as well as several cancer cell lines of epithelial origin. Finally, Pias1 -null mice display endothelial defects reminiscent of Myc -null mice. Taken together, these results indicate that PIAS1 is a positive regulator of MYC. Graphical abstract Teaser Rabellino et al. find that the SUMO E3 ligase PIAS1 promotes activation of the proto-oncogene MYC in a SUMOylation-dependent manner. PIAS1 is co-expressed with MYC in B cell lymphomas and is required for the viability of MYC-driven B cell lymphoma cells.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Lena S. Mortensen, Silvia J.H. Park, Jiang-bin Ke, Benjamin H. Cooper, Lei Zhang, Cordelia Imig, Siegrid Löwel, Kerstin Reim, Nils Brose, Jonathan B. Demb, Jeong-Seop Rhee, Joshua H. Singer Complexin (Cplx) proteins modulate the core SNARE complex to regulate exocytosis. To understand the contributions of Cplx to signaling in a well-characterized neural circuit, we investigated how Cplx3, a retina-specific paralog, shapes transmission at rod bipolar (RB)→AII amacrine cell synapses in the mouse retina. Knockout of Cplx3 strongly attenuated fast, phasic Ca 2+ -dependent transmission, dependent on local [Ca 2+ ] nanodomains, but enhanced slower Ca 2+ -dependent transmission, dependent on global intraterminal [Ca 2+ ] ([Ca 2+ ] I ). Surprisingly, coordinated multivesicular release persisted at Cplx3 −/− synapses, although its onset was slowed. Light-dependent signaling at Cplx3 −/− RB→AII synapses was sluggish, owing largely to increased asynchronous release at light offset. Consequently, propagation of RB output to retinal ganglion cells was suppressed dramatically. Our study links Cplx3 expression with synapse and circuit function in a specific retinal pathway and reveals a role for asynchronous release in circuit gain control. Graphical abstract Teaser Mortensen et al. link complexin-3-dependent synaptic dynamics at rod bipolar cell ribbon synapses to downstream retinal circuit function during rod-mediated vision. In the absence of complexin 3, enhanced asynchronous release from rod bipolar cells depolarizes the postsynaptic network and hinders transmission at synapses onto retinal ganglion cells.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Riccardo Filadi, Elisa Greotti, Gabriele Turacchio, Alberto Luini, Tullio Pozzan, Paola Pizzo Communication between organelles plays key roles in cell biology. In particular, physical and functional coupling of the endoplasmic reticulum (ER) and mitochondria is crucial for regulation of various physiological and pathophysiological processes. Here, we demonstrate that Presenilin 2 (PS2), mutations in which underlie familial Alzheimer’s disease (FAD), promotes ER-mitochondria coupling only in the presence of mitofusin 2 (Mfn2). PS2 is not necessary for the antagonistic effect of Mfn2 on organelle coupling, although its abundance can tune it. The two proteins physically interact, whereas their homologues Mfn1 and PS1 are dispensable for this interplay. Moreover, PS2 mutants associated with FAD are more effective than the wild-type form in modulating ER-mitochondria tethering because their binding to Mfn2 in mitochondria-associated membranes is favored. We propose a revised model for ER-mitochondria interaction to account for these findings and discuss possible implications for FAD pathogenesis. Graphical abstract Teaser Filadi et al. find that the familial Alzheimer’s disease (FAD)-related protein Presenilin 2, enriched at mitochondria-associated membranes, positively modulates endoplasmic reticulum (ER)-mitochondria coupling by binding to Mitofusin 2 and blocking its negative effects on organelle tethering.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Xiaoming Sun, Yi Shi, Tomohiro Akahoshi, Mamoru Fujiwara, Hiroyuki Gatanaga, Christian Schönbach, Nozomi Kuse, Victor Appay, George F. Gao, Shinichi Oka, Masafumi Takiguchi The mechanistic basis for the progressive accumulation of Y 135 F Nef mutant viruses in the HIV-1-infected population remains poorly understood. Y 135 F viruses carry the 2F mutation within RW8 and RF10, which are two HLA-A ∗ 24:02-restricted superimposed Nef epitopes recognized by distinct and adaptable CD8 + T cell responses. We combined comprehensive analysis of the T cell receptor repertoire and cross-reactive potential of wild-type or 2F RW8- and RF10-specific CD8 + T cells with peptide-MHC complex stability and crystal structure studies. We find that, by affecting direct and water-mediated hydrogen bond networks within the peptide-MHC complex, the 2F mutation reduces both TCR and HLA binding. This suggests an advantage underlying the evolution of the 2F variant with decreased CD8 + T cell efficacy. Our study provides a refined understanding of HIV-1 and CD8 + T cell co-adaptation at the population level. Graphical abstract Teaser Rational design of T cell vaccines requires understanding of T cell and HIV-1 co-evolution. Sun et al. find that a single immune escape mutation has differential impacts on two HIV epitope-specific responses. The mutation alters the ability of the virus to trigger immune responses.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Matilda A. Haas, Linh Ngo, Shan Shan Li, Sibylle Schleich, Zhengdong Qu, Hannah K. Vanyai, Hayley D. Cullen, Aida Cardona-Alberich, Ivan E. Gladwyn-Ng, Alistair T. Pagnamenta, Jenny C. Taylor, Helen Stewart, Usha Kini, Kent E. Duncan, Aurelio A. Teleman, David A. Keays, Julian I.-T. Heng Disruptions to neuronal mRNA translation are hypothesized to underlie human neurodevelopmental syndromes. Notably, the mRNA translation re-initiation factor DENR is a regulator of eukaryotic translation and cell growth, but its mammalian functions are unknown. Here, we report that Denr influences the migration of murine cerebral cortical neurons in vivo with its binding partner Mcts1 , whereas perturbations to Denr impair the long-term positioning, dendritic arborization, and dendritic spine characteristics of postnatal projection neurons. We characterized de novo missense mutations in DENR (p.C37Y and p.P121L) detected in two unrelated human subjects diagnosed with brain developmental disorder to find that each variant impairs the function of DENR in mRNA translation re-initiation and disrupts the migration and terminal branching of cortical neurons in different ways. Thus, our findings link human brain disorders to impaired mRNA translation re-initiation through perturbations in DENR (OMIM: 604550 ) function in neurons. Graphical abstract Teaser Haas et al. report that the expression of the mRNA translation re-initiation factor DENR is important for the radial positioning, dendritic branching, and dendritic spine properties of developing cerebral cortex neurons. Characterization of disease-associated mutations in DENR links impaired mRNA translation re-initiation to human neurological disorders.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): In Young Choi, HoTae Lim, Kenneth Estrellas, Jyothi Mula, Tatiana V. Cohen, Yuanfan Zhang, Christopher J. Donnelly, Jean-Philippe Richard, Yong Jun Kim, Hyesoo Kim, Yasuhiro Kazuki, Mitsuo Oshimura, Hongmei Lisa Li, Akitsu Hotta, Jeffrey Rothstein, Nicholas Maragakis, Kathryn R. Wagner, Gabsang Lee Duchenne muscular dystrophy (DMD) remains an intractable genetic disease. Althogh there are several animal models of DMD, there is no human cell model that carries patient-specific DYSTROPHIN mutations. Here, we present a human DMD model using human induced pluripotent stem cells (hiPSCs). Our model reveals concordant disease-related phenotypes with patient-dependent variation, which are partially reversed by genetic and pharmacological approaches. Our “chemical-compound-based” strategy successfully directs hiPSCs into expandable myoblasts, which exhibit a myogenic transcriptional program, forming striated contractile myofibers and participating in muscle regeneration in vivo. DMD-hiPSC-derived myoblasts show disease-related phenotypes with patient-to-patient variability, including aberrant expression of inflammation or immune-response genes and collagens, increased BMP/TGFβ signaling, and reduced fusion competence. Furthermore, by genetic correction and pharmacological “dual-SMAD” inhibition, the DMD-hiPSC-derived myoblasts and genetically corrected isogenic myoblasts form “rescued” multi-nucleated myotubes. In conclusion, our findings demonstrate the feasibility of establishing a human “DMD-in-a-dish” model using hiPSC-based disease modeling. Graphical abstract Teaser Choi et al. show that human iPSC (hiPSC)-derived myoblasts from Duchenne muscular dystrophy patients have aberrant phenotypes with patient-to-patient variability. The cells can be partially rescued by either genetic correction or chemical compound treatments.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Yongliang Huo, Timothy Su, Qiuyin Cai, Ian G. Macara The broad implementation of precision medicine in cancer is impeded by the lack of a complete inventory of the genes involved in tumorigenesis. We performed in vivo screening of ∼1,000 genes that are associated with signaling for positive roles in breast cancer, using lentiviral expression vectors in primary MMTV-ErbB2 mammary tissue. Gain of function of five genes, including RET , GTF2IRD1 , ADORA1 , LARS2 , and DPP8 , significantly promoted mammary tumor growth. We further studied one tumor-promoting gene, the transcription factor GTF2IRD1 . The mis-regulation of genes downstream of GTF2IRD1 , including TβR2 and BMPR1b , also individually promoted mammary cancer development, and silencing of TβR2 suppressed GTF2IRD1-driven tumor promotion. In addition, GTF2IRD1 is highly expressed in human breast tumors, correlating with high tumor grades and poor prognosis. Our in vivo approach is readily expandable to whole-genome annotation of tumor-promoting genes. Graphical abstract Teaser Huo et al. screen in vivo for genes that promote mammary tumorigenesis in primary MMTV-ErbB2 mammary tissue. Of five hits, one is a transcription factor, GTF2IRD1 , which promotes mammary cancer through induction of TGFβR2 and downregulation of BMPR1b . GTF2IRD1 expression in human breast cancers correlates with high tumor grades and poor prognosis.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Mauris C. Nnamani, Soumya Ganguly, Eric M. Erkenbrack, Vincent J. Lynch, Laura S. Mizoue, Yingchun Tong, Heather L. Darling, Monika Fuxreiter, Jens Meiler, Günter P. Wagner Transcription factors (TFs) play multiple roles in development. Given this multifunctionality, it has been assumed that TFs are evolutionarily highly constrained. Here, we investigate the molecular mechanisms for the origin of a derived functional interaction between two TFs, HOXA11 and FOXO1. We have previously shown that the regulatory role of HOXA11 in mammalian endometrial stromal cells requires interaction with FOXO1, and that the physical interaction between these proteins evolved before their functional cooperativity. Here, we demonstrate that the derived functional cooperativity between HOXA11 and FOXO1 is due to derived allosteric regulation of HOXA11 by FOXO1. This study shows that TF function can evolve through changes affecting the functional output of a pre-existing protein complex. Graphical abstract Teaser TFs are assumed to be evolutionarily constrained because of their multiple biological roles. In eutherian mammals HOXA11 evolved a derived function regulating genes in the uterus. This function is caused by a neo-allosteric switch in response to interaction with FOXO1, thereby circumventing constraints associated with pleiotropy.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Alexandra M. Pinzaru, Robert A. Hom, Angela Beal, Aaron F. Phillips, Eric Ni, Timothy Cardozo, Nidhi Nair, Jaehyuk Choi, Deborah S. Wuttke, Agnel Sfeir, Eros Lazzerini Denchi Genome sequencing studies have revealed a number of cancer-associated mutations in the telomere-binding factor POT1. Here, we show that when combined with p53 deficiency, depletion of murine POT1a in common lymphoid progenitor cells fosters genetic instability, accelerates the onset, and increases the severity of T cell lymphomas. In parallel, we examined human and mouse cells carrying POT1 mutations found in cutaneous T cell lymphoma (CTCL) patients. Inhibition of POT1 activates ATR-dependent DNA damage signaling and induces telomere fragility, replication fork stalling, and telomere elongation. Our data suggest that these phenotypes are linked to impaired CST (CTC1-STN1-TEN1) function at telomeres. Lastly, we show that proliferation of cancer cells lacking POT1 is enabled by the attenuation of the ATR kinase pathway. These results uncover a role for defective telomere replication during tumorigenesis. Graphical abstract Teaser Pinzaru et al. define a role for POT1 inactivation in the onset of thymic lymphomas. Inhibition of POT1 causes replication defects at telomeres resulting in telomere fragility, replication fork stalling, and genome instability. These results suggest a role for defective telomere replication during tumorigenesis.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Lale Ozcan, Devram S. Ghorpade, Ze Zheng, Jane Cristina de Souza, Ke Chen, Marc Bessler, Melissa Bagloo, Beth Schrope, Richard Pestell, Ira Tabas Defective insulin signaling in hepatocytes is a key factor in type 2 diabetes. In obesity, activation of calcium/calmodulin-dependent protein kinase II (CaMKII) in hepatocytes suppresses ATF6, which triggers a PERK-ATF4-TRB3 pathway that disrupts insulin signaling. Elucidating how CaMKII suppresses ATF6 is therefore essential to understanding this insulin resistance pathway. We show that CaMKII phosphorylates and blocks nuclear translocation of histone deacetylase 4 (HDAC4). As a result, HDAC4-mediated SUMOylation of the corepressor DACH1 is decreased, which protects DACH1 from proteasomal degradation. DACH1, together with nuclear receptor corepressor (NCOR), represses Atf6 transcription, leading to activation of the PERK-TRB3 pathway and defective insulin signaling. DACH1 is increased in the livers of obese mice and humans, and treatment of obese mice with liver-targeted constitutively nuclear HDAC4 or DACH1 small hairpin RNA (shRNA) increases ATF6, improves hepatocyte insulin signaling, and protects against hyperglycemia and hyperinsulinemia. Thus, DACH1-mediated corepression in hepatocytes emerges as an important link between obesity and insulin resistance. Graphical abstract Teaser Ozcan et al. find that CaMKII phosphorylates and blocks nuclear translocation of hepatocyte HDAC4 in obesity. Lower nuclear HDAC4 decreases the SUMOylation and degradation of the corepressor DACH1. Elevated nuclear DACH1 activates an ER stress pathway that causes defective insulin signaling, while silencing of hepatocyte DACH1 in obesity improves insulin sensitivity.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Kevin M. Harlen, Kristine L. Trotta, Erin E. Smith, Mohammad M. Mosaheb, Stephen M. Fuchs, L. Stirling Churchman Transcription controls splicing and other gene regulatory processes, yet mechanisms remain obscure due to our fragmented knowledge of the molecular connections between the dynamically phosphorylated RNA polymerase II (Pol II) C-terminal domain (CTD) and regulatory factors. By systematically isolating phosphorylation states of the CTD heptapeptide repeat (Y 1 S 2 P 3 T 4 S 5 P 6 S 7 ), we identify hundreds of protein factors that are differentially enriched, revealing unappreciated connections between the Pol II CTD and co-transcriptional processes. These data uncover a role for threonine-4 in 3′ end processing through control of the transition between cleavage and termination. Furthermore, serine-5 phosphorylation seeds spliceosomal assembly immediately downstream of 3′ splice sites through a direct interaction with spliceosomal subcomplex U1. Strikingly, threonine-4 phosphorylation also impacts splicing by serving as a mark of co-transcriptional spliceosome release and ensuring efficient post-transcriptional splicing genome-wide. Thus, comprehensive Pol II interactomes identify the complex and functional connections between transcription machinery and other gene regulatory complexes. Graphical abstract Teaser Many RNA-processing events are coupled to transcription. To gain insight into the mechanisms linking these processes, Harlen et al. determine interactomes for each RNA polymerase II phospho-CTD residue, linking CTD Thr4 to transcription termination and CTD Thr4 and Ser5 to splicing.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Alexia Eliades, Sarah Wareing, Elli Marinopoulou, Muhammad Z.H. Fadlullah, Rahima Patel, Joanna B. Grabarek, Berenika Plusa, Georges Lacaud, Valerie Kouskoff It is now well-established that hematopoietic stem cells (HSCs) and progenitor cells originate from a specialized subset of endothelium, termed hemogenic endothelium (HE), via an endothelial-to-hematopoietic transition. However, the molecular mechanisms determining which endothelial progenitors possess this hemogenic potential are currently unknown. Here, we investigated the changes in hemogenic potential in endothelial progenitors at the early stages of embryonic development. Using an ETV2::GFP reporter mouse to isolate emerging endothelial progenitors, we observed a dramatic decrease in hemogenic potential between embryonic day (E)7.5 and E8.5. At the molecular level, Runx1 is expressed at much lower levels in E8.5 intra-embryonic progenitors, while Bmi1 expression is increased. Remarkably, the ectopic expression of Runx1 in these progenitors fully restores their hemogenic potential, as does the suppression of BMI1 function. Altogether, our data demonstrate that hemogenic competency in recently specified endothelial progenitors is restrained through the active silencing of Runx1 expression. Graphical abstract Teaser Hematopoiesis originates from specialized HE at specific stages of embryonic development. Eliades et al. demonstrate that RUNX1 repression is critical for suppressing hemogenic competency in endothelial progenitors at the E8.5 developmental stage and that this is achieved through the silencing of Runx1 transcription by a BMI1-mediated mechanism.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Curtis A. Nutter, Elizabeth A. Jaworski, Sunil K. Verma, Vaibhav Deshmukh, Qiongling Wang, Olga B. Botvinnik, Mario J. Lozano, Ismail J. Abass, Talha Ijaz, Allan R. Brasier, Nisha J. Garg, Xander H.T. Wehrens, Gene W. Yeo, Muge N. Kuyumcu-Martinez Alternative splicing (AS) defects that adversely affect gene expression and function have been identified in diabetic hearts; however, the mechanisms responsible are largely unknown. Here, we show that the RNA-binding protein RBFOX2 contributes to transcriptome changes under diabetic conditions. RBFOX2 controls AS of genes with important roles in heart function relevant to diabetic cardiomyopathy. RBFOX2 protein levels are elevated in diabetic hearts despite low RBFOX2 AS activity. A dominant-negative (DN) isoform of RBFOX2 that blocks RBFOX2-mediated AS is generated in diabetic hearts. DN RBFOX2 interacts with wild-type (WT) RBFOX2, and ectopic expression of DN RBFOX2 inhibits AS of RBFOX2 targets. Notably, DN RBFOX2 expression is specific to diabetes and occurs at early stages before cardiomyopathy symptoms appear. Importantly, DN RBFOX2 expression impairs intracellular calcium release in cardiomyocytes. Our results demonstrate that RBFOX2 dysregulation by DN RBFOX2 is an early pathogenic event in diabetic hearts. Graphical abstract Teaser Nutter et al. show that the majority of transcripts mis-spliced in diabetic hearts have RBFOX2-binding sites. In diabetic hearts, a DN isoform of RBFOX2 with inhibitory splicing function is generated in response to high protein levels of WT RBFOX2. DN RBFOX2 upregulation occurs before cardiac complications manifest.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Madison E. Stellfox, Isaac K. Nardi, Christina M. Knippler, Daniel R. Foltz The Mis18 complex specifies the site of new CENP-A nucleosome assembly by recruiting the CENP-A-specific assembly factor HJURP (Holliday junction recognition protein). The human Mis18 complex consists of Mis18α, Mis18β, and Mis18 binding protein 1 (Mis18BP1/hsKNL2). Although Mis18α and Mis18β are highly homologous proteins, we find that their conserved YIPPEE domains mediate distinct interactions that are essential to link new CENP-A deposition to existing centromeres. We find that Mis18α directly interacts with the N terminus of Mis18BP1, whereas Mis18β directly interacts with CENP-C during G1 phase, revealing that these proteins have evolved to serve distinct functions in centromeres of higher eukaryotes. The N terminus of Mis18BP1, containing both the Mis18α and CENP-C binding domains, is necessary and sufficient for centromeric localization. Therefore, the Mis18 complex contains dual CENP-C recognition motifs that are combinatorially required to generate robust centromeric localization that leads to CENP-A deposition. Graphical abstract Teaser The MIS18 gene is duplicated in the vertebrate lineage. Stellfox et al. show that Mis18α and Mis18β paralogs have diverged to serve different functions within the human centromere. Mis18α binds Mis18BP1, and Mis18β recognizes CENP-C within the centromere. Centromere specification requires the recognition of the existing centromere by the intact Mis18 complex.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): In Young Choi, Laura Piccio, Patra Childress, Bryan Bollman, Arko Ghosh, Sebastian Brandhorst, Jorge Suarez, Andreas Michalsen, Anne H. Cross, Todd E. Morgan, Min Wei, Friedemann Paul, Markus Bock, Valter D. Longo Dietary interventions have not been effective in the treatment of multiple sclerosis (MS). Here, we show that periodic 3-day cycles of a fasting mimicking diet (FMD) are effective in ameliorating demyelination and symptoms in a murine experimental autoimmune encephalomyelitis (EAE) model. The FMD reduced clinical severity in all mice and completely reversed symptoms in 20% of animals. These improvements were associated with increased corticosterone levels and regulatory T (T reg ) cell numbers and reduced levels of pro-inflammatory cytokines, T H 1 and T H 17 cells, and antigen-presenting cells (APCs). Moreover, the FMD promoted oligodendrocyte precursor cell regeneration and remyelination in axons in both EAE and cuprizone MS models, supporting its effects on both suppression of autoimmunity and remyelination. We also report preliminary data suggesting that an FMD or a chronic ketogenic diet are safe, feasible, and potentially effective in the treatment of relapsing-remitting multiple sclerosis (RRMS) patients (NCT01538355). Graphical abstract Teaser Choi et al. show that cycles of a fasting mimicking diet (FMD) ameliorate disease severity by suppressing autoimmunity and stimulating remyelination via oligodendrocyte regeneration in multiple sclerosis (MS) mouse models. They also show that a similar FMD is a safe, feasible, and possibly a potentially effective treatment for patients with relapsing-remitting MS.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Fengshan Liang, Simonne Longerich, Adam S. Miller, Caroline Tang, Olga Buzovetsky, Yong Xiong, David G. Maranon, Claudia Wiese, Gary M. Kupfer, Patrick Sung The UAF1-USP1 complex deubiquitinates FANCD2 during execution of the Fanconi anemia DNA damage response pathway. As such, UAF1 depletion results in persistent FANCD2 ubiquitination and DNA damage hypersensitivity. UAF1-deficient cells are also impaired for DNA repair by homologous recombination. Herein, we show that UAF1 binds DNA and forms a dimeric complex with RAD51AP1, an accessory factor of the RAD51 recombinase, and a trimeric complex with RAD51 through RAD51AP1. Two small ubiquitin-like modifier (SUMO)-like domains in UAF1 and a SUMO-interacting motif in RAD51AP1 mediate complex formation. Importantly, UAF1 enhances RAD51-mediated homologous DNA pairing in a manner that is dependent on complex formation with RAD51AP1 but independent of USP1. Mechanistically, RAD51AP1-UAF1 co-operates with RAD51 to assemble the synaptic complex, a critical nucleoprotein intermediate in homologous recombination, and cellular studies reveal the biological significance of the RAD51AP1-UAF1 protein complex. Our findings provide insights into an apparently USP1-independent role of UAF1 in genome maintenance. Graphical abstract Teaser Liang et al. find that UAF1 has DNA binding activity, define the interaction interface within the RAD51AP1-UAF1 complex, and show that the protein complex works in conjunction with the RAD51 presynaptic filament to mediate DNA pairing in homologous recombination.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Zhiqi Candice Yip, Maxwell G. Heiman Simple cell-cell interactions can give rise to complex cellular patterns. For example, neurons of the same type can interact to create a complex patchwork of non-overlapping dendrite arbors, a pattern known as dendrite tiling. Dendrite tiling often involves mutual repulsion between neighboring neurons. While dendrite tiling is found across nervous systems, the nematode Caenorhabditis elegans has a relatively simple nervous system with few opportunities for tiling. Here, we show that genetic duplication of a single neuron, PVD, is sufficient to create dendrite tiling among the resulting ectopic neurons. We use laser ablation to show that this tiling is mediated by mutual repulsion between neighbors. Furthermore, we find that tiling requires a repulsion signal (UNC-6/Netrin and its receptors UNC-40/DCC and UNC-5) that normally patterns the PVD dendrite arbor. These results demonstrate that an apparently complex cellular pattern can emerge in a simple nervous system merely by increasing neuron number. Graphical abstract Teaser C. elegans does not normally exhibit dendrite tiling by mutual repulsion. Yip and Heiman find that when extra neurons are added to this system, tiling spontaneously emerges from pre-existing pathways for dendrite self-avoidance, suggesting one path through which tiling might have evolved.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Roberto Pagliarini, Raffaele Castello, Francesco Napolitano, Roberta Borzone, Patrizia Annunziata, Giorgia Mandrile, Mario De Marchi, Nicola Brunetti-Pierri, Diego di Bernardo Primary hyperoxaluria type I (PH1) is an autosomal-recessive inborn error of liver metabolism caused by alanine:glyoxylate aminotransferase (AGT) deficiency. In silico modeling of liver metabolism in PH1 recapitulated accumulation of known biomarkers as well as alteration of histidine and histamine levels, which we confirmed in vitro, in vivo, and in PH1 patients. AGT-deficient mice showed decreased vascular permeability, a readout of in vivo histamine activity. Histamine reduction is most likely caused by increased catabolism of the histamine precursor histidine, triggered by rerouting of alanine flux from AGT to the glutamic-pyruvate transaminase (GPT, also known as the alanine-transaminase ALT). Alanine administration reduces histamine levels in wild-type mice, while overexpression of GPT in PH1 mice increases plasma histidine, normalizes histamine levels, restores vascular permeability, and decreases urinary oxalate levels. Our work demonstrates that genome-scale metabolic models are clinically relevant and can link genotype to phenotype in metabolic disorders. Graphical abstract Teaser Pagliarini et al. use a computational model of liver metabolism to predict alterations caused by the loss of alanine:glyoxylate aminotransferase (AGT), resulting in primary hyperoxaluria type I (PH1). In addition to known disease biomarkers, the model predicts a reduction in histidine and histamine levels. GPT overexpression in PH1 mice normalizes histamine and oxalate levels.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Jennifer Chu, Gabriela Galicia-Vázquez, Regina Cencic, John R. Mills, Alexandra Katigbak, John A. Porco, Jerry Pelletier Targeting translation initiation is an emerging anti-neoplastic strategy that capitalizes on de-regulated upstream MAPK and PI3K-mTOR signaling pathways in cancers. A key regulator of translation that controls ribosome recruitment flux is eukaryotic initiation factor (eIF) 4F, a hetero-trimeric complex composed of the cap binding protein eIF4E, the scaffolding protein eIF4G, and the RNA helicase eIF4A. Small molecule inhibitors targeting eIF4F display promising anti-neoplastic activity in preclinical settings. Among these are some rocaglate family members that are well tolerated in vivo, deplete eIF4F of its eIF4A helicase subunit, have shown activity as single agents in several xenograft models, and can reverse acquired resistance to MAPK and PI3K-mTOR targeted therapies. Herein, we highlight the power of using genetic complementation approaches and CRISPR/Cas9-mediated editing for drug-target validation ex vivo and in vivo, linking the anti-tumor properties of rocaglates to eIF4A inhibition. Graphical abstract Teaser Rocaglates are anti-neoplastic agents that are thought to inhibit the RNA helicase eIF4A, although alternative targets have also been proposed. Using a series of biochemical assays and CRISPR/Cas9 genome editing, Chu et al. provide genetic evidence that the anti-neoplastic activities of rocaglates are a consequence of eIF4A1 inhibition.

Beschreibung: Publication date: Available online 26 May 2016 Source: Cell Reports Author(s): Charlotte Proudhon, Valentina Snetkova, Ramya Raviram, Camille Lobry, Sana Badri, Tingting Jiang, Bingtao Hao, Thomas Trimarchi, Yuval Kluger, Iannis Aifantis, Richard Bonneau, Jane A. Skok V(D)J recombination relies on the presence of proximal enhancers that activate the antigen receptor (AgR) loci in a lineage- and stage-specific manner. Unexpectedly, we find that both active and inactive AgR enhancers cooperate to disseminate their effects in a localized and long-range manner. Here, we demonstrate the importance of short-range contacts between active enhancers that constitute an Igk super-enhancer in B cells. Deletion of one element reduces the interaction frequency between other enhancers in the hub, which compromises the transcriptional output of each component. Furthermore, we establish that, in T cells, long-range contact and cooperation between the inactive Igk enhancer MiEκ and the active Tcrb enhancer Eβ alters enrichment of CBFβ binding in a manner that impacts Tcrb recombination. These findings underline the complexities of enhancer regulation and point to a role for localized and long-range enhancer-sharing between active and inactive elements in lineage- and stage-specific control. Graphical abstract Teaser Proudhon et al. show that, in B cells, synergistic chromatin contacts between the individual elements of the Igk super-enhancer contribute to the transcriptional output of all partner enhancers. In T cells, one component of the Igk enhancer cluster cooperates with the Tcrb enhancer to exert control over Tcrb recombination.

Beschreibung: Publication date: Available online 22 March 2016 Source: Cell Reports Author(s): Achuth Padmanabhan, Simone Anh-Thu Vuong, Mark Hochstrasser Targeted intracellular protein degradation in eukaryotes is largely mediated by the proteasome. Here, we report the formation of an alternative proteasome isoform in human cells, previously found only in budding yeast, that bears an altered subunit arrangement in the outer ring of the proteasome core particle. These proteasomes result from incorporation of an additional α4 (PSMA7) subunit in the position normally occupied by α3 (PSMA4). Assembly of “α4-α4” proteasomes depends on the relative cellular levels of α4 and α3 and on the proteasome assembly chaperone PAC3. The oncogenic tyrosine kinases ABL and ARG and the tumor suppressor BRCA1 regulate cellular α4 levels and formation of α4-α4 proteasomes. Cells primed to assemble α4-α4 proteasomes exhibit enhanced resistance to toxic metal ions. Taken together, our results establish the existence of an alternative mammalian proteasome isoform and suggest a potential role in enabling cells to adapt to environmental stresses. Graphical abstract Teaser Padmanabhan et al. demonstrate the formation of an alternative proteasome isoform in human cells. Cells primed to assemble such proteasomes exhibit enhanced resistance to toxic metals, and factors favoring their assembly are observed in certain cancers, suggesting potential roles for this isoform in adaptation to stress and in cancer.

Beschreibung: Publication date: 12 July 2016 Source: Cell Reports, Volume 16, Issue 2 Author(s): Katerina M. Vakaloglou, Georgios Chrysanthis, Maria Anna Rapsomaniki, Zoi Lygerou, Christos G. Zervas

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Xiao Ding, Aibo Wang, Xiaopeng Ma, Maud Demarque, Wei Jin, Huawei Xin, Anne Dejean, Chen Dong Foxp3-expressing regulatory T (Treg) cells are essential for immune tolerance; however, the molecular mechanisms underlying Treg cell expansion and function are still not well understood. SUMOylation is a protein post-translational modification characterized by covalent attachment of SUMO moieties to lysines. UBC9 is the only E2 conjugating enzyme involved in this process, and loss of UBC9 completely abolishes the SUMOylation pathway. Here, we report that selective deletion of Ubc9 within the Treg lineage results in fatal early-onset autoimmunity similar to Foxp3 mutant mice. Ubc9 -deficient Treg cells exhibit severe defects in TCR-driven homeostatic proliferation, accompanied by impaired activation and compromised suppressor function. Importantly, TCR ligation enhanced SUMOylation of IRF4, a critical regulator of Treg cell function downstream of TCR signals, which regulates its stability in Treg cells. Our data thus have demonstrated an essential role of SUMOylation in the expansion and function of Treg cells. Graphical abstract Teaser Ding et al. find that UBC9-mediated protein SUMOylation is required for Treg cell homeostasis, proliferation, activation, and suppressive function by sustaining TCR signaling. The authors identify IRF4 as a SUMO target regulated by TCR-enhanced SUMOylation.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Ozgun Gokce, Geoffrey M. Stanley, Barbara Treutlein, Norma F. Neff, J. Gray Camp, Robert C. Malenka, Patrick E. Rothwell, Marc V. Fuccillo, Thomas C. Südhof, Stephen R. Quake The striatum contributes to many cognitive processes and disorders, but its cell types are incompletely characterized. We show that microfluidic and FACS-based single-cell RNA sequencing of mouse striatum provides a well-resolved classification of striatal cell type diversity. Transcriptome analysis revealed ten differentiated, distinct cell types, including neurons, astrocytes, oligodendrocytes, ependymal, immune, and vascular cells, and enabled the discovery of numerous marker genes. Furthermore, we identified two discrete subtypes of medium spiny neurons (MSNs) that have specific markers and that overexpress genes linked to cognitive disorders and addiction. We also describe continuous cellular identities, which increase heterogeneity within discrete cell types. Finally, we identified cell type-specific transcription and splicing factors that shape cellular identities by regulating splicing and expression patterns. Our findings suggest that functional diversity within a complex tissue arises from a small number of discrete cell types, which can exist in a continuous spectrum of functional states. Graphical abstract Teaser The striatum, the gateway to basal ganglia circuitry, is critical for motor functions. However, its cell types are incompletely characterized. Gokce et al. reveal the diversity of striatal cells using scRNA-seq. They also describe continuous expression gradients within all MSN subtypes and astrocytes that may be fundamental to transcriptional diversity.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Alessandra Maria Casano, Marvin Albert, Francesca Peri In the brain, neurons that fail to assemble into functional circuits are eliminated. Their clearance depends on microglia, immune cells that colonize the CNS during embryogenesis. Despite the importance of these cells in development and disease, the mechanisms that target and position microglia within the brain are unclear. Here we show that, in zebrafish, attraction of microglia into the brain exploits differences in developmental neuronal apoptosis and that these provide a mechanism for microglial distribution. Reducing neuronal cell death results in fewer microglia, whereas increased apoptosis enhances brain colonization, resulting in more microglia at later stages. Interestingly, attraction into the brain depends on nucleotide signaling, the same signaling system used to guide microglia toward brain injuries. Finally, this work uncovers a cell-non-autonomous role for developmental apoptosis. Classically considered a wasteful process, programmed cell death is exploited here to configure the immune-neuronal interface of the brain. Graphical abstract Teaser Casano et al. show that establishment of the microglial population is linked to developmental apoptosis in the brain. Differences in neuronal apoptosis provide a mechanism for entry and positioning of microglial precursors within the brain. Attraction is mediated by nucleotide signaling previously shown to guide microglia toward brain injuries.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Yoshiko Matsumoto-Makidono, Hisako Nakayama, Miwako Yamasaki, Taisuke Miyazaki, Kazuto Kobayashi, Masahiko Watanabe, Masanobu Kano, Kenji Sakimura, Kouichi Hashimoto Some neurons have the ability to enhance output voltage to input current with a preferred frequency, which is called resonance. Resonance is thought to be a basis for membrane potential oscillation. Although ion channels responsible for resonance have been reported, the precise mechanisms by which these channels work remain poorly understood. We have found that resonance is reduced but clearly present in the inferior olivary neurons of Cav3.1 T-type voltage-dependent Ca 2+ channel knockout (KO) mice. The activation of Cav3.1 channels is strongly membrane potential dependent, but less frequency dependent. Residual resonance in Cav3.1 KO mice is abolished by a hyper-polarization-activated cyclic nucleotide-gated (HCN) channel blocker, ZD7288, and is partially suppressed by voltage-dependent K + channel blockers. Resonance is inhibited by ZD7288 in wild-type mice and impaired in HCN1 KO mice, suggesting that the HCN1 channel is essential for resonance. The ZD7288-sensitive current is nearly sinusoidal and strongly frequency dependent. These results suggest that Cav3.1 and HCN1 channels act as amplifying and resonating conductances, respectively. Graphical abstract Teaser Matsumoto-Makidono et al. find that electrical resonance in inferior olivary neurons is mainly mediated by the activation of HCN1 and Cav3.1 channels, which act as frequency-dependent resonating conductance and depolarization-dependent amplifying conductance, respectively.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): David A. Quigley, Eve Kandyba, Phillips Huang, Kyle D. Halliwill, Jonas Sjölund, Facundo Pelorosso, Christine E. Wong, Gillian L. Hirst, Di Wu, Reyno Delrosario, Atul Kumar, Allan Balmain Inherited germline polymorphisms can cause gene expression levels in normal tissues to differ substantially between individuals. We present an analysis of the genetic architecture of normal adult skin from 470 genetically unique mice, demonstrating the effect of germline variants, skin tissue location, and perturbation by exogenous inflammation or tumorigenesis on gene signaling pathways. Gene networks related to specific cell types and signaling pathways, including sonic hedgehog ( Shh ), Wnt , Lgr family stem cell markers, and keratins, differed at these tissue sites, suggesting mechanisms for the differential susceptibility of dorsal and tail skin to development of skin diseases and tumorigenesis. The Pten tumor suppressor gene network is rewired in premalignant tumors compared to normal tissue, but this response to perturbation is lost during malignant progression. We present a software package for expression quantitative trait loci (eQTL) network analysis and demonstrate how network analysis of whole tissues provides insights into interactions between cell compartments and signaling molecules. Graphical abstract Teaser The demands placed on human skin vary by physical location on the body, producing location specificity in cellular composition, signaling pathways, and response to perturbation, including differential susceptibility to inflammation and disease. Quigley et al. show how skin gene networks respond to perturbation by genetic variation, inflammation, and tumorigenesis.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): G. Christopher Tan, Esteban O. Mazzoni, Hynek Wichterle The motor neuron progenitor domain in the ventral spinal cord gives rise to multiple subtypes of motor neurons and glial cells. Here, we examine whether progenitors found in this domain are multipotent and which signals contribute to their cell-type-specific differentiation. Using an in vitro neural differentiation model, we demonstrate that motor neuron progenitor differentiation is iteratively controlled by Notch signaling. First, Notch controls the timing of motor neuron genesis by repressing Neurogenin 2 (Ngn2) and maintaining Olig2-positive progenitors in a proliferative state. Second, in an Ngn2-independent manner, Notch contributes to the specification of median versus hypaxial motor column identity and lateral versus medial divisional identity of limb-innervating motor neurons. Thus, motor neuron progenitors are multipotent, and their diversification is controlled by Notch signaling that iteratively increases cellular diversity arising from a single neural progenitor domain. Graphical abstract Teaser Tan et al. have found an iterative role for Notch signaling during motor neuron differentiation. Notch controls the timing of motor neuron genesis by suppressing Ngn2. Notch is subsequently required in an Ngn2-independent manner for the specification of median motor column identity over hypaxial and lateral motor neuron subtype identities.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Shingo Sato, Yuning J. Tang, Qingxia Wei, Makoto Hirata, Angela Weng, Ilkyu Han, Atsushi Okawa, Shu Takeda, Heather Whetstone, Puvindran Nadesan, David G. Kirsch, Jay S. Wunder, Benjamin A. Alman The cell of origin for most mesenchymal tumors is unclear. One cell type that contributes to this lineages is the pericyte, a cell expressing Ng2/Cspg4 . Using lineage tracing, we demonstrated that bone and soft tissue sarcomas driven by the deletion of the Trp53 tumor suppressor, or desmoid tumors driven by a mutation in Apc , can derive from cells expressing Ng2/Cspg4 . Deletion of the Trp53 tumor suppressor gene in these cells resulted in the bone and soft tissue sarcomas that closely resemble human sarcomas, while stabilizing β-catenin in this same cell type caused desmoid tumors. Comparing expression between Ng2/Cspg4 -expressing pericytes lacking Trp53 and sarcomas that arose from deletion of Trp53 showed inhibition of β-catenin signaling in the sarcomas. Activation of β-catenin inhibited the formation and growth of sarcomas. Thus, pericytes can be a cell of origin for mesenchymal tumors, and β-catenin dysregulation plays an important role in the neoplastic phenotype. Graphical abstract Teaser Sato et al. use lineage-tracing studies in mice to show that bone and soft tissue sarcomas driven by the deletion of the Trp53 tumor suppressor gene can derive from Ng2/Cspg4 -expressing pericytes. Their data show that pericytes can be a cell of origin for mesenchymal tumors and that β-catenin plays a critical role in mesenchymal neoplasia.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Phillip Larimer, Julien Spatazza, Juan Sebastian Espinosa, Yunshuo Tang, Megumi Kaneko, Andrea R. Hasenstaub, Michael P. Stryker, Arturo Alvarez-Buylla The maturation of inhibitory GABAergic cortical circuits regulates experience-dependent plasticity. We recently showed that the heterochronic transplantation of parvalbumin (PV) or somatostatin (SST) interneurons from the medial ganglionic eminence (MGE) reactivates ocular dominance plasticity (ODP) in the postnatal mouse visual cortex. Might other types of interneurons similarly induce cortical plasticity? Here, we establish that caudal ganglionic eminence (CGE)-derived interneurons, when transplanted into the visual cortex of neonatal mice, migrate extensively in the host brain and acquire laminar distribution, marker expression, electrophysiological properties, and visual response properties like those of host CGE interneurons. Although transplants from the anatomical CGE do induce ODP, we found that this plasticity reactivation is mediated by a small fraction of MGE-derived cells contained in the transplant. These findings demonstrate that transplanted CGE cells can successfully engraft into the postnatal mouse brain and confirm the unique role of MGE lineage neurons in the induction of ODP. Graphical abstract Teaser Larimer et al. demonstrate successful transplantation of caudal ganglionic eminence (CGE) neuronal progenitors that differentiate into functional interneurons in the postnatal mouse visual cortex. Although CGE transplants induce ocular dominance plasticity, it is mediated by a small fraction of interneurons derived from the medial ganglionic eminence contained in the transplants.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Matthew S. Stratton, Charles Y. Lin, Priti Anand, Philip D. Tatman, Bradley S. Ferguson, Sean T. Wickers, Amrut V. Ambardekar, Carmen C. Sucharov, James E. Bradner, Saptarsi M. Haldar, Timothy A. McKinsey BRD4 governs pathological cardiac gene expression by binding acetylated chromatin, resulting in enhanced RNA polymerase II (Pol II) phosphorylation and transcription elongation. Here, we describe a signal-dependent mechanism for the regulation of BRD4 in cardiomyocytes. BRD4 expression is suppressed by microRNA-9 (miR-9), which targets the 3′ UTR of the Brd4 transcript. In response to stress stimuli, miR-9 is downregulated, leading to derepression of BRD4 and enrichment of BRD4 at long-range super-enhancers (SEs) associated with pathological cardiac genes. A miR-9 mimic represses stimulus-dependent targeting of BRD4 to SEs and blunts Pol II phosphorylation at proximal transcription start sites, without affecting BRD4 binding to SEs that control constitutively expressed cardiac genes. These findings suggest that dynamic enrichment of BRD4 at SEs genome-wide serves a crucial role in the control of stress-induced cardiac gene expression and define a miR-dependent signaling mechanism for the regulation of chromatin state and Pol II phosphorylation. Graphical abstract Teaser Stratton et al. find that downregulation of microRNA-9 leads to derepression of BRD4 and enrichment of BRD4 at long-range super-enhancers associated with pathological cardiac genes. Dynamic enrichment of BRD4 at super-enhancers serves a crucial role in the control of stress-induced cardiac hypertrophy.

Beschreibung: Publication date: Available online 14 July 2016 Source: Cell Reports Author(s): Nathalie Schmitt, Yang Liu, Salah-Eddine Bentebibel, Hideki Ueno IL-12 is important for the differentiation of T follicular helper (Tfh) cells, as well as Th1 cells in humans. Still, how IL-12 signals regulate Tfh versus Th1 cell differentiation remains poorly characterized. Here we aimed to determine the molecular mechanisms that regulate the differentiation and the function of IL-12-stimulated human naive CD4 + T cells. We found that T-bet promoted the expression of CXCR5 in human CD4 + T cells. We provide evidence that T-bet does not strongly inhibit the Tfh cell differentiation program per se but diminishes the functions to provide help to B cells. This study also suggests that IRF4 plays an important role in driving the early differentiation of IL-12-stimulated CD4 + T cells toward Tfh and away from Th1 by inhibiting the expression of Eomesodermin. Thus, the fate of IL-12-stimulated CD4 + T cells is determined through interplay of multiple transcription factors at early stages. Graphical abstract Teaser Schmitt et al. suggest that Th1 transcription factor T-bet does not strongly inhibit the Tfh cell differentiation program per se but diminishes the helper functions of developing Tfh cells. IRF4 seems important in tipping the balance of Tfh and Th1 differentiation toward Tfh at early stages.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Sungchil Yang, Roy Ben-Shalom, Misol Ahn, Alayna T. Liptak, Richard M. van Rijn, Jennifer L. Whistler, Kevin J. Bender G-protein-coupled receptors (GPCRs) initiate a variety of signaling cascades, depending on effector coupling. β-arrestins, which were initially characterized by their ability to “arrest” GPCR signaling by uncoupling receptor and G protein, have recently emerged as important signaling effectors for GPCRs. β-arrestins engage signaling pathways that are distinct from those mediated by G protein. As such, arrestin-dependent signaling can play a unique role in regulating cell function, but whether neuromodulatory GPCRs utilize β-arrestin-dependent signaling to regulate neuronal excitability remains unclear. Here, we find that D3 dopamine receptors (D3R) regulate axon initial segment (AIS) excitability through β-arrestin-dependent signaling, modifying Ca V 3 voltage dependence to suppress high-frequency action potential generation. This non-canonical D3R signaling thereby gates AIS excitability via pathways distinct from classical GPCR signaling pathways. Graphical abstract Teaser The neuronal site of action potential initiation, the axon initial segment (AIS), has recently gained recognition as a site of neuromodulation and plasticity. Here, Yang et al. demonstrate that D3 dopamine receptors regulate AIS Ca V 3 channels through a non-canonical, arrestin-dependent mechanism, suppressing AIS excitability by hyperpolarizing Ca V 3 voltage-dependent inactivation.

Beschreibung: Publication date: Available online 21 July 2016 Source: Cell Reports Author(s): Matthew Locke, Essam Ghazaly, Marta O. Freitas, Mikaella Mitsinga, Laura Lattanzio, Cristiana Lo Nigro, Ai Nagano, Jun Wang, Claude Chelala, Peter Szlosarek, Sarah A. Martin Argininosuccinate synthase 1 (ASS1) is the rate-limiting enzyme for arginine biosynthesis. ASS1 expression is lost in a range of tumor types, including 50% of malignant pleural mesotheliomas. Starving ASS1-deficient cells of arginine with arginine blockers such as ADI-PEG20 can induce selective lethality and has shown great promise in the clinical setting. We have generated a model of ADI-PEG20 resistance in mesothelioma cells. This resistance is mediated through re-expression of ASS1 via demethylation of the ASS1 promoter. Through coordinated transcriptomic and metabolomic profiling, we have shown that ASS1-deficient cells have decreased levels of acetylated polyamine metabolites, together with a compensatory increase in the expression of polyamine biosynthetic enzymes. Upon arginine deprivation, polyamine metabolites are decreased in the ASS1-deficient cells and in plasma isolated from ASS1-deficient mesothelioma patients. We identify a synthetic lethal dependence between ASS1 deficiency and polyamine metabolism, which could potentially be exploited for the treatment of ASS1-negative cancers. Graphical abstract Teaser Locke et al. have generated a model of ADI-PEG20 resistance in mesothelioma cells. They reveal that ASS1-deficient cells have decreased levels of acetylated polyamine metabolites, together with a compensatory increase in expression of polyamine biosynthetic enzymes. This elucidates a synthetic lethal interaction between ASS1 loss and inhibition of polyamine metabolism.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Rodrigo Lombraña, Alba Álvarez, José Miguel Fernández-Justel, Ricardo Almeida, César Poza-Carrión, Fábia Gomes, Arturo Calzada, José María Requena, María Gómez Faithful inheritance of eukaryotic genomes requires the orchestrated activation of multiple DNA replication origins (ORIs). Although origin firing is mechanistically conserved, how origins are specified and selected for activation varies across different model systems. Here, we provide a complete analysis of the nucleosomal landscape and replication program of the human parasite Leishmania major , building on a better evolutionary understanding of replication organization in Eukarya. We found that active transcription is a driving force for the nucleosomal organization of the L. major genome and that both the spatial and the temporal program of DNA replication can be explained as associated to RNA polymerase kinetics. This simple scenario likely provides flexibility and robustness to deal with the environmental changes that impose alterations in the genetic programs during parasitic life cycle stages. Our findings also suggest that coupling replication initiation to transcription elongation could be an ancient solution used by eukaryotic cells for origin maintenance. Graphical abstract Teaser Though the mechanism of DNA replication origin activation is well understood and conserved among eukaryotes, the determinants of origin specification seem to vary across different model systems. Lombraña et al. found that active transcription is the primary determinant underlying the temporal and spatial replication of the Leishmania major genome.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Yoanne M. Clovis, So Yeon Seo, Ji-sun Kwon, Jennifer C. Rhee, Sujeong Yeo, Jae W. Lee, Seunghee Lee, Soo-Kyung Lee During development, two cell types born from closely related progenitor pools often express identical transcriptional regulators despite their completely distinct characteristics. This phenomenon implies the need for a mechanism that operates to segregate the identities of the two cell types throughout differentiation after initial fate commitment. To understand this mechanism, we investigated the fate specification of spinal V2a interneurons, which share important developmental genes with motor neurons (MNs). We demonstrate that the paired homeodomain factor Chx10 functions as a critical determinant for V2a fate and is required to consolidate V2a identity in postmitotic neurons. Chx10 actively promotes V2a fate, downstream of the LIM-homeodomain factor Lhx3, while concomitantly suppressing the MN developmental program by preventing the MN-specific transcription complex from binding and activating MN genes. This dual activity enables Chx10 to effectively separate the V2a and MN pathways. Our study uncovers a widely applicable gene regulatory principle for segregating related cell fates. Graphical abstract Teaser Clovis et al. describe the mechanism through which spinal V2a interneurons are specified. They find that the best-known marker for V2a interneurons, Chx10, is the major determinant of V2a fate specification. Chx10 upregulates the expression of V2a interneuron genes while suppressing the expression of non-V2a interneuron and motor neuron genes.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Frédéric Pontvianne, Marie-Christine Carpentier, Nathalie Durut, Veronika Pavlištová, Karin Jaške, Šárka Schořová, Hugues Parrinello, Marine Rohmer, Craig S. Pikaard, Miloslava Fojtová, Jiří Fajkus, Julio Sáez-Vásquez The nucleolus is the site of rRNA gene transcription, rRNA processing, and ribosome biogenesis. However, the nucleolus also plays additional roles in the cell. We isolated nucleoli using fluorescence-activated cell sorting (FACS) and identified nucleolus-associated chromatin domains (NADs) by deep sequencing, comparing wild-type plants and null mutants for the nucleolar protein NUCLEOLIN 1 (NUC1). NADs are primarily genomic regions with heterochromatic signatures and include transposable elements (TEs), sub-telomeric regions, and mostly inactive protein-coding genes. However, NADs also include active rRNA genes and the entire short arm of chromosome 4 adjacent to them. In nuc1 null mutants, which alter rRNA gene expression and overall nucleolar structure, NADs are altered, telomere association with the nucleolus is decreased, and telomeres become shorter. Collectively, our studies reveal roles for NUC1 and the nucleolus in the spatial organization of chromosomes as well as telomere maintenance. Graphical abstract Teaser To evaluate the effect of the nucleolus in plant genome organization, Pontvianne et al. identify nucleolus-associated chromatin domains (NADs) in A. thaliana leaves. NADs are enriched in regions displaying heterochromatic signatures. We find roles for Nucleolin 1 (NUC1) and the nucleolus in the spatial organization of chromosomes and also in telomere maintenance.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Nicole K. Littlejohn, Henry L. Keen, Benjamin J. Weidemann, Kristin E. Claflin, Kevin V. Tobin, Kathleen R. Markan, Sungmi Park, Meghan C. Naber, Francoise A. Gourronc, Nicole A. Pearson, Xuebo Liu, Donald A. Morgan, Aloysius J. Klingelhutz, Matthew J. Potthoff, Kamal Rahmouni, Curt D. Sigmund, Justin L. Grobe Activation of the brain renin-angiotensin system (RAS) stimulates energy expenditure through increasing of the resting metabolic rate (RMR), and this effect requires simultaneous suppression of the circulating and/or adipose RAS. To identify the mechanism by which the peripheral RAS opposes RMR control by the brain RAS, we examined mice with transgenic activation of the brain RAS (sRA mice). sRA mice exhibit increased RMR through increased energy flux in the inguinal adipose tissue, and this effect is attenuated by angiotensin II type 2 receptor (AT 2 ) activation. AT 2 activation in inguinal adipocytes opposes norepinephrine-induced uncoupling protein-1 (UCP1) production and aspects of cellular respiration, but not lipolysis. AT 2 activation also opposes inguinal adipocyte function and differentiation responses to epidermal growth factor (EGF). These results highlight a major, multifaceted role for AT 2 within inguinal adipocytes in the control of RMR. The AT 2 receptor may therefore contribute to body fat distribution and adipose depot-specific effects upon cardio-metabolic health. Graphical abstract Teaser The renin-angiotensin system has been implicated in tissue-specific actions underlying energy balance physiology. Littlejohn et al. document a major role for the angiotensin AT 2 receptor in the regulation of resting metabolism, through the control of differentiation and thermogenic capacity of subcutaneous adipocytes.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Mee-Sup Yoon, Kook Son, Edwin Arauz, Jung Min Han, Sunghoon Kim, Jie Chen Amino acid availability activates signaling by the mammalian target of rapamycin (mTOR) complex 1, mTORC1, a master regulator of cell growth. The class III PI-3-kinase Vps34 mediates amino acid signaling to mTORC1 by regulating lysosomal translocation and activation of the phospholipase PLD1. Here, we identify leucyl-tRNA synthetase (LRS) as a leucine sensor for the activation of Vps34-PLD1 upstream of mTORC1. LRS is necessary for amino acid-induced Vps34 activation, cellular PI(3)P level increase, PLD1 activation, and PLD1 lysosomal translocation. Leucine binding, but not tRNA charging activity of LRS, is required for this regulation. Moreover, LRS physically interacts with Vps34 in amino acid-stimulatable non-autophagic complexes. Finally, purified LRS protein activates Vps34 kinase in vitro in a leucine-dependent manner. Collectively, our findings provide compelling evidence for a direct role of LRS in amino acid activation of Vps34 via a non-canonical mechanism and fill a gap in the amino acid-sensing mTORC1 signaling network. Graphical abstract Teaser Yoon et al. identify leucyl-tRNA synthetase (LRS) as a leucine sensor that directly activates the lipid kinase Vps34 and mediates amino acid activation of a Vps34-PLD1-mTORC1 pathway. Their findings reveal a non-canonical function for LRS and fill a previous gap in the amino acid-sensing mTORC1 signaling network.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Xun Jin, Hye-Min Jeon, Xiong Jin, Eun-Jung Kim, Jinlong Yin, Hee-Young Jeon, Young-Woo Sohn, Se-Yeong Oh, Jun-Kyum Kim, Sung-Hak Kim, Ji-Eun Jung, Sungwook Kwak, Kai-Fu Tang, Yunsheng Xu, Jeremy N. Rich, Hyunggee Kim Inhibitor of differentiation 1 (ID1) is highly expressed in glioblastoma stem cells (GSCs). However, the regulatory mechanism responsible for its role in GSCs is poorly understood. Here, we report that ID1 activates GSC proliferation, self-renewal, and tumorigenicity by suppressing CULLIN3 ubiquitin ligase. ID1 induces cell proliferation through increase of CYCLIN E, a target molecule of CULLIN3. ID1 overexpression or CULLIN3 knockdown confers GSC features and tumorigenicity to murine Ink4a/Arf -deficient astrocytes. Proteomics analysis revealed that CULLIN3 interacts with GLI2 and DVL2 and induces their degradation via ubiquitination. Consistent with ID1 knockdown or CULLIN3 overexpression in human GSCs, pharmacologically combined control of GLI2 and β-CATENIN effectively diminishes GSC properties. A ID1-high/CULLIN3-low expression signature correlates with a poor patient prognosis, supporting the clinical relevance of this signaling axis. Taken together, a loss of CULLIN3 represents a common signaling node for controlling the activity of intracellular WNT and SHH signaling pathways mediated by ID1. Graphical abstract Teaser Jin et al. report that the deregulated proteolysis by ID1-mediated suppression of CULLIN3 controls glioblastoma stem cell proliferation, self-renewal, and tumorigenicity by simultaneously activating intracellular WNT and SHH signaling. The findings provide a rationale for therapeutic intervention targeting multiple intracellular cancer stemness signaling pathways.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Jonathan Maelfait, Anne Bridgeman, Adel Benlahrech, Chiara Cursi, Jan Rehwinkel SAMHD1 is a restriction factor for HIV-1 infection. SAMHD1 mutations cause the autoinflammatory Aicardi-Goutières syndrome that is characterized by chronic type I interferon (IFN) secretion. We show that the spontaneous IFN response in SAMHD1-deficient cells and mice requires the cGAS/STING cytosolic DNA-sensing pathway. We provide genetic evidence that cell-autonomous control of lentivirus infection in myeloid cells by SAMHD1 limits virus-induced production of IFNs and the induction of co-stimulatory markers. This program of myeloid cell activation required reverse transcription, cGAS and STING, and signaling through the IFN receptor. Furthermore, SAMHD1 reduced the induction of virus-specific cytotoxic T cells in vivo. Therefore, virus restriction by SAMHD1 limits the magnitude of IFN and T cell responses. This demonstrates a competition between cell-autonomous virus control and subsequent innate and adaptive immune responses, a concept with important implications for the treatment of infection. Graphical abstract Teaser Restriction factors defend infected cells against viruses. Maelfait et al. find that SAMHD1, which blocks HIV-1 infection in myeloid cells, prevents innate sensing of infection via cGAS/STING. Furthermore, SAMHD1 curtails virus-specific T cell responses in vivo. Restriction by SAMHD1, therefore, limits subsequent innate and adaptive immune responses.

Beschreibung: Publication date: Available online 28 July 2016 Source: Cell Reports Author(s): Peng Ru, Peng Hu, Feng Geng, Xiaokui Mo, Chunming Cheng, Ji Young Yoo, Xiang Cheng, Xiaoning Wu, Jeffrey Yunhua Guo, Ichiro Nakano, Etienne Lefai, Balveen Kaur, Arnab Chakravarti, Deliang Guo Dysregulated lipid metabolism is a characteristic of malignancies. Sterol regulatory element binding protein 1 (SREBP-1), a transcription factor playing a central role in lipid metabolism, is highly activated in malignancies. Here, we unraveled a link between miR-29 and the SCAP (SREBP cleavage-activating protein)/SREBP-1 pathway in glioblastoma (GBM) growth. Epidermal growth factor receptor (EGFR) signaling enhances miR-29 expression in GBM cells via upregulation of SCAP/SREBP-1, and SREBP-1 activates miR-29 expression via binding to specific sites in its promoter. In turn, miR-29 inhibits SCAP and SREBP-1 expression by interacting with their 3′ UTRs. miR-29 transfection suppressed lipid synthesis and GBM cell growth, which were rescued by the addition of fatty acids or N-terminal SREBP-1 expression. Xenograft studies showed that miR-29 mimics significantly inhibit GBM growth and prolong the survival of GBM-bearing mice. Our study reveals a previously unrecognized negative feedback loop in SCAP/SREBP-1 signaling mediated by miR-29 and suggests that miR-29 treatment may represent an effective means to target GBM. Graphical abstract Teaser In this study, Ru et al. unravel a negative feedback loop mediated by miR-29 in SCAP/SREBP-1 signaling, advancing our understanding of lipid metabolism. The study also indicates that miR-29-mediated inhibition of SCAP/SREBP-1 may be a promising approach for targeting glioblastoma.