ALBERT

Description: Publication date: Available online 20 August 2015 Source: Cell Reports Author(s): Bettina Schreiner, Elisa Romanelli, Pawel Liberski, Barbara Ingold-Heppner, Bettina Sobottka-Brillout, Tom Hartwig, Vijay Chandrasekar, Helge Johannssen, Hanns Ulrich Zeilhofer, Adriano Aguzzi, Frank Heppner, Martin Kerschensteiner, Burkhard Becher Although the importance of reactive astrocytes during CNS pathology is well established, the function of astroglia in adult CNS homeostasis is less well understood. With the use of conditional, astrocyte-restricted protein synthesis termination, we found that selective paralysis of GFAP + astrocytes in vivo led to rapid neuronal cell loss and severe motor deficits. This occurred while structural astroglial support still persisted and in the absence of any major microvascular damage. Whereas loss of astrocyte function did lead to microglial activation, this had no impact on the neuronal loss and clinical decline. Neuronal injury was caused by oxidative stress resulting from the reduced redox scavenging capability of dysfunctional astrocytes and could be prevented by the in vivo treatment with scavengers of reactive oxygen and nitrogen species (ROS/RNS). Our results suggest that the subpopulation of GFAP + astrocytes maintain neuronal health by controlling redox homeostasis in the adult CNS. Graphical abstract Teaser Schreiner et al. examine the functional contribution of astrocytes to tissue homeostasis in the adult CNS and identify the redox-scavenging capacity of GFAP + astrocytes as a key factor for neuronal health in vivo. The importance of the metabolic integrity of the glia-neuron interface highlights potential therapies for the treatment of neurodegenerative diseases.

Description: Publication date: Available online 20 August 2015 Source: Cell Reports Author(s): Priya Srikanth, Karam Han, Dana G. Callahan, Eugenia Makovkina, Christina R. Muratore, Matthew A. Lalli, Honglin Zhou, Justin D. Boyd, Kenneth S. Kosik, Dennis J. Selkoe, Tracy L. Young-Pearse Genetic and clinical association studies have identified disrupted in schizophrenia 1 ( DISC1 ) as a candidate risk gene for major mental illness. DISC1 is interrupted by a balanced chr(1;11) translocation in a Scottish family in which the translocation predisposes to psychiatric disorders. We investigate the consequences of DISC1 interruption in human neural cells using TALENs or CRISPR-Cas9 to target the DISC1 locus. We show that disruption of DISC1 near the site of the translocation results in decreased DISC1 protein levels because of nonsense-mediated decay of long splice variants. This results in an increased level of canonical Wnt signaling in neural progenitor cells and altered expression of fate markers such as Foxg1 and Tbr2. These gene expression changes are rescued by antagonizing Wnt signaling in a critical developmental window, supporting the hypothesis that DISC1-dependent suppression of basal Wnt signaling influences the distribution of cell types generated during cortical development. Graphical abstract Teaser Srikanth et al. report the generation of isogenic hiPSC lines with engineered mutations in two locations within the DISC1 gene. This disease-relevant disruption shows a loss of long isoforms, which, in turn, affects neural progenitor cell proliferation, baseline WNT signaling, and the expression of NPC fate markers such as FoxG1 and Tbr2.

Description: Publication date: Available online 20 August 2015 Source: Cell Reports Author(s): Ivana Vonkova, Antoine-Emmanuel Saliba, Samy Deghou, Kanchan Anand, Stefano Ceschia, Tobias Doerks, Augustinus Galih, Karl G. Kugler, Kenji Maeda, Vladimir Rybin, Vera van Noort, Jan Ellenberg, Peer Bork, Anne-Claude Gavin Many cellular processes involve the recruitment of proteins to specific membranes, which are decorated with distinctive lipids that act as docking sites. The phosphoinositides form signaling hubs, and we examine mechanisms underlying recruitment. We applied a physiological, quantitative, liposome microarray-based assay to measure the membrane-binding properties of 91 pleckstrin homology (PH) domains, the most common phosphoinositide-binding target. 10,514 experiments quantified the role of phosphoinositides in membrane recruitment. For most domains examined, the observed binding specificity implied cooperativity with additional signaling lipids. Analyses of PH domains with similar lipid-binding profiles identified a conserved motif, mutations in which—including some found in human cancers—induced discrete changes in binding affinities in vitro and protein mislocalization in vivo. The data set reveals cooperativity as a key mechanism for membrane recruitment and, by enabling the interpretation of disease-associated mutations, suggests avenues for the design of small molecules targeting PH domains. Graphical abstract Teaser Vonkova et al. systematically quantify the lipid-binding properties of 91 pleckstrin homology (PH) domains using a physiological, quantitative, liposome microarray-based assay. The data set reveals that cooperativity between lipids is a key mechanism for membrane recruitment of PH domains.

Description: Publication date: Available online 20 August 2015 Source: Cell Reports Author(s): Ju-Hyun Lee, Mary Kate McBrayer, Devin M. Wolfe, Luke J. Haslett, Asok Kumar, Yutaka Sato, Pearl P.Y. Lie, Panaiyur Mohan, Erin E. Coffey, Uday Kompella, Claire H. Mitchell, Emyr Lloyd-Evans, Ralph A. Nixon Presenilin 1 (PS1) deletion or Alzheimer’s disease (AD)-linked mutations disrupt lysosomal acidification and proteolysis, which inhibits autophagy. Here, we establish that this phenotype stems from impaired glycosylation and instability of vATPase V0a1 subunit, causing deficient lysosomal vATPase assembly and function. We further demonstrate that elevated lysosomal pH in Presenilin 1 knockout (PS1KO) cells induces abnormal Ca 2+ efflux from lysosomes mediated by TRPML1 and elevates cytosolic Ca 2+ . In WT cells, blocking vATPase activity or knockdown of either PS1 or the V0a1 subunit of vATPase reproduces all of these abnormalities. Normalizing lysosomal pH in PS1KO cells using acidic nanoparticles restores normal lysosomal proteolysis, autophagy, and Ca 2+ homeostasis, but correcting lysosomal Ca 2+ deficits alone neither re-acidifies lysosomes nor reverses proteolytic and autophagic deficits. Our results indicate that vATPase deficiency in PS1 loss-of-function states causes lysosomal/autophagy deficits and contributes to abnormal cellular Ca 2+ homeostasis, thus linking two AD-related pathogenic processes through a common molecular mechanism. Graphical abstract Teaser Lee et al. present evidence establishing that Presenilin 1 loss of function elevates lysosomal pH via loss of V0a1 vATPase subunits. Besides disrupting autophagy, elevated lysosomal pH hyperactivates the TRPML1 calcium channel, causing increased lysosomal calcium efflux and cytosolic calcium elevation, thus linking two AD-related presenilin phenotypes to vATPase deficiency.

Description: Publication date: Available online 20 August 2015 Source: Cell Reports Author(s): Soraia Barão, Annette Gärtner, Eduardo Leyva-Díaz, Galina Demyanenko, Sebastian Munck, Tine Vanhoutvin, Lujia Zhou, Melitta Schachner, Guillermina López-Bendito, Patricia F. Maness, Bart De Strooper ΒACE1 is the major drug target for Alzheimer’s disease, but we know surprisingly little about its normal function in the CNS. Here, we show that this protease is critically involved in semaphorin 3A (Sema3A)-mediated axonal guidance processes in thalamic and hippocampal neurons. An active membrane-bound proteolytic CHL1 fragment is generated by BACE1 upon Sema3A binding. This fragment relays the Sema3A signal via ezrin-radixin-moesin (ERM) proteins to the neuronal cytoskeleton. APH1B-γ-secretase-mediated degradation of this fragment stops the Sema3A-induced collapse and sensitizes the growth cone for the next axonal guidance cue. Thus, we reveal a cycle of proteolytic activity underlying growth cone collapse and restoration used by axons to find their correct trajectory in the brain. Our data also suggest that BACE1 and γ-secretase inhibition have physiologically opposite effects in this process, supporting the idea that combination therapy might attenuate some of the side effects associated with these drugs. Graphical abstract Teaser Barão et al. show that the Alzheimer’s-disease-related proteases, BACE1 and APH1B-γ-secretase, control axonal guidance by regulating growth cone dynamics. BACE1 cleaves CHL1, inducing growth cone collapse. Subsequently, γ-secretase activity stops the collapse and axonal growth resumes. Therefore, testing of inhibitors of these proteases in humans should proceed with caution.

Description: Publication date: Available online 20 August 2015 Source: Cell Reports Author(s): Alexander Harms, Frédéric Valentin Stanger, Patrick Daniel Scheu, Imke Greet de Jong, Arnaud Goepfert, Timo Glatter, Kenn Gerdes, Tilman Schirmer, Christoph Dehio Toxin-antitoxin (TA) modules are ubiquitous molecular switches controlling bacterial growth via the release of toxins that inhibit cell proliferation. Most of these toxins interfere with protein translation, but a growing variety of other mechanisms hints at a diversity that is not yet fully appreciated. Here, we characterize a group of FIC domain proteins as toxins of the conserved and abundant FicTA family of TA modules, and we reveal that they act by suspending control of cellular DNA topology. We show that FicTs are enzymes that adenylylate DNA gyrase and topoisomerase IV, the essential bacterial type IIA topoisomerases, at their ATP-binding site. This modification inactivates both targets by blocking their ATPase activity, and, consequently, causes reversible growth arrest due to the knotting, catenation, and relaxation of cellular DNA. Our results give insight into the regulation of DNA topology and highlight the remarkable plasticity of FIC domain proteins. Graphical abstract Teaser Harms et al. reveal that the FicTA toxin-antitoxin module acts via adenylylation of DNA gyrase and topoisomerase IV. This modification inactivates both targets by blocking the ATPase activity that is central to their enzymatic functions, and it reversibly inhibits bacterial growth via the knotting, catenation, and relaxation of cellular DNA.

Description: Publication date: Available online 20 August 2015 Source: Cell Reports Author(s): Takaharu Kanno, Davide G. Berta, Camilla Sjögren The structural maintenance of chromosome (SMC) protein complexes cohesin and condensin and the Smc5/6 complex (Smc5/6) are crucial for chromosome dynamics and stability. All contain essential ATPase domains, and cohesin and condensin interact with chromosomes through topological entrapment of DNA. However, how Smc5/6 binds DNA and chromosomes has remained largely unknown. Here, we show that purified Smc5/6 binds DNA through a mechanism that requires ATP hydrolysis by the complex and circular DNA to be established. This also promotes topoisomerase 2-dependent catenation of plasmids, suggesting that Smc5/6 interconnects two DNA molecules using ATP-regulated topological entrapment of DNA, similar to cohesin. We also show that a complex containing an Smc6 mutant that is defective in ATP binding fails to interact with DNA and chromosomes and leads to cell death with concomitant accumulation of DNA damage when overexpressed. Taken together, these results indicate that Smc5/6 executes its cellular functions through ATP-regulated intermolecular DNA linking. Graphical abstract Teaser Kanno et al. have found that Smc5/6 interacts with DNA by two different mechanisms. One is based on electrostatic interactions that require ATP binding to Smc6. The other leads to topological entrapment and demands ATP hydrolysis by the complex. The results show that Smc5/6 is an ATP-dependent intermolecular DNA linker.

Description: Publication date: 18 August 2015 Source: Cell Reports, Volume 12, Issue 7 Author(s): Marvin L. Meistrich, Gunapala Shetty In this issue of Cell Reports , DeFalco et al. (2015) characterize a novel macrophage population associated with the peritubular lamina of mouse testes. These macrophages may create a niche not for the self-renewal of stem cells but rather the induction of their differentiation.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Kavita R. Sharma, Brittany L. Enzmann, Yvonne Schmidt, Dani Moore, Graeme R. Jones, Jane Parker, Shelley L. Berger, Danny Reinberg, Laurence J. Zwiebel, Bernhard Breit, Jürgen Liebig, Anandasankar Ray The sophisticated organization of eusocial insect societies is largely based on the regulation of complex behaviors by hydrocarbon pheromones present on the cuticle. We used electrophysiology to investigate the detection of cuticular hydrocarbons (CHCs) by female-specific olfactory sensilla basiconica on the antenna of Camponotus floridanus ants through the utilization of one of the largest family of odorant receptors characterized so far in insects. These sensilla, each of which contains multiple olfactory receptor neurons, are differentially sensitive to CHCs and allow them to be classified into three broad groups that collectively detect every hydrocarbon tested, including queen and worker-enriched CHCs. This broad-spectrum sensitivity is conserved in a related species, Camponotus laevigatus , allowing these ants to detect CHCs from both nestmates and non-nestmates. Behavioral assays demonstrate that these ants are excellent at discriminating CHCs detected by the antenna, including enantiomers of a candidate queen pheromone that regulates the reproductive division of labor. Graphical abstract Teaser Sharma et al. show that ants can detect a number of hydrocarbons present on the cuticle, therefore recognizing different castes such as workers and queens from their own colony as well as different colonies. They also show that ants are able to smell and discriminate minor differences among hydrocarbons.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Sanjeev Kumar, Jing Liu, Paul Pang, A. Michaela Krautzberger, Antoine Reginensi, Haruhiko Akiyama, Andreas Schedl, Benjamin D. Humphreys, Andrew P. McMahon After acute kidney injury (AKI), surviving cells within the nephron proliferate and repair. We identify Sox9 as an acute epithelial stress response in renal regeneration. Translational profiling after AKI revealed a rapid upregulation of Sox9 within proximal tubule (PT) cells, the nephron cell type most vulnerable to AKI. Descendants of Sox9 + cells generate the bulk of the nephron during development and regenerate functional PT epithelium after AKI-induced reactivation of Sox9 after renal injury. After restoration of renal function post-AKI, persistent Sox9 expression highlights regions of unresolved damage within injured nephrons. Inactivation of Sox9 in PT cells pre-injury indicates that Sox9 is required for the normal course of post-AKI recovery. These findings link Sox9 to cell intrinsic mechanisms regulating development and repair of the mammalian nephron. Graphical abstract Teaser Surviving tubular epithelial cells repair the nephron after acute kidney injury (AKI). Kumar et al. identify Sox9 activation as a rapid response to AKI within repairing cells of the damaged proximal tubule segment. Sox9 activation is required for a normal repair process.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Rheinallt M. Jones, Chirayu Desai, Trevor M. Darby, Liping Luo, Alexandra A. Wolfarth, Christopher D. Scharer, Courtney S. Ardita, April R. Reedy, Erin S. Keebaugh, Andrew S. Neish An optimal gut microbiota influences many beneficial processes in the metazoan host. However, the molecular mechanisms that mediate and function in symbiont-induced host responses have not yet been fully characterized. Here, we report that cellular ROS enzymatically generated in response to contact with lactobacilli in both mice and Drosophila has salutary effects against exogenous insults to the intestinal epithelium via the activation of Nrf2 responsive cytoprotective genes. These data show that the xenobiotic-inducible Nrf2 pathway participates as a signaling conduit between the prokaryotic symbiont and the eukaryotic host. Indeed, our data imply that the capacity of lactobacilli to induce redox signaling in epithelial cells is a highly conserved hormetic adaptation to impel cellular conditioning to exogenous biotic stimuli. These data also highlight the role the microbiota plays in eukaryotic cytoprotective pathways and may have significant implications in the characterization of a eubiotic microbiota. Graphical abstract Teaser Jones et al. report that the commensal gut bacterial taxa lactobacilli are able to mediate beneficial cytoprotective effects in the gut of both flies and mice. These highly conserved events are mediated by ROS-dependent activation of the Nrf2 xenobiotic pathway and conserved effector genes.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Neel Mehta, Arthur H. Cheng, Cheng-Kang Chiang, Lucia Mendoza-Viveros, Harrod H. Ling, Abhilasha Patel, Bo Xu, Daniel Figeys, Hai-Ying M. Cheng The pacemaker properties of the suprachiasmatic nucleus (SCN) circadian clock are shaped by mechanisms that influence the expression and behavior of clock proteins. Here, we reveal that G-protein-coupled receptor kinase 2 (GRK2) modulates the period, amplitude, and entrainment characteristics of the SCN. Grk2 -deficient mice show phase-dependent alterations in light-induced entrainment, slower recovery from jetlag, and longer behavioral rhythms. Grk2 ablation perturbs intrinsic rhythmic properties of the SCN, increasing amplitude and decreasing period. At the cellular level, GRK2 suppresses the transcription of the mPeriod1 gene and the trafficking of PERIOD1 and PERIOD2 proteins to the nucleus. Moreover, GRK2 can physically interact with PERIOD1/2 and promote PERIOD2 phosphorylation at Ser545, effects that may underlie its ability to regulate PERIOD1/2 trafficking. Together, our findings identify GRK2 as an important modulator of circadian clock speed, amplitude, and entrainment by controlling PERIOD at the transcriptional and post-translational levels. Graphical abstract Teaser Mehta et al. demonstrate the importance of GRK2 in regulating both the pace of the circadian clock and its response to environmental time cues (i.e., light). GRK2 functionally interacts with the molecular clock at the transcriptional and post-translational levels, dampening mPeriod1 gene transcription and suppressing nuclear trafficking of PERIOD1/2 proteins.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Juan F. Linares, Angeles Duran, Miguel Reina-Campos, Pedro Aza-Blanc, Alex Campos, Jorge Moscat, Maria T. Diaz-Meco The mTORC1 complex is central to the cellular response to changes in nutrient availability. The signaling adaptor p62 contributes to mTORC1 activation in response to amino acids and interacts with TRAF6, which is required for the translocation of mTORC1 to the lysosome and the subsequent K63 polyubiquitination and activation of mTOR. However, the signal initiating these p62-driven processes was previously unknown. Here, we show that p62 is phosphorylated via a cascade that includes MEK3/6 and p38δ and is driven by the PB1-containing kinase MEKK3. This phosphorylation results in the recruitment of TRAF6 to p62, the ubiquitination and activation of mTOR, and the regulation of autophagy and cell proliferation. Genetic inactivation of MEKK3 or p38δ mimics that of p62 in that it leads to inhibited growth of PTEN-deficient prostate organoids. Analysis of human prostate cancer samples showed upregulation of these three components of the pathway, which correlated with enhanced mTORC1 activation. Graphical abstract Teaser Linares et al. identify a kinase cascade that regulates the phosphorylation of the signal adaptor p62 in response to amino acids to control mTORC1 activation. This nutrient-sensing mechanism is relevant for autophagy regulation and tumor growth.

Description: Publication date: 4 August 2015 Source: Cell Reports, Volume 12, Issue 5 Author(s): Obinna Chijioke, Anne Müller, Regina Feederle, Mario Henrique M. Barros, Carsten Krieg, Vanessa Emmel, Emanuela Marcenaro, Carol S. Leung, Olga Antsiferova, Vanessa Landtwing, Walter Bossart, Alessandro Moretta, Rocio Hassan, Onur Boyman, Gerald Niedobitek, Henri-Jacques Delecluse, Riccarda Capaul, Christian Münz

Description: Publication date: Available online 6 August 2015 Source: Cell Reports Author(s): Matthew T. Maurano, Hao Wang, Sam John, Anthony Shafer, Theresa Canfield, Kristen Lee, John A. Stamatoyannopoulos Although DNA methylation is commonly invoked as a mechanism for transcriptional repression, the extent to which it actively silences transcription factor (TF) occupancy sites in vivo is unknown. To study the role of DNA methylation in the active modulation of TF binding, we quantified the effect of DNA methylation depletion on the genomic occupancy patterns of CTCF, an abundant TF with known methylation sensitivity that is capable of autonomous binding to its target sites in chromatin. Here, we show that the vast majority (>98.5%) of the tens of thousands of unoccupied, methylated CTCF recognition sequences remain unbound upon abrogation of DNA methylation. The small fraction of sites that show methylation-dependent binding in vivo are in turn characterized by highly variable CTCF occupancy across cell types. Our results suggest that DNA methylation is not a primary groundskeeper of genomic TF landscapes, but rather a specialized mechanism for stabilizing intrinsically labile sites. Graphical abstract Teaser Alterations of DNA methylation in malignancy and development are frequently interpreted as affecting transcriptional activity. Maurano et al. find that, upon genomic abrogation of DNA methylation, binding of the canonically methylation-sensitive transcriptional regulator CTCF is largely unaffected. Their results suggest that a limited set of methylation-sensitive CTCF sites are variable across cell types and that key sequence and chromatin features predict methylation sensitivity of CTCF binding.

Description: Publication date: Available online 6 August 2015 Source: Cell Reports Author(s): Swea-Ling Khaw, Chua Min-Wen, Cheng-Gee Koh, Bing Lim, Ng Shyh-Chang Oocyte factors not only drive somatic cell nuclear transfer reprogramming but also augment the efficiency and quality of induced pluripotent stem cell (iPSC) reprogramming. Here, we show that the oocyte-enriched factors Tcl1 and Tcl1b1 significantly enhance reprogramming efficiency. Clonal analysis of pluripotency biomarkers further show that the Tcl1 oocyte factors improve the quality of reprogramming. Mechanistically, we find that the enhancement effect of Tcl1b1 depends on Akt, one of its putative targets. In contrast, Tcl1 suppresses the mitochondrial polynucleotide phosphorylase (PnPase) to promote reprogramming. Knockdown of PnPase rescues the inhibitory effect from Tcl1 knockdown during reprogramming, whereas PnPase overexpression abrogates the enhancement from Tcl1 overexpression. We further demonstrate that Tcl1 suppresses PnPase’s mitochondrial localization to inhibit mitochondrial biogenesis and oxidation phosphorylation, thus remodeling the metabolome. Hence, we identified the Tcl1-PnPase pathway as a critical mitochondrial switch during reprogramming. Graphical abstract Teaser Khaw et al. identify the oocyte Tcl1-PnPase pathway as a critical mitochondrial switch during reprogramming into iPSCs. They find that Tcl1 suppresses the mitochondrial localization of PNPase, thus inhibiting mitochondrial biogenesis and oxidation phosphorylation.

Description: Publication date: Available online 6 August 2015 Source: Cell Reports Author(s): Xinfang Huang, Jingjing Li, Stephanie Dorta-Estremera, Jeremy Di Domizio, Scott M. Anthony, Stephanie S. Watowich, Daniel Popkin, Zheng Liu, Philip Brohawn, Yihong Yao, Kimberly S. Schluns, Lewis L. Lanier, Wei Cao Here, we examine the mechanism by which plasmacytoid dendritic cells (pDCs) and type I interferons promote humoral autoimmunity. In an amyloid-induced experimental autoimmune model, neutrophil depletion enhanced anti-nuclear antibody development, which correlated with heightened IFN-γ production by natural killer (NK) cells. IFN-α/β produced by pDCs activated NK cells via IL-15 induction. Neutrophils released reactive oxygen species (ROS), which negatively modulated the levels of IL-15, thereby inhibiting IFN-γ production. Mice deficient in NADPH oxidase 2 produced increased amounts of IFN-γ and developed augmented titers of autoantibodies. Both the pDC-IFN-α/β pathway and IFN-γ were indispensable in stimulating humoral autoimmunity. Male NZB/W F1 mice expressed higher levels of superoxide than their female lupus-prone siblings, and depletion of neutrophils resulted in spontaneous NK cell and autoimmune B cell activation. Our findings suggest a regulatory role for neutrophils in vivo and highlight the importance of an NK-IFN-γ axis downstream of the pDC-IFN-α/β pathway in systemic autoimmunity. Graphical abstract Teaser Huang et al. find that IFN-α/β produced by plasmacytoid dendritic cells (pDCs) stimulates NK cells to secrete IFN-γ, which is essential for the development of autoantibodies. ROS-producing neutrophils negatively regulate this NK-IFN-γ pathway and control autoimmune progression in lupus-prone mice.

Description: Publication date: Available online 4 June 2015 Source: Cell Reports Author(s): Laura W. Dillon , Pankaj Kumar , Yoshiyuki Shibata , Yuh-Hwa Wang , Smaranda Willcox , Jack D. Griffith , Yves Pommier , Shunichi Takeda , Anindya Dutta MicroDNAs are 〈400-base extrachromosomal circles found in mammalian cells. Tens of thousands of microDNAs have been found in all tissue types, including sperm. MicroDNAs arise preferentially from areas with high gene density, GC content, and exon density from promoters with activating chromatin modifications and in sperm from the 5′-UTR of full-length LINE-1 elements, but are depleted from lamin-associated heterochromatin. Analysis of microDNAs from a set of human cancer cell lines revealed lineage-specific patterns of microDNA origins. A survey of microDNAs from chicken cells defective in various DNA repair proteins reveals that homologous recombination and non-homologous end joining repair pathways are not required for microDNA production. Deletion of the MSH3 DNA mismatch repair protein results in a significant decrease in microDNA abundance, specifically from non-CpG genomic regions. Thus, microDNAs arise as part of normal cellular physiology—either from DNA breaks associated with RNA metabolism or from replication slippage followed by mismatch repair. Graphical abstract Teaser Through isolating and sequencing small extrachromosomal circular microDNAs across multiple species and cell types, Dillon et al. identify specific genomic features associated with the generation of microDNAs and link the DNA mismatch repair pathway to this process.

Description: Publication date: Available online 4 June 2015 Source: Cell Reports Author(s): Caroline Ramspacher , Emily Steed , Francesco Boselli , Rita Ferreira , Nathalie Faggianelli , Stéphane Roth , Coralie Spiegelhalter , Nadia Messaddeq , Le Trinh , Michael Liebling , Nikhil Chacko , Federico Tessadori , Jeroen Bakkers , Jocelyn Laporte , Karim Hnia , Julien Vermot Desminopathies belong to a family of muscle disorders called myofibrillar myopathies that are caused by Desmin mutations and lead to protein aggregates in muscle fibers. To date, the initial pathological steps of desminopathies and the impact of desmin aggregates in the genesis of the disease are unclear. Using live, high-resolution microscopy, we show that Desmin loss of function and Desmin aggregates promote skeletal muscle defects and alter heart biomechanics. In addition, we show that the calcium dynamics associated with heart contraction are impaired and are associated with sarcoplasmic reticulum dilatation as well as abnormal subcellular distribution of Ryanodine receptors. Our results demonstrate that desminopathies are associated with perturbed excitation-contraction coupling machinery and that aggregates are more detrimental than Desmin loss of function. Additionally, we show that pharmacological inhibition of aggregate formation and Desmin knockdown revert these phenotypes. Our data suggest alternative therapeutic approaches and further our understanding of the molecular determinants modulating Desmin aggregate formation. Graphical abstract Teaser Desminopathies are myopathies and cardiomyopathies associated with Desmin mutations leading to protein aggregates. Ramspacher et al. demonstrate that altered Desmin function or expression affect the EC coupling machinery and calcium dynamics. They show that aggregates are more toxic than the loss of function and can be rescued by knockdown and pharmacological treatment.

Description: Publication date: Available online 4 June 2015 Source: Cell Reports Author(s): Peng Liu , Miranda N. Reed , Linda A. Kotilinek , Marianne K.O. Grant , Colleen L. Forster , Wei Qiang , Samantha L. Shapiro , John H. Reichl , Angie C.A. Chiang , Joanna L. Jankowsky , Carrie M. Wilmot , James P. Cleary , Kathleen R. Zahs , Karen H. Ashe The accumulation of amyloid-β (Aβ) as amyloid fibrils and toxic oligomers is an important step in the development of Alzheimer’s disease (AD). However, there are numerous potentially toxic oligomers and little is known about their neurological effects when generated in the living brain. Here we show that Aβ oligomers can be assigned to one of at least two classes (type 1 and type 2) based on their temporal, spatial, and structural relationships to amyloid fibrils. The type 2 oligomers are related to amyloid fibrils and represent the majority of oligomers generated in vivo, but they remain confined to the vicinity of amyloid plaques and do not impair cognition at levels relevant to AD. Type 1 oligomers are unrelated to amyloid fibrils and may have greater potential to cause global neural dysfunction in AD because they are dispersed. These results refine our understanding of the pathogenicity of Aβ oligomers in vivo. Graphical abstract Teaser Liu et al. classify brain-derived amyloid-β oligomers into type 1 and type 2. Type 2, but not type 1, oligomers have a spatiotemporal and structural relationship with amyloid plaques. Highly abundant type 2 oligomers do not impair cognition in situ, possibly due to spatial sequestration around plaques.

Description: Publication date: Available online 4 June 2015 Source: Cell Reports Author(s): Alessandro Fantin , Anastasia Lampropoulou , Gaia Gestri , Claudio Raimondi , Valentina Senatore , Ian Zachary , Christiana Ruhrberg Sprouting blood vessels are led by filopodia-studded endothelial tip cells that respond to angiogenic signals. Mosaic lineage tracing previously revealed that NRP1 is essential for tip cell function, although its mechanistic role in tip cells remains poorly defined. Here, we show that NRP1 is dispensable for genetic tip cell identity. Instead, we find that NRP1 is essential to form the filopodial bursts that distinguish tip cells morphologically from neighboring stalk cells, because it enables the extracellular matrix (ECM)-induced activation of CDC42, a key regulator of filopodia formation. Accordingly, NRP1 knockdown and pharmacological CDC42 inhibition similarly impaired filopodia formation in vitro and in developing zebrafish in vivo. During mouse retinal angiogenesis, CDC42 inhibition impaired tip cell and vascular network formation, causing defects that resembled those due to loss of ECM-induced, but not VEGF-induced, NRP1 signaling. We conclude that NRP1 enables ECM-induced filopodia formation for tip cell function during sprouting angiogenesis. Graphical abstract Teaser During angiogenesis, new blood vessel sprouts are led by filopodia-studded tip cells to sense environmental signals and enable directional migration. NRP1 is a tip cell protein that senses angiogenic cues. Fantin et al. now show that NRP1 promotes tip cell function by enabling CDC42 activation for filopodia formation and actin remodeling.

Description: Publication date: Available online 4 June 2015 Source: Cell Reports Author(s): Chien-Der Lee , Benjamin P. Tu PUF proteins are post-transcriptional regulators that bind to the 3′ UTRs of mRNA transcripts. Herein, we show how a yeast PUF protein, Puf3p, responds to glucose availability to switch the fate of its bound transcripts that encode proteins required for mitochondrial biogenesis. Upon glucose depletion, Puf3p becomes heavily phosphorylated within its N-terminal region of low complexity, associates with polysomes, and promotes translation of its target mRNAs. Such nutrient-responsive phosphorylation toggles the activity of Puf3p to promote either degradation or translation of these mRNAs according to the needs of the cell. Moreover, activation of translation of pre-existing mRNAs might enable rapid adjustment to environmental changes without the need for de novo transcription. Strikingly, a Puf3p phosphomutant no longer promotes translation but becomes trapped in intracellular foci in an mRNA-dependent manner. Our findings suggest that the inability to properly resolve Puf3p-containing RNA-protein granules via a phosphorylation-based mechanism might be toxic to a cell. Graphical abstract Teaser Lee and Tu report that the PUF protein Puf3 becomes phosphorylated in its low-complexity region upon glucose depletion to promote the translation of its bound mRNAs that are important for mitochondrial biogenesis. A Puf3 phosphomutant becomes trapped in punctate foci, providing insights into the dynamic nature of RNA granules.

Description: Publication date: Available online 4 June 2015 Source: Cell Reports Author(s): Takashi Izawa , Nidhi Rohatgi , Tomohiro Fukunaga , Qun-Tian Wang , Matthew J. Silva , Michael J. Gardner , Michael L. McDaniel , Nada A. Abumrad , Clay F. Semenkovich , Steven L. Teitelbaum , Wei Zou ASXL2 is an ETP family protein that interacts with PPARγ. We find that ASXL2−/− mice are insulin resistant, lipodystrophic, and fail to respond to a high-fat diet. Consistent with genetic variation at the ASXL2 locus and human bone mineral density, ASXL2−/− mice are also severely osteopetrotic because of failed osteoclast differentiation attended by normal bone formation. ASXL2 regulates the osteoclast via two distinct signaling pathways. It induces osteoclast formation in a PPARγ/c-Fos-dependent manner and is required for RANK ligand- and thiazolidinedione-induced bone resorption independent of PGC-1β. ASXL2 also promotes osteoclast mitochondrial biogenesis in a process mediated by PGC-1β but independent of c-Fos. Thus, ASXL2 is a master regulator of skeletal, lipid, and glucose homeostasis. Graphical abstract Teaser ASXL2 regulates glucose homeostasis, adipogenesis, and osteoclast differentiation by activating PPARγ. Izawa et al. find that ASXL2-deficient mice are insulin resistant, lipodystrophic, and osteopetrotic. ASXL2 promotes osteoclast formation in a Fos-dependent manner independent of PGC-1β. ASXL2 enhances osteoclast mitochondrial biogenesis in a process mediated by PGC-1β but independent of c-Fos.

Description: Publication date: Available online 4 June 2015 Source: Cell Reports Author(s): Jan-Philipp Mallm , Karsten Rippe Non-coding RNAs can modulate histone modifications that, at the same time, affect transcript expression levels. Here, we dissect such a network in mouse embryonic stem cells (ESCs). It regulates the activity of the reverse transcriptase telomerase, which synthesizes telomeric repeats at the chromosome ends. We find that histone H3 serine 10 phosphorylation set by Aurora kinase B (AURKB) in ESCs during the S phase of the cell cycle at centromeric and (sub)telomeric loci promotes the expression of non-coding minor satellite RNA ( cen RNA). Inhibition of AURKB induces silencing of cen RNA transcription and establishment of a repressive chromatin state with histone H3 lysine 9 trimethylation and heterochromatin protein 1 accumulation. This process results in a continuous shortening of telomeres. We further show that AURKB interacts with both telomerase and cen RNA and activates telomerase in trans . Thus, in mouse ESCs, telomere maintenance is regulated via expression of cen RNA in a cell-cycle-dependent manner. Graphical abstract Teaser Mallm and Rippe find that AURKB kinase and centromeric RNA regulate telomerase activity. AURKB phosphorylates serine 10 of histone H3 at chromosome p-arms during S phase in embryonic stem cells to induce centromere repeat transcription. Together, AURKB and centromere transcripts activate telomerase and ensure telomere maintenance.

Description: Publication date: Available online 6 August 2015 Source: Cell Reports Author(s): Jenea M. Bin, Dong Han, Karen Lai Wing Sun, Louis-Philippe Croteau, Emilie Dumontier, Jean-Francois Cloutier, Artur Kania, Timothy E. Kennedy Netrin-1 regulates cell migration and adhesion during the development of the nervous system, vasculature, lung, pancreas, muscle, and mammary gland. It is also proposed to function as a dependence ligand that inhibits apoptosis; however, studies disagree regarding whether netrin-1 loss-of-function mice exhibit increased cell death. Furthermore, previously studied netrin-1 loss-of-function gene-trap mice express a netrin-1-β-galactosidase protein chimera with potential for toxic gain-of-function effects, as well as a small amount of wild-type netrin-1 protein. To unambiguously assess loss of function, we generated netrin-1 floxed and netrin-1 null mouse lines. Netrin-1 −/− mice die earlier and exhibit more severe axon guidance defects than netrin-1 gene-trap mice, revealing that complete loss of function is more severe than previously reported. Netrin-1 −/− embryos also exhibit increased expression of the netrin receptors DCC and neogenin that are proposed dependence receptors; however, increased apoptosis was not detected, inconsistent with netrin-1 being an essential dependence receptor ligand in the embryonic spinal cord. Graphical abstract Teaser Bin et al. have generated a netrin-1 null mouse that displays phenotypes more severe than those of the reported netrin-1 gene-trap mouse, including embryonic lethality and exacerbated axon guidance defects. No increased apoptosis was detected, indicating that netrin-1 is not an essential dependence ligand, despite increased DCC and neogenin in netrin-1 nulls.

Description: Publication date: Available online 6 August 2015 Source: Cell Reports Author(s): Michael S. Werner, Alexander J. Ruthenburg A number of long noncoding RNAs (lncRNAs) have been reported to regulate transcription via recruitment of chromatin modifiers or bridging distal enhancer elements to gene promoters. However, the generality of these modes of regulation and the mechanisms of chromatin attachment for thousands of unstudied human lncRNAs remain unclear. To address these questions, we performed stringent nuclear fractionation coupled to RNA sequencing. We provide genome-wide identification of human chromatin-associated lncRNAs and demonstrate tethering of RNA to chromatin by RNAPII is a pervasive mechanism of attachment. We also uncovered thousands of chromatin-enriched RNAs (cheRNAs) that share molecular properties with known lncRNAs. Although distinct from eRNAs derived from active prototypical enhancers, the production of cheRNAs is strongly correlated with the expression of neighboring protein-coding genes. This work provides an updated framework for nuclear RNA organization that includes a large chromatin-associated transcript population correlated with active genes and may prove useful in de novo enhancer annotation. Graphical abstract Teaser Werner and Ruthenburg report a compendium of tightly chromatin-associated human lncRNAs, which is substantially larger than previously appreciated and also encompasses thousands of chromatin-enriched RNAs (cheRNAs) largely attached to chromatin via RNAPII. CheRNAs may provide a way to annotate enhancers de novo.

Description: Publication date: Available online 6 August 2015 Source: Cell Reports Author(s): Tony DeFalco, Sarah J. Potter, Alyna V. Williams, Brittain Waller, Matthew J. Kan, Blanche Capel The testis produces sperm throughout the male reproductive lifespan by balancing self-renewal and differentiation of spermatogonial stem cells (SSCs). Part of the SSC niche is thought to lie outside the seminiferous tubules of the testis; however, specific interstitial components of the niche that regulate spermatogonial divisions and differentiation remain undefined. We identified distinct populations of testicular macrophages, one of which lies on the surface of seminiferous tubules, in close apposition to areas of tubules enriched for undifferentiated spermatogonia. These macrophages express spermatogonial proliferation- and differentiation-inducing factors, such as colony-stimulating factor 1 (CSF1) and enzymes involved in retinoic acid (RA) biosynthesis. We show that transient depletion of macrophages leads to a disruption in spermatogonial differentiation. These findings reveal an unexpected role for macrophages in the spermatogonial niche in the testis and raise the possibility that macrophages play previously unappreciated roles in stem/progenitor cell regulation in other tissues. Graphical abstract Teaser Macrophages are abundant in the adult mammalian testis, but not much is known about how they directly affect spermatogenesis. DeFalco et al. describe a role for testicular macrophages, showing that they are enriched near spermatogonial precursors and are required for spermatogonial differentiation, potentially acting through CSF1 and retinoic acid pathways.

Description: Publication date: Available online 6 August 2015 Source: Cell Reports Author(s): Evgeny Ivashkin, Marina Yu. Khabarova, Victoria Melnikova, Leonid P. Nezlin, Olga Kharchenko, Elena E. Voronezhskaya, Igor Adameyko Many organisms survive in constantly changing environments, including cycling seasons. Developing embryos show remarkable instant adaptations to the variable environmental challenges they encounter during their adult life, despite having no direct contact with the changing environment until after birth or hatching. The mechanisms by which such non-genetic information is transferred to the developing embryos are largely unknown. Here, we address this question by using a freshwater pond snail ( Lymnaea stagnalis ) as a model system. This snail normally lives in a seasonal climate, and the seasons define its locomotion, feeding, and reproductive behavior. We discovered that the serotonergic system plays a crucial role in transmitting a non-genetic instructive signal from mother to progeny. This maternal serotonin-based signal functions in embryos during a short time window at exclusively early pre-neural developmental stages and modulates the dynamics of embryonic and juvenile growth, feeding behavior, and locomotion. Graphical abstract Teaser Ivashkin et al. reveal that maternally derived serotonin tunes the developmental dynamics and behavior of snail offspring under changing environmental conditions. The balance of intra- and extracellular serotonin exclusively during the non-neural stage of development, as well as serotonylation of proteins, is crucial for the transmission of a serotonin-based non-genetic signal.

Description: Publication date: Available online 6 August 2015 Source: Cell Reports Author(s): Cheng Li, Yahui Lan, Lianna Schwartz-Orbach, Evgenia Korol, Mamta Tahiliani, Todd Evans, Mary G. Goll The Tet family of methylcytosine dioxygenases (Tet1, Tet2, and Tet3) convert 5-methylcytosine to 5-hydroxymethylcytosine. To date, functional overlap among Tet family members has not been examined systematically in the context of embryonic development. To clarify the potential for overlap among Tet enzymes during development, we mutated the zebrafish orthologs of Tet1 , Tet2 , and Tet3 and examined single-, double-, and triple-mutant genotypes. Here, we identify Tet2 and Tet3 as the major 5-methylcytosine dioxygenases in the zebrafish embryo and uncover a combined requirement for Tet2 and Tet3 in hematopoietic stem cell (HSC) emergence. We demonstrate that Notch signaling in the hemogenic endothelium is regulated by Tet2/3 prior to HSC emergence and show that restoring expression of the downstream gata2b/scl/runx1 transcriptional network can rescue HSCs in tet2/3 double mutant larvae. Our results reveal essential, overlapping functions for tet genes during embryonic development and uncover a requirement for 5hmC in regulating HSC production. Graphical abstract Teaser The Tet proteins comprise a family of dioxygenases that convert 5-methylcytosine to 5-hydroxymethylcytosine. Li et al. identify Tet2 and Tet3 as the major 5-methylcytosine dioxygenases in the zebrafish embryo and uncover an overlapping requirement for Tet2 and Tet3 in hematopoietic stem cell emergence.

Description: Publication date: Available online 6 August 2015 Source: Cell Reports Author(s): Ann V. Griffith, Thomas Venables, Jianjun Shi, Andrew Farr, Holly van Remmen, Luke Szweda, Mohammad Fallahi, Peter Rabinovitch, Howard T. Petrie T lymphocytes are essential mediators of immunity that are produced by the thymus in proportion to its size. The thymus atrophies rapidly with age, resulting in progressive diminution of new T cell production. This decreased output is compensated by duplication of existing T cells, but it results in gradual dominance by memory T cells and decreased ability to respond to new pathogens or vaccines. Here, we show that accelerated and irreversible thymic atrophy results from stromal deficiency in the reducing enzyme catalase, leading to increased damage by hydrogen peroxide generated by aerobic metabolism. Genetic complementation of catalase in stromal cells diminished atrophy, as did chemical antioxidants, thus providing a mechanistic link between antioxidants, metabolism, and normal immune function. We propose that irreversible thymic atrophy represents a conventional aging process that is accelerated by stromal catalase deficiency in the context of an intensely anabolic (lymphoid) environment. Graphical abstract Teaser Thymic function is essential for maintenance of immunity but decreases with age. Griffith et al. show that stromal deficiency in catalase leads to mitochondrial dysfunction and DNA damage in stromal cells and that atrophy is ameliorated by genetic complementation of catalase or biochemical antioxidants.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Sergei A. Manakov, Dubravka Pezic, Georgi K. Marinov, William A. Pastor, Ravi Sachidanandam, Alexei A. Aravin In developing male germ cells, prospermatogonia, two Piwi proteins, MILI and MIWI2, use Piwi-interacting RNA (piRNA) guides to repress transposable element (TE) expression and ensure genome stability and proper gametogenesis. In addition to their roles in post-transcriptional TE repression, both proteins are required for DNA methylation of TE sequences. Here, we analyzed the effect of Miwi2 deficiency on piRNA biogenesis and transposon repression. Miwi2 deficiency had only a minor impact on piRNA biogenesis; however, the piRNA profile of Miwi2 -knockout mice indicated overexpression of several LINE1 TE families that led to activation of the ping-pong piRNA cycle. Furthermore, we found that MILI and MIWI2 have distinct functions in TE repression in the nucleus. MILI is responsible for DNA methylation of a larger subset of TE families than MIWI2 is, suggesting that the proteins have independent roles in establishing DNA methylation patterns. Graphical abstract Teaser Two components in the piRNA pathway, MILI and MIWI2, were proposed to work in a linear hierarchy to generate piRNAs and methylate transposon sequences. Manakov et al. now profile transcription and methylation patterns in Mili and Miwi2 mutants and demonstrate that these proteins are in part functionally independent.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Sang Woo Seo, Donghyuk Kim, Richard Szubin, Bernhard O. Palsson Three transcription factors (TFs), OxyR, SoxR, and SoxS, play a critical role in transcriptional regulation of the defense system for oxidative stress in bacteria. However, their full genome-wide regulatory potential is unknown. Here, we perform a genome-scale reconstruction of the OxyR, SoxR, and SoxS regulons in Escherichia coli K-12 MG1655. Integrative data analysis reveals that a total of 68 genes in 51 transcription units (TUs) belong to these regulons. Among them, 48 genes showed more than 2-fold changes in expression level under single-TF-knockout conditions. This reconstruction expands the genome-wide roles of these factors to include direct activation of genes related to amino acid biosynthesis (methionine and aromatic amino acids), cell wall synthesis (lipid A biosynthesis and peptidoglycan growth), and divalent metal ion transport (Mn 2+ , Zn 2+ , and Mg 2+ ). Investigating the co-regulation of these genes with other stress-response TFs reveals that they are independently regulated by stress-specific TFs. Graphical abstract Teaser Seo et al. reconstruct OxyR, SoxR, and SoxS transcriptional regulatory networks under oxidative stress in E. coli and expand their roles to include direct activation of amino acid biosynthesis, cell wall synthesis, and divalent metal ion transport. These processes are independently regulated by TFs specific to oxidative stress.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Anders S. Hansen, Erin K. O’Shea Although the relationship between DNA cis -regulatory sequences and gene expression has been extensively studied at steady state, how cis -regulatory sequences affect the dynamics of gene induction is not known. The dynamics of gene induction can be described by the promoter activation timescale (AcTime) and amplitude threshold (AmpThr). Combining high-throughput microfluidics with quantitative time-lapse microscopy, we control the activation dynamics of the budding yeast transcription factor, Msn2, and reveal how cis -regulatory motifs in 20 promoter variants of the Msn2-target-gene SIP18 affect AcTime and AmpThr. By modulating Msn2 binding sites, we can decouple AmpThr from AcTime and switch the SIP18 promoter class from high AmpThr and slow AcTime to low AmpThr and either fast or slow AcTime. We present a model that quantitatively explains gene-induction dynamics on the basis of the Msn2-binding-site number, TATA box location, and promoter nucleosome organization. Overall, we elucidate the cis- regulatory logic underlying promoter decoding of TF dynamics. Graphical abstract Teaser Cells control gene expression in part by regulating the dynamics of transcription-factor activity. Hansen and O’Shea investigate the cis -regulatory logic underlying promoter decoding of transcription-factor dynamics for 20 promoter variants and reveal that two properties characterizing the gene expression response—threshold and activation timescale—can be decoupled.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): David Lau, C. Peter Bengtson, Bettina Buchthal, Hilmar Bading The health of neurons is critically dependent on the relative signaling intensities of survival-promoting synaptic and death-inducing extrasynaptic NMDA receptors. Here, we show that BDNF is a regulator of this balance and promotes neuroprotection by reducing toxic NMDA receptor signaling. BDNF acts by initiating synaptic NMDA-receptor/nuclear-calcium-driven adaptogenomics, leading to increased expression of inhibin β- A ( inhba ). Inhibin β- A (its homodimer is known as activin A) in turn reduces neurotoxic extrasynaptic NMDA-receptor-mediated calcium influx, thereby shielding neurons against mitochondrial dysfunction, a major cause of excitotoxicity. Thus, BDNF induces acquired neuroprotection by enhancing synaptic activity and lowering extrasynaptic NMDA receptor death signaling through a nuclear calcium- inhibin β- A pathway. This process, which confers protection against ischemic brain damage in a mouse stroke model, may be compromised in Huntington’s disease, Alzheimer’s disease, or aging-related neurodegenerative conditions that are associated with reduced BDNF levels and/or enhanced extrasynaptic NMDA receptor signaling. Graphical abstract Teaser Lau et al. show that BDNF-induced neuroprotection is mediated by synaptic NMDA-receptor-dependent nuclear calcium signals activating transcription of inhibin β-A (activin A). Activin A in turn reduces toxic extrasynaptic NMDA-receptor-mediated calcium influx, shields neurons from mitochondrial dysfunction, and protects against stroke-induced brain damage.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Corina E. Antal, Julia A. Callender, Alexandr P. Kornev, Susan S. Taylor, Alexandra C. Newton The signaling output of protein kinase C (PKC) is exquisitely controlled, with its disruption resulting in pathophysiologies. Identifying the structural basis for autoinhibition is central to developing effective therapies for cancer, where PKC activity needs to be enhanced, or neurodegenerative diseases, where PKC activity should be inhibited. Here, we reinterpret a previously reported crystal structure of PKCβII and use docking and functional analysis to propose an alternative structure that is consistent with previous literature on PKC regulation. Mutagenesis of predicted contact residues establishes that the Ca 2+ -sensing C2 domain interacts intramolecularly with the kinase domain and the carboxyl-terminal tail, locking PKC in an inactive conformation. Ca 2+ -dependent bridging of the C2 domain to membranes provides the first step in activating PKC via conformational selection. Although the placement of the C1 domains remains to be determined, elucidation of the structural basis for autoinhibition of PKCβII unveils a unique direction for therapeutically targeting PKC. Graphical abstract Teaser Kinase autoinhibition is essential for suppressing signaling when appropriate signals are absent. Antal et al. reinterpret a protein kinase C βII crystal structure to show that its Ca 2+ -sensing C2 domain autoinhibits by binding over the kinase domain, unveiling an interface that can potentially be therapeutically targeted to enhance or restrain activity.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Yoosoo Yang, Jaewook Kim, Hye Yun Kim, Nayeon Ryoo, Sejin Lee, YoungSoo Kim, Hyewhon Rhim, Yeon-Kyun Shin Alzheimer’s disease (AD) is closely associated with synaptic dysfunction, and thus current treatments often aim to stimulate neurotransmission to improve cognitive impairment. Whereas the formation of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex is essential for synaptic transmission, the correlation between SNAREs and AD neuropathology is unknown. Here, we report that intracellular amyloid-β (Aβ) oligomers directly inhibit SNARE-mediated exocytosis by impairing SNARE complex formation. We observe abnormal reduction of SNARE complex levels in the brains of APP/PS1 transgenic (TG) mice compared to age-matched wild-types. We demonstrate that Aβ oligomers block SNARE complex assembly through the direct interaction with a target membrane (t)-SNARE syntaxin 1a in vitro. Furthermore, the results of the in vitro single-vesicle content-mixing assay reveal that Aβ oligomers inhibit SNARE-mediated fusion pores. Thus, our study identifies a potential molecular mechanism by which intracellular Aβ oligomers hamper SNARE-mediated exocytosis, likely leading to AD-associated synaptic dysfunctions. Graphical abstract Teaser The role of Aβ in cognitive impairment in Alzheimer’s disease still remains elusive. Yang et al. now show that Aβ oligomers bind to syntaxin 1a to impair SNARE complex formation to inhibit exocytosis. The resulting inhibition of neurotransmission could therefore lead to cognitive impairments.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Behnam Nabet, Pilib Ó Broin, Jaime M. Reyes, Kevin Shieh, Charles Y. Lin, Christine M. Will, Relja Popovic, Teresa Ezponda, James E. Bradner, Aaron A. Golden, Jonathan D. Licht Unrestrained receptor tyrosine kinase (RTK) signaling and epigenetic deregulation are root causes of tumorigenesis. We establish linkage between these processes by demonstrating that aberrant RTK signaling unleashed by oncogenic HRas G12V or loss of negative feedback through Sprouty gene deletion remodels histone modifications associated with active typical and super-enhancers. However, although both lesions disrupt the Ras-Erk axis, the expression programs, enhancer signatures, and transcription factor networks modulated upon HRas G12V transformation or Sprouty deletion are largely distinct. Oncogenic HRas G12V elevates histone 3 lysine 27 acetylation (H3K27ac) levels at enhancers near the transcription factor Gata4 and the kinase Prkcb, as well as their expression levels. We show that Gata4 is necessary for the aberrant gene expression and H3K27ac marking at enhancers, and Prkcb is required for the oncogenic effects of HRas G12V -driven cells. Taken together, our findings demonstrate that dynamic reprogramming of the cellular enhancer landscape is a major effect of oncogenic RTK signaling. Graphical abstract Teaser Aberrant receptor tyrosine kinase signaling mediated by oncogenic Ras or loss of Sprouty promotes tumorigenesis. Nabet et al. find that unrestrained receptor tyrosine signaling driven by these lesions alters distinct super-enhancers, transcription factors, and target genes. Gata4 and Prkcb are identified as mediators of the oncogenic program upon Ras transformation.

Description: Publication date: Available online 13 August 2015 Source: Cell Reports Author(s): Casandra Panea, Adam M. Farkas, Yoshiyuki Goto, Shahla Abdollahi-Roodsaz, Carolyn Lee, Balázs Koscsó, Kavitha Gowda, Tobias M. Hohl, Milena Bogunovic, Ivaylo I. Ivanov Generation of different CD4 T cell responses to commensal and pathogenic bacteria is crucial for maintaining a healthy gut environment, but the associated cellular mechanisms are poorly understood. Dendritic cells (DCs) and macrophages (Mfs) integrate microbial signals and direct adaptive immunity. Although the role of DCs in initiating T cell responses is well appreciated, how Mfs contribute to the generation of CD4 T cell responses to intestinal microbes is unclear. Th17 cells are critical for mucosal immune protection and at steady state are induced by commensal bacteria, such as segmented filamentous bacteria (SFB). Here, we examined the roles of mucosal DCs and Mfs in Th17 induction by SFB in vivo. We show that Mfs, and not conventional CD103 + DCs, are essential for the generation of SFB-specific Th17 responses. Thus, Mfs drive mucosal T cell responses to certain commensal bacteria. Graphical abstract Teaser How various mucosal mononuclear phagocyte subsets orchestrate immune responses to intestinal bacteria in vivo is poorly understood. Panea et al. identify intestinal macrophages as essential drivers of Th17 cell responses to certain commensal bacteria.

Description: Publication date: Available online 24 September 2015 Source: Cell Reports Author(s): Jan Dudeck, Shanawaz Mohammed Ghouse, Christian H.K. Lehmann, Anja Hoppe, Nadja Schubert, Sergei A. Nedospasov, Diana Dudziak, Anne Dudeck Mast cells are critical promoters of adaptive immunity in the contact hypersensitivity model, but the mechanism of allergen sensitization is poorly understood. Using Mcpt5-CreTNF FL/FL mice, we show here that the absence of TNF exclusively in mast cells impaired the expansion of CD8 + T cells upon sensitization and the T-cell-driven adaptive immune response to elicitation. T cells primed in the absence of mast cell TNF exhibited a diminished efficiency to transfer sensitization to naive recipients. Specifically, mast cell TNF promotes CD8 + dendritic cell (DC) maturation and migration to draining lymph nodes. The peripherally released mast cell TNF further critically boosts the CD8 + T-cell-priming efficiency of CD8 + DCs, thereby linking mast cell effects on T cells to DC modulation. Collectively, our findings identify the distinct potential of mast cell TNF to amplify CD8 + DC functionality and CD8 + T-cell-dominated adaptive immunity, which may be of great importance for immunotherapy and vaccination approaches. Graphical abstract Teaser The impact of mast cells on T-cell-dominated adaptive immunity and diseases is poorly mechanistically defined. Dudeck et al. identify the distinct potential of mast-cell-derived TNF to amplify CD8 + T cell expansion and CD8 + T-cell-driven adaptive immune responses by modulating the CD8 + DC migration and priming efficiency.

Description: Publication date: Available online 24 September 2015 Source: Cell Reports Author(s): Vincent Sarrazy, Sophie Sore, Manon Viaud, Guylène Rignol, Marit Westerterp, Franck Ceppo, Jean-Francois Tanti, Rodolphe Guinamard, Emmanuel L. Gautier, Laurent Yvan-Charvet Enhanced glucose utilization can be visualized in atherosclerotic lesions and may reflect a high glycolytic rate in lesional macrophages, but its causative role in plaque progression remains unclear. We observe that the activity of the carbohydrate-responsive element binding protein ChREBP is rapidly downregulated upon TLR4 activation in macrophages. ChREBP inactivation refocuses cellular metabolism to a high redox state favoring enhanced inflammatory responses after TLR4 activation and increased cell death after TLR4 activation or oxidized LDL loading. Targeted deletion of ChREBP in bone marrow cells resulted in accelerated atherosclerosis progression in Ldlr −/− mice with increased monocytosis, lesional macrophage accumulation, and plaque necrosis. Thus, ChREBP-dependent macrophage metabolic reprogramming hinders plaque progression and establishes a causative role for leukocyte glucose metabolism in atherosclerosis. Graphical abstract Teaser Sarrazy et al. show that the carbohydrate-responsive element binding protein ChREBP is required for metabolic reprogramming in activated macrophages and provide evidence that changes in ChREBP-dependent macrophage redox status influence macrophage polarization and survival with physiopathological consequences on atherosclerosis.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Samira Alliouachene, Benoit Bilanges, Gaëtan Chicanne, Karen E. Anderson, Wayne Pearce, Khaled Ali, Colin Valet, York Posor, Pei Ching Low, Claire Chaussade, Cheryl L. Scudamore, Rachel S. Salamon, Jonathan M. Backer, Len Stephens, Phill T. Hawkins, Bernard Payrastre, Bart Vanhaesebroeck In contrast to the class I phosphoinositide 3-kinases (PI3Ks), the organismal roles of the kinase activity of the class II PI3Ks are less clear. Here, we report that class II PI3K-C2β kinase-dead mice are viable and healthy but display an unanticipated enhanced insulin sensitivity and glucose tolerance, as well as protection against high-fat-diet-induced liver steatosis. Despite having a broad tissue distribution, systemic PI3K-C2β inhibition selectively enhances insulin signaling only in metabolic tissues. In a primary hepatocyte model, basal PI3P lipid levels are reduced by 60% upon PI3K-C2β inhibition. This results in an expansion of the very early APPL1-positive endosomal compartment and altered insulin receptor trafficking, correlating with an amplification of insulin-induced, class I PI3K-dependent Akt signaling, without impacting MAPK activity. These data reveal PI3K-C2β as a critical regulator of endosomal trafficking, specifically in insulin signaling, and identify PI3K-C2β as a potential drug target for insulin sensitization. Graphical abstract Teaser Organismal roles of class II PI3Ks are unclear. Alliouachene et al. show that inactivation of the class II PI3K-C2β in mice, by regulating insulin receptor trafficking, enhances insulin sensitivity and protects against high-fat-diet-induced liver steatosis. The results suggest that PI3K-C2β is a potential drug target for insulin sensitization.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Ramanathan Narayanan, Mehdi Pirouz, Cemil Kerimoglu, Linh Pham, Robin J. Wagener, Kamila A. Kiszka, Joachim Rosenbusch, Rho H. Seong, Michael Kessel, Andre Fischer, Anastassia Stoykova, Jochen F. Staiger, Tran Tuoc BAF (Brg/Brm-associated factors) complexes play important roles in development and are linked to chromatin plasticity at selected genomic loci. Nevertheless, a full understanding of their role in development and chromatin remodeling has been hindered by the absence of mutants completely lacking BAF complexes. Here, we report that the loss of BAF155/BAF170 in double-conditional knockout (dcKO) mice eliminates all known BAF subunits, resulting in an overall reduction in active chromatin marks (H3K9Ac), a global increase in repressive marks (H3K27me2/3), and downregulation of gene expression. We demonstrate that BAF complexes interact with H3K27 demethylases (JMJD3 and UTX) and potentiate their activity. Importantly, BAF complexes are indispensable for forebrain development, including proliferation, differentiation, and cell survival of neural progenitor cells. Our findings reveal a molecular mechanism mediated by BAF complexes that controls the global transcriptional program and chromatin state in development. Graphical abstract Teaser Narayanan et al. show that elimination of both core BAF155 and BAF170 subunits causes degradation of the BAF complexes and impairment of gene expression program in forebrain development. Mechanistically, BAF complexes control key chromatin modifications (H3K27Me2/3) by modulating the activity of H3K27 demethylases JMJD3/UTX.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Lena Seifert, Michael Deutsch, Sara Alothman, Dalia Alqunaibit, Gregor Werba, Mridul Pansari, Matthew Pergamo, Atsuo Ochi, Alejandro Torres-Hernandez, Elliot Levie, Daniel Tippens, Stephanie H. Greco, Shaun Tiwari, Nancy Ngoc Giao Ly, Andrew Eisenthal, Eliza van Heerden, Antonina Avanzi, Rocky Barilla, Constantinos P. Zambirinis, Mauricio Rendon, Donnele Daley, H. Leon Pachter, Cristina Hajdu, George Miller Dectin-1 is a C-type lectin receptor critical in anti-fungal immunity, but Dectin-1 has not been linked to regulation of sterile inflammation or oncogenesis. We found that Dectin-1 expression is upregulated in hepatic fibrosis and liver cancer. However, Dectin-1 deletion exacerbates liver fibro-inflammatory disease and accelerates hepatocarcinogenesis. Mechanistically, we found that Dectin-1 protects against chronic liver disease by suppressing TLR4 signaling in hepatic inflammatory and stellate cells. Accordingly, Dectin-1 –/– mice exhibited augmented cytokine production and reduced survival in lipopolysaccharide (LPS)-mediated sepsis, whereas Dectin-1 activation was protective. We showed that Dectin-1 inhibits TLR4 signaling by mitigating TLR4 and CD14 expression, which are regulated by Dectin-1-dependent macrophage colony stimulating factor (M-CSF) expression. Our study suggests that Dectin-1 is an attractive target for experimental therapeutics in hepatic fibrosis and neoplastic transformation. More broadly, our work deciphers critical cross-talk between pattern recognition receptors and implicates a role for Dectin-1 in suppression of sterile inflammation, inflammation-induced oncogenesis, and LPS-mediated sepsis. Graphical abstract Teaser Seifert et al. show Dectin-1 protects against chronic liver disease by suppressing TLR4 signaling via CD14 and M-CSF. This suggests that Dectin-1 is an attractive target for experimental therapeutics in hepatic fibrosis and transformation with implications for a role for Dectin-1 in suppression of sterile inflammation, inflammation-induced oncogenesis, and endotoxemia.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Elias Björnson, Bani Mukhopadhyay, Anna Asplund, Nusa Pristovsek, Resat Cinar, Stefano Romeo, Mathias Uhlen, George Kunos, Jens Nielsen, Adil Mardinoglu Hepatocellular carcinoma (HCC) is a deadly form of liver cancer that is increasingly prevalent. We analyzed global gene expression profiling of 361 HCC tumors and 49 adjacent noncancerous liver samples by means of combinatorial network-based analysis. We investigated the correlation between transcriptome and proteome of HCC and reconstructed a functional genome-scale metabolic model (GEM) for HCC. We identified fundamental metabolic processes required for cell proliferation using the network centric view provided by the GEM. Our analysis revealed tight regulation of fatty acid biosynthesis (FAB) and highly significant deregulation of fatty acid oxidation in HCC. We predicted mitochondrial acetate as an emerging substrate for FAB through upregulation of mitochondrial acetyl-CoA synthetase (ACSS1) in HCC. We analyzed heterogeneous expression of ACSS1 and ACSS2 between HCC patients stratified by high and low ACSS1 and ACSS2 expression and revealed that ACSS1 is associated with tumor growth and malignancy under hypoxic conditions in human HCC. Graphical abstract Teaser Stratification of HCC patients is vital for the development of effective treatment strategies. Björnson et al. stratify HCC patients based on acetate utilization and find that mitochondrial acetate is a metabolic fuel under hypoxic conditions. This is mediated by ACSS1, which may be a potential therapeutic target for treatment of HCC.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Aiming Ren, Yi Xue, Alla Peselis, Alexander Serganov, Hashim M. Al-Hashimi, Dinshaw J. Patel Naturally occurring L-glutamine riboswitches occur in cyanobacteria and marine metagenomes, where they reside upstream of genes involved in nitrogen metabolism. By combining X-ray, NMR, and MD, we characterized an L-glutamine-dependent conformational transition in the Synechococcus elongatus glutamine riboswitch from tuning fork to L-shaped alignment of stem segments. This transition generates an open ligand-binding pocket with L-glutamine selectivity enforced by Mg 2+ -mediated intermolecular interactions. The transition also stabilizes the P1 helix through a long-range “linchpin” Watson-Crick G-C pair-capping interaction, while melting a short helix below P1 potentially capable of modulating downstream readout. NMR data establish that the ligand-free glutamine riboswitch in Mg 2+ solution exists in a slow equilibrium between flexible tuning fork and a minor conformation, similar, but not identical, to the L-shaped bound conformation. We propose that an open ligand-binding pocket combined with a high conformational penalty for forming the ligand-bound state provide mechanisms for reducing binding affinity while retaining high selectivity. Graphical abstract Teaser Ren et al. report on the structural and dynamic basis of low-affinity, high-selectivity binding of L-glutamine by the glutamine riboswitch. Molecular recognition of the bound L-glutamine in an open pocket is driven by a long-range linchpin G-C pairing capping interaction, resulting in a tuning fork to L-shaped conformational transition.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Anne Teissier, Alexei Chemiakine, Benjamin Inbar, Sneha Bagchi, Russell S. Ray, Richard D. Palmiter, Susan M. Dymecki, Holly Moore, Mark S. Ansorge Despite the well-established role of serotonin signaling in mood regulation, causal relationships between serotonergic neuronal activity and behavior remain poorly understood. Using a pharmacogenetic approach, we find that selectively increasing serotonergic neuronal activity in wild-type mice is anxiogenic and reduces floating in the forced-swim test, whereas inhibition has no effect on the same measures. In a developmental mouse model of altered emotional behavior, increased anxiety and depression-like behaviors correlate with reduced dorsal raphé and increased median raphé serotonergic activity. These mice display blunted responses to serotonergic stimulation and behavioral rescues through serotonergic inhibition. Furthermore, we identify opposing consequences of dorsal versus median raphé serotonergic neuron inhibition on floating behavior, together suggesting that median raphé hyperactivity increases anxiety, whereas a low dorsal/median raphé serotonergic activity ratio increases depression-like behavior. Thus, we find a critical role of serotonergic neuronal activity in emotional regulation and uncover opposing roles of median and dorsal raphé function. Graphical abstract Teaser Teissier et al. report that acute activation of serotonergic neurons is anxiogenic. Inhibition has no effect in naive mice but restores normal behavior in a developmental model of anxiety and depression. Normalization of unbalanced serotonergic activity between the median and dorsal raphé nuclei likely underlies this beneficial effect.

Description: Publication date: Available online 25 November 2015 Source: Cell Reports Author(s): Isabel Siegert, Johannes Schödel, Manfred Nairz, Valentin Schatz, Katja Dettmer, Christopher Dick, Joanna Kalucka, Kristin Franke, Martin Ehrenschwender, Gunnar Schley, Angelika Beneke, Jörg Sutter, Matthias Moll, Claus Hellerbrand, Ben Wielockx, Dörthe M. Katschinski, Roland Lang, Bruno Galy, Matthias W. Hentze, Peppi Koivunen, Peter J. Oefner, Christian Bogdan, Günter Weiss, Carsten Willam, Jonathan Jantsch Both hypoxic and inflammatory conditions activate transcription factors such as hypoxia-inducible factor (HIF)-1α and nuclear factor (NF)-κB, which play a crucial role in adaptive responses to these challenges. In dendritic cells (DC), lipopolysaccharide (LPS)-induced HIF1α accumulation requires NF-κB signaling and promotes inflammatory DC function. The mechanisms that drive LPS-induced HIF1α accumulation under normoxia are unclear. Here, we demonstrate that LPS inhibits prolyl hydroxylase domain enzyme (PHD) activity and thereby blocks HIF1α degradation. Of note, LPS-induced PHD inhibition was neither due to cosubstrate depletion (oxygen or α-ketoglutarate) nor due to increased levels of reactive oxygen species, fumarate, and succinate. Instead, LPS inhibited PHD activity through NF-κB-mediated induction of the iron storage protein ferritin and subsequent decrease of intracellular available iron, a critical cofactor of PHD. Thus, hypoxia and LPS both induce HIF1α accumulation via PHD inhibition but deploy distinct molecular mechanisms (lack of cosubstrate oxygen versus deprivation of co-factor iron). Graphical abstract Teaser Siegert et al. find that the microbial cell wall component LPS reduces cytosolic free iron availability via induction of ferritin. Low free iron levels impair the prolyl hydroxylase domain enzyme (PHD) activity, thereby inhibiting hypoxia-inducible factor (HIF)-1α hydroxylation. This results in inflammatory HIF1α stabilization under normoxic conditions.

Description: Publication date: Available online 25 November 2015 Source: Cell Reports Author(s): Jeffrey M. Bhasin, Byron H. Lee, Lars Matkin, Margaret G. Taylor, Bo Hu, Yaomin Xu, Cristina Magi-Galluzzi, Eric A. Klein, Angela H. Ting A critical need in understanding the biology of prostate cancer is characterizing the molecular differences between indolent and aggressive cases. Because DNA methylation can capture the regulatory state of tumors, we analyzed differential methylation patterns genome-wide among benign prostatic tissue and low-grade and high-grade prostate cancer and found extensive, focal hypermethylation regions unique to high-grade disease. These hypermethylation regions occurred not only in the promoters of genes but also in gene bodies and at intergenic regions that are enriched for DNA-protein binding sites. Integration with existing RNA-sequencing (RNA-seq) and survival data revealed regions where DNA methylation correlates with reduced gene expression associated with poor outcome. Regions specific to aggressive disease are proximal to genes with distinct functions from regions shared by indolent and aggressive disease. Our compendium of methylation changes reveals crucial molecular distinctions between indolent and aggressive prostate cancer. Graphical abstract Teaser Bhasin et al. find that gains of DNA methylation at certain loci can distinguish indolent from aggressive forms of prostate cancer. These genomic regions of focal hypermethylation fall in diverse genomic contexts, are enriched for regulatory elements, and correlate with the expression of genes linked to poorer outcomes.

Description: Publication date: Available online 25 November 2015 Source: Cell Reports Author(s): Chong Yew Tan, Samuel Virtue, Guillaume Bidault, Martin Dale, Rachel Hagen, Julian L. Griffin, Antonio Vidal-Puig Although many transcriptional pathways regulating BAT have been identified, the role of lipid biosynthetic enzymes in thermogenesis has been less investigated. Whereas cold exposure causes changes in the fatty acid composition of BAT, the functional consequences of this remains relatively unexplored. In this study, we demonstrate that the enzyme Elongation of Very Long Chain fatty acids 6 (Elovl6) is necessary for the thermogenic action of BAT. Elovl6 is responsible for converting C16 non-essential fatty acids into C18 species. Loss of Elovl6 does not modulate traditional BAT markers; instead, it causes reduced expression of mitochondrial electron transport chain components and lower BAT thermogenic capacity. The reduction in BAT activity appears to be counteracted by increased beiging of scWAT. When beige fat is disabled by thermoneutrality or aging, Elovl6 KO mice gain weight and have increased scWAT mass and impaired carbohydrate metabolism. Overall, our study suggests fatty acid chain length is important for BAT function. Graphical abstract Teaser Tan et al. find that the elongation of non-essential C16 fatty acids to C18 species regulates mitochondrial function and is necessary for full recruitment of heat-generating brown adipose tissue.

Description: Publication date: Available online 25 November 2015 Source: Cell Reports Author(s): Ann-Britt Marcher, Anne Loft, Ronni Nielsen, Terhi Vihervaara, Jesper Grud Skat Madsen, Marko Sysi-Aho, Kim Ekroos, Susanne Mandrup Cold exposure greatly alters brown adipose tissue (BAT) gene expression and metabolism to increase thermogenic capacity. Here, we used RNA sequencing and mass-spectrometry-based lipidomics to provide a comprehensive resource describing the molecular signature of cold adaptation at the level of the transcriptome and lipidome. We show that short-term (3-day) cold exposure leads to a robust increase in expression of several brown adipocyte genes related to thermogenesis as well as the gene encoding the hormone irisin. However, pathway analysis shows that the most significantly induced genes are those involved in glycerophospholipid synthesis and fatty acid elongation. This is accompanied by significant changes in the acyl chain composition of triacylglycerols (TAGs) as well as subspecies-selective changes of acyl chains in glycerophospholipids. These results indicate that cold adaptation of BAT is associated with significant and highly species-selective remodeling of both TAGs and glycerophospholipids. Graphical abstract Teaser Using RNA-seq and mass-spectrometry-based lipidomics, Marcher et al. demonstrate that the early adaptation of brown adipose tissue to cold exposure entails induction of gene pathways involved in triacylglycerol and phospholipid metabolism and a highly selective remodeling of the glycerolipid content in the tissue.

Description: Publication date: Available online 25 November 2015 Source: Cell Reports Author(s): Robert A. Baldock, Matthew Day, Oliver J. Wilkinson, Ross Cloney, Penelope A. Jeggo, Antony W. Oliver, Felicity Z. Watts, Laurence H. Pearl 53BP1 plays multiple roles in mammalian DNA damage repair, mediating pathway choice and facilitating DNA double-strand break repair in heterochromatin. Although it possesses a C-terminal BRCT 2 domain, commonly involved in phospho-peptide binding in other proteins, initial recruitment of 53BP1 to sites of DNA damage depends on interaction with histone post-translational modifications—H4K20me2 and H2AK13/K15ub—downstream of the early γH2AX phosphorylation mark of DNA damage. We now show that, contrary to current models, the 53BP1-BRCT 2 domain binds γH2AX directly, providing a third post-translational mark regulating 53BP1 function. We find that the interaction of 53BP1 with γH2AX is required for sustaining the 53BP1-dependent focal concentration of activated ATM that facilitates repair of DNA double-strand breaks in heterochromatin in G1. Graphical abstract Teaser Baldock et al. find that the BRCT 2 domain of 53BP1 specifically recognizes γH2AX, the primary chromatin mark at DNA double-strand breaks. Mutational disruption of this recognition in cells affects pATM recruitment into foci in G1 and results in a defect in repair of DNA damage in heterochromatin.

Description: Publication date: Available online 25 November 2015 Source: Cell Reports Author(s): Yim Ling Cheng, Deborah J. Andrew Multiple inositol polyphosphate phosphatase (Mipp), a highly conserved but poorly understood histidine phosphatase, dephosphorylates higher-order IPs (IP 4 –IP 6 ) to IP 3 . To gain insight into the biological roles of these enzymes, we have characterized Drosophila mipp1 . mipp1 is dynamically expressed in the embryonic trachea, specifically in the leading cells of migrating branches at late stages, where Mipp1 localizes to the plasma membrane and filopodia. FGF signaling activates mipp1 expression in these cells, where extensive filopodia form to drive migration and elongation by cell intercalation. We show that Mipp1 facilitates formation and/or stabilization of filopodia in leading cells through its extracellular activity. mipp1 loss decreases filopodia number, whereas mipp1 overexpression increases filopodia number in a phosphatase-activity-dependent manner. Importantly, expression of Mipp1 gives cells a migratory advantage for the lead position in elongating tracheal branches. Altogether, these findings suggest that extracellular pools of inositol polyphosphates affect cell behavior during development. Graphical abstract Teaser Mipps are highly conserved enzymes that convert inositol polyphosphates (IP 6 , IP 5 , and IP 4 ) to IP 3 . Cheng and Andrew have demonstrated that Drosophila Mipp1 is highly expressed in cells of migrating branches of the developing trachea where it functions extracellularly to facilitate filopodia formation and confer migratory advantage.

Description: Publication date: Available online 25 November 2015 Source: Cell Reports Author(s): Christelle Glangetas, Giulia R. Fois, Marion Jalabert, Salvatore Lecca, Kristina Valentinova, Frank J. Meye, Marco Diana, Philippe Faure, Manuel Mameli, Stéphanie Caille, François Georges The ventral subiculum (vSUB) plays a key role in addiction, and identifying the neuronal circuits and synaptic mechanisms by which vSUB alters the excitability of dopamine neurons is a necessary step to understand the motor changes induced by cocaine. Here, we report that high-frequency stimulation of the vSUB (HFSvSUB) over-activates ventral tegmental area (VTA) dopamine neurons in vivo and triggers long-lasting modifications of synaptic transmission measured ex vivo. This potentiation is caused by NMDA-dependent plastic changes occurring in the bed nucleus of the stria terminalis (BNST). Finally, we report that the modification of the BNST-VTA neural circuits induced by HFSvSUB potentiates locomotor activity induced by a sub-threshold dose of cocaine. Our findings unravel a neuronal circuit encoding behavioral effects of cocaine in rats and highlight the importance of adaptive modifications in the BNST, a structure that influences motivated behavior as well as maladaptive behaviors associated with addiction. Graphical abstract Teaser Glangetas et al. show that the ventral subiculum alters the excitability of dopamine neurons in vivo via a relay within the bed nucleus of the stria terminalis, revealing a neuronal circuit controlling behavioral effects of cocaine.

Description: Publication date: Available online 25 November 2015 Source: Cell Reports Author(s): Duy Nguyen, Valérie Grenier St-Sauveur, Danny Bergeron, Fabien Dupuis-Sandoval, Michelle S. Scott, François Bachand Telomere maintenance by the telomerase reverse transcriptase requires a noncoding RNA subunit that acts as a template for the synthesis of telomeric repeats. In humans, the telomerase RNA (hTR) is a non-polyadenylated transcript produced from an independent transcriptional unit. As yet, the mechanism and factors responsible for hTR 3′ end processing have remained largely unknown. Here, we show that hTR is matured via a polyadenylation-dependent pathway that relies on the nuclear poly(A)-binding protein PABPN1 and the poly(A)-specific RNase PARN. Depletion of PABPN1 and PARN results in telomerase RNA deficiency and the accumulation of polyadenylated precursors. Accordingly, a deficiency in PABPN1 leads to impaired telomerase activity and telomere shortening. In contrast, we find that hTRAMP-dependent polyadenylation and exosome-mediated degradation function antagonistically to hTR maturation, thereby limiting telomerase RNA accumulation. Our findings unveil a critical requirement for RNA polyadenylation in telomerase RNA biogenesis, providing alternative approaches for telomerase inhibition in cancer. Graphical abstract Teaser Nguyen et al. present evidence that the functional, non-polyadenylated human telomerase RNA is matured via a 3′ end polyadenylation step that requires the poly(A)-specific factors PABPN1 and PARN. Their findings unveil a critical requirement for RNA polyadenylation in telomerase RNA biogenesis, providing alternative approaches for telomerase inhibition in cancer.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Shilpy Joshi, Denis Tolkunov, Hana Aviv, Abraham A. Hakimi, Ming Yao, James J. Hsieh, Shridar Ganesan, Chang S. Chan, Eileen White Oncocytomas are predominantly benign neoplasms possessing pathogenic mitochondrial mutations and accumulation of respiration-defective mitochondria, characteristics of unknown significance. Using exome and transcriptome sequencing, we identified two main subtypes of renal oncocytoma. Type 1 is diploid with CCND1 rearrangements, whereas type 2 is aneuploid with recurrent loss of chromosome 1, X or Y, and/or 14 and 21, which may proceed to more aggressive eosinophilic chromophobe renal cell carcinoma (ChRCC). Oncocytomas activate 5′ adenosine monophosphate-activated protein kinase (AMPK) and Tp53 (p53) and display disruption of Golgi and autophagy/lysosome trafficking, events attributed to defective mitochondrial function. This suggests that the genetic defects in mitochondria activate a metabolic checkpoint, producing autophagy impairment and mitochondrial accumulation that limit tumor progression, revealing a novel tumor-suppressive mechanism for mitochondrial inhibition with metformin. Alleviation of this metabolic checkpoint in type 2 by p53 mutations may allow progression to eosinophilic ChRCC, indicating that they represent higher risk. Graphical abstract Teaser Mechanisms that restrict tumors to benign disease inform approaches to cancer therapy. Joshi et al. report that genetic defects in mitochondrial respiration in benign oncocytomas block trafficking and activate p53, limiting tumor growth to benign disease.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Ana Sofia Rocha, Valerie Vidal, Marjolijn Mertz, Timothy J. Kendall, Aurelie Charlet, Hitoshi Okamoto, Andreas Schedl Liver zonation, the spatial separation of different metabolic pathways along the liver sinusoids, is fundamental for proper functioning of this organ, and its disruption can lead to the development of metabolic disorders such as hyperammonemia. Metabolic zonation involves the induction of β-catenin signaling around the central veins, but how this patterned activity is established and maintained is unclear. Here, we show that the signaling molecule Rspondin3 is specifically expressed within the endothelial compartment of the central vein. Conditional deletion of Rspo3 in mice disrupts activation of central fate, demonstrating its crucial role in determining and maintaining β-catenin-dependent zonation. Moreover, ectopic expression of Rspo1 , a close family member of Rspo3 , induces the expression of pericentral markers, demonstrating Rspondins to be sufficient to imprint a more central fate. Thus, Rspo3 is a key angiocrine factor that controls metabolic zonation of liver hepatocytes. Graphical abstract Teaser Liver zonation is crucial to permit the execution of the various metabolic functions of this organ. Rocha et al. show that RSPO3 is specifically expressed within endothelial cells of the central vein, where it acts on neighboring hepatocytes to establish and maintain liver zonation throughout life.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Osamu Sadakane, Yoshito Masamizu, Akiya Watakabe, Shin-Ichiro Terada, Masanari Ohtsuka, Masafumi Takaji, Hiroaki Mizukami, Keiya Ozawa, Hiroshi Kawasaki, Masanori Matsuzaki, Tetsuo Yamamori Two-photon imaging with genetically encoded calcium indicators (GECIs) enables long-term observation of neuronal activity in vivo. However, there are very few studies of GECIs in primates. Here, we report a method for long-term imaging of a GECI, GCaMP6f, expressed from adeno-associated virus vectors in cortical neurons of the adult common marmoset ( Callithrix jacchus ), a small New World primate. We used a tetracycline-inducible expression system to robustly amplify neuronal GCaMP6f expression and up- and downregulate it for more than 100 days. We succeeded in monitoring spontaneous activity not only from hundreds of neurons three-dimensionally distributed in layers 2 and 3 but also from single dendrites and axons in layer 1. Furthermore, we detected selective activities from somata, dendrites, and axons in the somatosensory cortex responding to specific tactile stimuli. Our results provide a way to investigate the organization and plasticity of cortical microcircuits at subcellular resolution in non-human primates. Graphical abstract Teaser Long-term two-photon calcium imaging has been challenging in non-human primates. Sadakane et al. use an inducible expression system to visualize cortical neurons in adult marmosets. They show that the same neuronal population can be followed over 100 days and neuronal responses to tactile stimulation can be imaged at subcellular resolution.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Kei Sugihara, Koichi Nishiyama, Shigetomo Fukuhara, Akiyoshi Uemura, Satoshi Arima, Ryo Kobayashi, Alvaro Köhn-Luque, Naoki Mochizuki, Toshio Suda, Hisao Ogawa, Hiroki Kurihara Angiogenesis is a multicellular phenomenon driven by morphogenetic cell movements. We recently reported morphogenetic vascular endothelial cell (EC) behaviors to be dynamic and complex. However, the principal mechanisms orchestrating individual EC movements in angiogenic morphogenesis remain largely unknown. Here we present an experiment-driven mathematical model that enables us to systematically dissect cellular mechanisms in branch elongation. We found that cell-autonomous and coordinated actions governed these multicellular behaviors, and a cell-autonomous process sufficiently illustrated essential features of the morphogenetic EC dynamics at both the single-cell and cell-population levels. Through refining our model and experimental verification, we further identified a coordinated mode of tip EC behaviors regulated via a spatial relationship between tip and follower ECs, which facilitates the forward motility of tip ECs. These findings provide insights that enhance our mechanistic understanding of not only angiogenic morphogenesis, but also other types of multicellular phenomenon. Graphical abstract Teaser Angiogenesis is a multicellular phenomenon driven by morphogenetic cell movements. By combining experimental and modeling assays, Sugihara et al. demonstrate cell-autonomous and coordinated aspects of morphogenesis to be governed by multicellular behaviors, which provides insights allowing angiogenic morphogenesis to be understood systematically.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Kurt C. Marsden, Michael Granato Exposure to repetitive startling stimuli induces habitation, a simple form of learning. Despite its simplicity, the precise cellular mechanisms by which repeated stimulation converts a robust behavioral response to behavioral indifference are unclear. Here, we use head-restrained zebrafish larvae to monitor subcellular Ca 2+ dynamics in Mauthner neurons, the startle command neurons, during startle habituation in vivo. Using the Ca 2+ reporter GCaMP6s, we find that the amplitude of Ca 2+ signals in the lateral dendrite of the Mauthner neuron determines startle probability and that depression of this dendritic activity rather than downstream inhibition mediates glycine and N-methyl-D-aspartate (NMDA)-receptor-dependent short-term habituation. Combined, our results suggest a model for habituation learning in which increased inhibitory drive from feedforward inhibitory neurons combined with decreased excitatory input from auditory afferents decreases dendritic and Mauthner neuron excitability. Graphical abstract Teaser The neuronal mechanisms that govern short-term habituation of the startle response are unclear. Using GCaMP6s to visualize subcellular activity in the zebrafish startle command neuron, the Mauthner cell, Marsden and Granato show that depression of dendritic excitability rather than downstream inhibition underlies short-term habituation.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Michiel M. ten Brinke, Henk-Jan Boele, Jochen K. Spanke, Jan-Willem Potters, Katja Kornysheva, Peer Wulff, Anna C.H.G. IJpelaar, Sebastiaan K.E. Koekkoek, Chris I. De Zeeuw Three decades of electrophysiological research on cerebellar cortical activity underlying Pavlovian conditioning have expanded our understanding of motor learning in the brain. Purkinje cell simple spike suppression is considered to be crucial in the expression of conditional blink responses (CRs). However, trial-by-trial quantification of this link in awake behaving animals is lacking, and current hypotheses regarding the underlying plasticity mechanisms have diverged from the classical parallel fiber one to the Purkinje cell synapse LTD hypothesis. Here, we establish that acquired simple spike suppression, acquired conditioned stimulus (CS)-related complex spike responses, and molecular layer interneuron (MLI) activity predict the expression of CRs on a trial-by-trial basis using awake behaving mice. Additionally, we show that two independent transgenic mouse mutants with impaired MLI function exhibit motor learning deficits. Our findings suggest multiple cerebellar cortical plasticity mechanisms underlying simple spike suppression, and they implicate the broader involvement of the olivocerebellar module within the interstimulus interval. Graphical abstract Teaser Purkinje cell simple spike suppression is a central driving mechanism in cerebellar conditioning. Here, ten Brinke et al. show how simple spike suppression, conditioned stimulus-related complex spikes, and molecular layer interneuron (MLI) activity correlate to conditioned eyelid behavior. Moreover, transgenic impairment of MLI input results in deficits in conditioned behavior.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Jon-Matthew Belton, Bryan R. Lajoie, Sylvain Audibert, Sylvain Cantaloube, Imen Lassadi, Isabelle Goiffon, Davide Baù, Marc A. Marti-Renom, Kerstin Bystricky, Job Dekker Mating-type switching in yeast occurs through gene conversion between the MAT locus and one of two silent loci ( HML or HMR ) on opposite ends of the chromosome. MAT a cells choose HML as template, whereas MAT α cells use HMR . The recombination enhancer (RE) located on the left arm regulates this process. One long-standing hypothesis is that switching is guided by mating-type-specific and possibly RE-dependent chromosome folding. Here, we use Hi-C, 5C, and live-cell imaging to characterize the conformation of chromosome III in both mating types. We discovered a mating-type-specific conformational difference in the left arm. Deletion of a 1-kb subregion within the RE, which is not necessary during switching, abolished mating-type-dependent chromosome folding. The RE is therefore a composite element with one subregion essential for donor selection during switching and a separate region involved in modulating chromosome conformation. Graphical abstract Teaser Yeast mating-type switching involves a mating-type-dependent selection of either the left ( HML ) or right silent mating-type locus ( HMR ) on chromosome III for gene conversion with the active MAT locus. One hypothesis has been that this involves differential folding of the chromosome. Belton et al. now show that a 1-kb cis -element located within the larger recombination enhancer determines mating-type-dependent chromosome folding so that in MAT a cells HML associates with the centromere and MAT locus more frequently than in MAT α cells.

Description: Publication date: Available online 19 November 2015 Source: Cell Reports Author(s): Katarzyna Koltowska, Anne Karine Lagendijk, Cathy Pichol-Thievend, Johanna C. Fischer, Mathias Francois, Elke A. Ober, Alpha S. Yap, Benjamin M. Hogan Lymphatic vessels arise chiefly from preexisting embryonic veins. Genetic regulators of lymphatic fate are known, but how dynamic cellular changes contribute during the acquisition of lymphatic identity is not understood. We report the visualization of zebrafish lymphatic precursor cell dynamics during fate restriction. In the cardinal vein, cellular commitment is linked with the division of bipotential Prox1-positive precursor cells, which occurs immediately prior to sprouting angiogenesis. Following precursor division, identities are established asymmetrically in daughter cells; one daughter cell becomes lymphatic and progressively upregulates Prox1, and the other downregulates Prox1 and remains in the vein. Vegfc drives cell division and Prox1 expression in lymphatic daughter cells, coupling signaling dynamics with daughter cell fate restriction and precursor division. Graphical abstract Teaser Using live imaging, Koltowska and Lagendijk et al. identify bipotential Prox1-expressing precursor cells that divide to generate daughter cells with distinct identities. Following Vegfc-driven cell division, a venous daughter cell remains in the vein and a lymphatic daughter cell leaves, a process by which one vascular lineage derives from another.

Description: Publication date: Available online 25 November 2015 Source: Cell Reports Author(s): Domenico Iuso, Marta Czernik, Paola Toschi, Antonella Fidanza, Federica Zacchini, Robert Feil, Sandrine Curtet, Thierry Buchou, Hitoshi Shiota, Saadi Khochbin, Grazyna Ewa Ptak, Pasqualino Loi Protamines confer a compact structure to the genome of male gametes. Here, we find that somatic cells can be remodeled by transient expression of protamine 1 (Prm1). Ectopically expressed Prm1 forms scattered foci in the nuclei of fibroblasts, which coalescence into spermatid-like structures, concomitant with a loss of histones and a reprogramming barrier, H3 lysine 9 methylation. Protaminized nuclei injected into enucleated oocytes efficiently underwent protamine to maternal histone TH2B exchange and developed into normal blastocyst stage embryos in vitro. Altogether, our findings present a model to study male-specific chromatin remodeling, which can be exploited for the improvement of somatic cell nuclear transfer. Graphical abstract Teaser Iuso et al. find that exogenous expression of human protamine 1 remodels interphase fibroblast nuclei into spermatid-like structures. The process is reversible upon nuclear transfer into enucleated oocytes. This finding could be exploited as a simplified model for investigating protamine-induced genome compaction and may also boost somatic cell nuclear transfer efficiency.

Description: Publication date: Available online 28 August 2015 Source: Cell Reports Author(s): Ola B. Nilsson, Rickard Hedman, Jacopo Marino, Stephan Wickles, Lukas Bischoff, Magnus Johansson, Annika Müller-Lucks, Fabio Trovato, Joseph D. Puglisi, Edward P. O’Brien, Roland Beckmann, Gunnar von Heijne At what point during translation do proteins fold? It is well established that proteins can fold cotranslationally outside the ribosome exit tunnel, whereas studies of folding inside the exit tunnel have so far detected only the formation of helical secondary structure and collapsed or partially structured folding intermediates. Here, using a combination of cotranslational nascent chain force measurements, inter-subunit fluorescence resonance energy transfer studies on single translating ribosomes, molecular dynamics simulations, and cryoelectron microscopy, we show that a small zinc-finger domain protein can fold deep inside the vestibule of the ribosome exit tunnel. Thus, for small protein domains, the ribosome itself can provide the kind of sheltered folding environment that chaperones provide for larger proteins. Graphical abstract Teaser Nilsson et al. present an integrated approach to the study of cotranslational protein folding, in which the folding transition is mapped by arrest-peptide-mediated force measurements, molecular dynamics simulations, and cryo-EM (electron microscopy). The small zinc-finger domain ADR1a is shown to fold deep inside the ribosome exit tunnel.

Description: Publication date: Available online 28 August 2015 Source: Cell Reports Author(s): Kiyoto Kurima, Seham Ebrahim, Bifeng Pan, Miloslav Sedlacek, Prabuddha Sengupta, Bryan A. Millis, Runjia Cui, Hiroshi Nakanishi, Taro Fujikawa, Yoshiyuki Kawashima, Byung Yoon Choi, Kelly Monahan, Jeffrey R. Holt, Andrew J. Griffith, Bechara Kachar Mechanosensitive ion channels at stereocilia tips mediate mechanoelectrical transduction (MET) in inner ear sensory hair cells. Transmembrane channel-like 1 and 2 (TMC1 and TMC2) are essential for MET and are hypothesized to be components of the MET complex, but evidence for their predicted spatiotemporal localization in stereocilia is lacking. Here, we determine the stereocilia localization of the TMC proteins in mice expressing TMC1-mCherry and TMC2-AcGFP. Functionality of the tagged proteins was verified by transgenic rescue of MET currents and hearing in Tmc1 Δ/Δ ; Tmc2 Δ/Δ mice. TMC1-mCherry and TMC2-AcGFP localize along the length of immature stereocilia. However, as hair cells develop, the two proteins localize predominantly to stereocilia tips. Both TMCs are absent from the tips of the tallest stereocilia, where MET activity is not detectable. This distribution was confirmed for the endogenous proteins by immunofluorescence. These data are consistent with TMC1 and TMC2 being components of the stereocilia MET channel complex. Graphical abstract Teaser The molecular makeup of hair cell mechanoelectrical transduction (MET) complex remains elusive. Kurima et al. show that fluorophore-tagged TMC1/2 localize to MET sites at stereocilia tips and that their expression in TMC1/2-null mice rescues MET. These findings support the model that TMC1/2 are part of the MET complex.

Description: Publication date: Available online 28 August 2015 Source: Cell Reports Author(s): Tobias Schatton, Jun Yang, Sonja Kleffel, Mayuko Uehara, Steven R. Barthel, Christoph Schlapbach, Qian Zhan, Stephen Dudeney, Hansgeorg Mueller, Nayoung Lee, Juliane C. de Vries, Barbara Meier, Seppe Vander Beken, Mark A. Kluth, Christoph Ganss, Arlene H. Sharpe, Ana Maria Waaga-Gasser, Mohamed H. Sayegh, Reza Abdi, Karin Scharffetter-Kochanek, George F. Murphy, Thomas S. Kupper, Natasha Y. Frank, Markus H. Frank Cell-based strategies represent a new frontier in the treatment of immune-mediated disorders. However, the paucity of markers for isolation of molecularly defined immunomodulatory cell populations poses a barrier to this field. Here, we show that ATP-binding cassette member B5 (ABCB5) identifies dermal immunoregulatory cells (DIRCs) capable of exerting therapeutic immunoregulatory functions through engagement of programmed cell death 1 (PD-1). Purified Abcb5 + DIRCs suppressed T cell proliferation, evaded immune rejection, homed to recipient immune tissues, and induced Tregs in vivo. In fully major-histocompatibility-complex-mismatched cardiac allotransplantation models, allogeneic DIRCs significantly prolonged allograft survival. Blockade of DIRC-expressed PD-1 reversed the inhibitory effects of DIRCs on T cell activation, inhibited DIRC-dependent Treg induction, and attenuated DIRC-induced prolongation of cardiac allograft survival, indicating that DIRC immunoregulatory function is mediated, at least in part, through PD-1. Our results identify ABCB5 + DIRCs as a distinct immunoregulatory cell population and suggest promising roles of this expandable cell subset in cellular immunotherapy. Graphical abstract Teaser Schatton et al. identify ABCB5 as a marker of dermal cells in mammalian skin that possess immunoregulatory functions, through engagement of the immune checkpoint molecule PD-1. ABCB5-positive cells, when administered to recipients of heart transplants in preclinical models, prolong graft survival, suggesting promising roles of this cell subset in cellular immunotherapy.

Description: Publication date: Available online 28 August 2015 Source: Cell Reports Author(s): Alyson A. Fiorillo, Christopher R. Heier, James S. Novak, Christopher B. Tully, Kristy J. Brown, Kitipong Uaesoontrachoon, Maria C. Vila, Peter P. Ngheim, Luca Bello, Joe N. Kornegay, Corrado Angelini, Terence A. Partridge, Kanneboyina Nagaraju, Eric P. Hoffman The amount and distribution of dystrophin protein in myofibers and muscle is highly variable in Becker muscular dystrophy and in exon-skipping trials for Duchenne muscular dystrophy. Here, we investigate a molecular basis for this variability. In muscle from Becker patients sharing the same exon 45–47 in-frame deletion, dystrophin levels negatively correlate with microRNAs predicted to target dystrophin. Seven microRNAs inhibit dystrophin expression in vitro, and three are validated in vivo (miR-146b/miR-374a/miR-31). microRNAs are expressed in dystrophic myofibers and increase with age and disease severity. In exon-skipping-treated mdx mice, microRNAs are significantly higher in muscles with low dystrophin rescue. TNF-α increases microRNA levels in vitro whereas NFκB inhibition blocks this in vitro and in vivo. Collectively, these data show that microRNAs contribute to variable dystrophin levels in muscular dystrophy. Our findings suggest a model where chronic inflammation in distinct microenvironments induces pathological microRNAs, initiating a self-sustaining feedback loop that exacerbates disease progression. Graphical abstract Teaser Fiorillo et al. find that miRNAs in muscle promote variable dystrophin levels in muscular dystrophies. Dystrophin-targeting miRNAs reduce dystrophin and increase with disease severity. Innate inflammatory pathways induce miRNAs, whereas NFκB inhibition dampens induction. These events initiate a self-sustaining feedback loop, exacerbating disease progression. Thus, miRNA inhibition in dystrophic muscle could provide therapeutic targets.

Description: Publication date: Available online 28 May 2015 Source: Cell Reports Author(s): Kristin K. Brown , Laleh Montaser-Kouhsari , Andrew H. Beck , Alex Toker Resistance to cytotoxic chemotherapy drugs, including doxorubicin, is a significant obstacle to the effective treatment of breast cancer. Here, we have identified a mechanism by which the PI3K/Akt pathway mediates resistance to doxorubicin. In addition to inducing DNA damage, doxorubicin triggers sustained activation of Akt signaling in breast cancer cells. We show that Akt contributes to chemotherapy resistance such that PI3K or Akt inhibitors sensitize cells to doxorubicin. We identify MERIT40, a component of the BRCA1-A DNA damage repair complex, as an Akt substrate that is phosphorylated following doxorubicin treatment. MERIT40 phosphorylation facilitates assembly of the BRCA1-A complex in response to DNA damage and contributes to DNA repair and cell survival following doxorubicin treatment. Finally, MERIT40 phosphorylation in human breast cancers is associated with estrogen receptor positivity. Our findings suggest that combination therapy with PI3K or Akt inhibitors and doxorubicin may constitute a successful strategy for overcoming chemotherapy resistance. Graphical abstract Teaser Brown et al. show that doxorubicin triggers activation of Akt signaling and phosphorylation of MERIT40, a component of the BRCA1-A DNA repair complex. MERIT40 phosphorylation contributes to DNA repair and cell survival following doxorubicin exposure. Inhibition of Akt signaling and MERIT40 phosphorylation sensitize breast cancer cells to doxorubicin.

Description: Publication date: Available online 28 May 2015 Source: Cell Reports Author(s): Hyungsoo Kim , Dennie T. Frederick , Mitchell P. Levesque , Zachary A. Cooper , Yongmei Feng , Clemens Krepler , Laurence Brill , Yardena Samuels , Nicholas K. Hayward , Ally Perlina , Adriano Piris , Tongwu Zhang , Ruth Halaban , Meenhard M. Herlyn , Kevin M. Brown , Jennifer A. Wargo , Reinhard Dummer , Keith T. Flaherty , Ze’ev A. Ronai Despite the remarkable clinical response of melanoma harboring BRAF mutations to BRAF inhibitors (BRAFi), most tumors become resistant. Here, we identified the downregulation of the ubiquitin ligase RNF125 in BRAFi-resistant melanomas and demonstrated its role in intrinsic and adaptive resistance to BRAFi in cultures as well as its association with resistance in tumor specimens. Sox10/MITF expression correlated with and contributed to RNF125 transcription. Reduced RNF125 was associated with elevated expression of receptor tyrosine kinases (RTKs), including EGFR. Notably, RNF125 altered RTK expression through JAK1, which we identified as an RNF125 substrate. RNF125 bound to and ubiquitinated JAK1, prompting its degradation and suppressing RTK expression. Inhibition of JAK1 and EGFR signaling overcame BRAFi resistance in melanoma with reduced RNF125 expression, as shown in culture and in in vivo xenografts. Our findings suggest that combination therapies targeting both JAK1 and EGFR could be effective against BRAFi-resistant tumors with de novo low RNF125 expression. Graphical abstract Teaser Kim et al. find that the RNF125 ubiquitin ligase is downregulated in BRAF inhibitor (BRAFi)-resistant melanomas, resulting in increased expression of its identified substrate, JAK1, with a concomitant increase in EGFR expression. The combination of JAK, EGRF, and BRAF inhibitors effectively overcomes melanoma resistance. The low level of RNF125 seen in melanoma specimens inversely correlates with BRAFi resistance.

Description: Publication date: Available online 28 May 2015 Source: Cell Reports Author(s): Zilton Vasconcelos , Sabina Müller , Delphine Guipouy , Wong Yu , Claire Christophe , Sébastien Gadat , Salvatore Valitutti , Loïc Dupré The killing of antigen-bearing cells by clonal populations of cytotoxic T lymphocytes (CTLs) is thought to be a rapid phenomenon executed uniformly by individual CTLs. We combined bulk and single-CTL killing assays over a prolonged time period to provide the killing statistics of clonal human CTLs against an excess of target cells. Our data reveal efficiency in sustained killing at the population level, which relied on a highly heterogeneous multiple killing performance at the individual level. Although intraclonal functional heterogeneity was a stable trait in clonal populations, it was reset in the progeny of individual CTLs. In-depth mathematical analysis of individual CTL killing data revealed a substantial proportion of high-rate killer CTLs with burst killing activity. Importantly, such activity was delayed and required activation with strong antigenic stimulation. Our study implies that functional heterogeneity allows CTL populations to calibrate prolonged cytotoxic activity to the size of target cell populations. Graphical abstract Teaser Cytotoxicity is viewed as a rapid and homogeneous response of CTLs to antigen-bearing target cells. Vasconcelos et al. report that human CTL clones are endowed with a sustained cytotoxic activity when facing an excess of target cells. Such activity relies on a high heterogeneity of individual CTL killing performances, whereby only a subset of high-rate killer CTLs develop with time. The authors propose that these CTL traits are key to the calibration of cytotoxic responses.

Description: Publication date: Available online 28 May 2015 Source: Cell Reports Author(s): Samantha M. Solon-Biet , Sarah J. Mitchell , Sean C.P. Coogan , Victoria C. Cogger , Rahul Gokarn , Aisling C. McMahon , David Raubenheimer , Rafael de Cabo , Stephen J. Simpson , David G. Le Couteur Both caloric restriction (CR) and low-protein, high-carbohydrate (LPHC) ad-libitum - fed diets increase lifespan and improve metabolic parameters such as insulin, glucose, and blood lipids. Severe CR, however, is unsustainable for most people; therefore, it is important to determine whether manipulating macronutrient ratios in ad-libitum-fed conditions can generate similar health outcomes. We present the results of a short-term (8 week) dietary manipulation on metabolic outcomes in mice. We compared three diets varying in protein to carbohydrate ratio under both CR and ad libitum conditions. Ad libitum LPHC diets delivered similar benefits to CR in terms of levels of insulin, glucose, lipids, and HOMA, despite increased energy intake. CR on LPHC diets did not provide additional benefits relative to ad libitum LPHC. We show that LPHC diets under ad-libitum-fed conditions generate the metabolic benefits of CR without a 40% reduction in total caloric intake. Graphical abstract Teaser Nutritional interventions improve metabolic health in mice. Solon-Biet et al. find that short-term ad libitum low-protein, high-carbohydrate (LPHC) diets improve levels of insulin, glucose, lipids, and HOMA. LPHC diets under ad-libitum-fed conditions generate the metabolic benefits of caloric restriction without a 40% reduction in total caloric intake.

Description: Publication date: Available online 28 May 2015 Source: Cell Reports Author(s): Riikka H. Hämäläinen , Kati J. Ahlqvist , Pekka Ellonen , Maija Lepistö , Angela Logan , Timo Otonkoski , Michael P. Murphy , Anu Suomalainen mtDNA mutagenesis in somatic stem cells leads to their dysfunction and to progeria in mouse. The mechanism was proposed to involve modification of reactive oxygen species (ROS)/redox signaling. We studied the effect of mtDNA mutagenesis on reprogramming and stemness of pluripotent stem cells (PSCs) and show that PSCs select against specific mtDNA mutations, mimicking germline and promoting mtDNA integrity despite their glycolytic metabolism. Furthermore, mtDNA mutagenesis is associated with an increase in mitochondrial H 2 O 2 , reduced PSC reprogramming efficiency, and self-renewal. Mitochondria-targeted ubiquinone, MitoQ, and N-acetyl-L-cysteine efficiently rescued these defects, indicating that both reprogramming efficiency and stemness are modified by mitochondrial ROS. The redox sensitivity, however, rendered PSCs and especially neural stem cells sensitive to MitoQ toxicity. Our results imply that stem cell compartment warrants special attention when the safety of new antioxidants is assessed and point to an essential role for mitochondrial redox signaling in maintaining normal stem cell function. Graphical abstract Teaser Hämäläinen et al. show that stem cell homeostasis and reprogramming efficiency are sensitive to mitochondrial mutagenesis and mitochondria-derived oxygen radicals, which decrease stemness. The stem cell sensitivity to redox signaling also makes them sensitive targets for antioxidants, which, if targeted to mitochondria, show dose-dependent benefits or toxicity.

Description: Publication date: Available online 28 May 2015 Source: Cell Reports Author(s): Sean P. Cullen , Conor J. Kearney , Danielle M. Clancy , Seamus J. Martin The NLRP3 inflammasome is involved in caspase-1-dependent maturation of IL-1β in many contexts. A two-signal model has emerged for IL-1β maturation, with LPS providing “signal I” and diverse agents such as ATP, Nigericin, streptolysin O, uric acid crystals, and alum salts capable of acting as “signal II.” In the absence of signal II, pro-IL-1β is upregulated but typically fails to be processed or released. What unites signal II stimuli has been debated, with the ability to promote K+ efflux suggested as a common factor, but the mechanism of IL-1β release remains unclear. Here, we show that all examined inflammasome signal II agents triggered necrosis, which was highly correlated with their ability to promote IL-1β release. IL-1β secretion occurred in tandem with the release of many additional proteins and was confined to necrotic cells. Thus, signal II agents initiate inflammation by promoting necrosis-driven IL-1β release, suggesting that IL-1β represents an inducible danger signal. Graphical abstract Teaser A two-signal model has emerged for NLRP3 inflammasome-dependent IL-1β maturation, but the mechanism of IL-1β release remains unclear. Here, Cullen et al. show that all inflammasome “signal II” agents examined triggered necrosis, with IL-1β secretion confined to necrotic cells, suggesting that IL-1β represents an inducible danger signal.

Description: Publication date: Available online 28 May 2015 Source: Cell Reports Author(s): Bi Zhang , Rui Xiao , Elizabeth A. Ronan , Yongqun He , Ao-Lin Hsu , Jianfeng Liu , X.Z. Shawn Xu Temperature profoundly affects aging in both poikilotherms and homeotherms. A general belief is that lower temperatures extend lifespan, whereas higher temperatures shorten it. Although this “temperature law” is widely accepted, it has not been extensively tested. Here, we systematically evaluated the role of temperature in lifespan regulation in C. elegans . We found that, although exposure to low temperatures at the adult stage prolongs lifespan, low-temperature treatment at the larval stage surprisingly reduces lifespan. Interestingly, this differential effect of temperature on longevity in larvae and adults is mediated by the same thermosensitive TRP channel TRPA-1 that signals to the transcription factor DAF-16/FOXO. DAF-16/FOXO and TRPA-1 act in larva to shorten lifespan but extend lifespan in adulthood. DAF-16/FOXO differentially regulates gene expression in larva and adult in a temperature-dependent manner. Our results uncover complexity underlying temperature modulation of longevity, demonstrating that temperature differentially regulates lifespan at different stages of life. Graphical abstract Teaser Zhang et al. show that, although exposure of C. elegans to low temperatures during adulthood prolongs lifespan, low-temperature treatment during development reduces lifespan. This differential temperature effect is mediated by the thermosensitive channel TRPA-1.

Description: Publication date: Available online 28 May 2015 Source: Cell Reports Author(s): Sumeda Nandadasa , Courtney M. Nelson , Suneel S. Apte Despite the significance for fetal nourishment in mammals, mechanisms of umbilical cord vascular growth remain poorly understood. Here, the secreted metalloprotease ADAMTS9 is shown to be necessary for murine umbilical cord vascular development. Restricting it to the cell surface using a gene trap allele, Adamts9 Gt , impaired umbilical vessel elongation and radial growth via reduced versican proteolysis and accumulation of extracellular matrix (ECM). Both Adamts9 Gt and conditional Adamts9 deletion revealed that ADAMTS9 produced by mesenchymal cells acted non-autonomously to regulate smooth muscle cell (SMC) proliferation, differentiation, and orthogonal reorientation during growth of the umbilical vasculature. In Adamts9 Gt/Gt , we observed interference with PDGFRβ signaling via the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway, which regulates cytoskeletal dynamics during SMC rotation. In addition, we observed disrupted Shh signaling and perturbed orientation of the mesenchymal primary cilium. Thus, ECM dynamics is a major influence on umbilical vascular SMC fate, with ADAMTS9 acting as its principal mediator. Graphical abstract Teaser Nandadasa et al. show that ADAMTS9, a secreted metalloprotease, is essential for versican proteolysis during mouse umbilical cord vascular development. In an Adamts9 gene trap mutant, they report non-autonomous impairment of crucial steps in smooth muscle signaling pathways and differentiation that are essential for construction of the umbilical vessel wall.

Description: Publication date: Available online 28 May 2015 Source: Cell Reports Author(s): Jörg Waldhaus , Robert Durruthy-Durruthy , Stefan Heller The organ of Corti harbors highly specialized sensory hair cells and surrounding supporting cells that are essential for the sense of hearing. Here, we report a single cell gene expression data analysis and visualization strategy that allows for the construction of a quantitative spatial map of the neonatal organ of Corti along its major anatomical axes. The map displays gene expression levels of 192 genes for all organ of Corti cell types ordered along the apex-to-base axis of the cochlea. Statistical interrogation of cell-type-specific gene expression patterns along the longitudinal gradient revealed features of apical supporting cells indicative of a propensity for proliferative hair cell regeneration. This includes reduced expression of Notch effectors, receptivity for canonical Wnt signaling, and prominent expression of early cell-cycle genes. Cochlear hair cells displayed expression gradients of genes indicative of cellular differentiation and the establishment of the tonotopic axis. Graphical abstract Teaser Waldhaus et al. reconstruct a spatial 2D map of the organ of Corti from single cell gene expression profiles. Statistical interrogation of cell-type-specific gene expression along the map reveals expression gradients and provides a tool to integrate functional data with complex gene expression patterns.

Description: Publication date: Available online 11 June 2015 Source: Cell Reports Author(s): Simon M.G. Braun , Gregor-Alexander Pilz , Raquel A.C. Machado , Jonathan Moss , Burkhard Becher , Nicolas Toni , Sebastian Jessberger Demyelinating diseases are characterized by a loss of oligodendrocytes leading to axonal degeneration and impaired brain function. Current strategies used for the treatment of demyelinating disease such as multiple sclerosis largely rely on modulation of the immune system. Only limited treatment options are available for treating the later stages of the disease, and these treatments require regenerative therapies to ameliorate the consequences of oligodendrocyte loss and axonal impairment. Directed differentiation of adult hippocampal neural stem/progenitor cells (NSPCs) into oligodendrocytes may represent an endogenous source of glial cells for cell-replacement strategies aiming to treat demyelinating disease. Here, we show that Ascl1-mediated conversion of hippocampal NSPCs into mature oligodendrocytes enhances remyelination in a diphtheria-toxin (DT)-inducible, genetic model for demyelination. These findings highlight the potential of targeting hippocampal NSPCs for the treatment of demyelinated lesions in the adult brain. Graphical abstract Teaser Regenerative approaches for replacing lost oligodendrocytes in demyelinating disease are scant. Braun et al. show that programming adult hippocampal neural stem/progenitor cells (NSPCs) into oligodendrocytes enhances remyelination in a genetic model of demyelination, highlighting the potential of targeting hippocampal NSPCs for the treatment of demyelinated lesions.

Description: Publication date: Available online 11 June 2015 Source: Cell Reports Author(s): Vitor Fortuna , Luc Pardanaud , Isabelle Brunet , Roxana Ola , Emma Ristori , Massimo M. Santoro , Stefania Nicoli , Anne Eichmann The sympathetic nervous system controls smooth muscle tone and heart rate in the cardiovascular system. Postganglionic sympathetic neurons (SNs) develop in close proximity to the dorsal aorta (DA) and innervate visceral smooth muscle targets. Here, we use the zebrafish embryo to ask whether the DA is required for SN development. We show that noradrenergic (NA) differentiation of SN precursors temporally coincides with vascular mural cell (VMC) recruitment to the DA and vascular maturation. Blocking vascular maturation inhibits VMC recruitment and blocks NA differentiation of SN precursors. Inhibition of platelet-derived growth factor receptor (PDGFR) signaling prevents VMC differentiation and also blocks NA differentiation of SN precursors. NA differentiation is normal in cloche mutants that are devoid of endothelial cells but have VMCs. Thus, PDGFR-mediated mural cell recruitment mediates neurovascular interactions between the aorta and sympathetic precursors and promotes their noradrenergic differentiation. Graphical abstract Teaser Fortuna et al. show that neurovascular interactions between the aorta and sympathetic precursors are mediated by PDGFR-driven mural cell recruitment that promotes noradrenergic differentiation.

Description: Publication date: Available online 11 June 2015 Source: Cell Reports Author(s): Lingfeng Meng , Ben Mulcahy , Steven J. Cook , Marianna Neubauer , Airong Wan , Yishi Jin , Dong Yan Synapse elimination occurs in development, plasticity, and disease. Although the importance of synapse elimination has been documented in many studies, the molecular mechanisms underlying this process are unclear. Here, using the development of C. elegans RME neurons as a model, we have uncovered a function for the apoptosis pathway in synapse elimination. We find that the conserved apoptotic cell death (CED) pathway and axonal mitochondria are required for the elimination of transiently formed clusters of presynaptic components in RME neurons. This function of the CED pathway involves the activation of the actin-filament-severing protein, GSNL-1. Furthermore, we show that caspase CED-3 cleaves GSNL-1 at a conserved C-terminal region and that the cleaved active form of GSNL-1 promotes its actin-severing ability. Our data suggest that activation of the CED pathway contributes to selective elimination of synapses through disassembly of the actin filament network. Graphical abstract Teaser Meng et al. find that activation of the cell death pathway in C. elegans neurons contributes to selective elimination of synapses through disassembly of the actin filament network.

Description: Publication date: Available online 11 June 2015 Source: Cell Reports Author(s): Bettina Drisaldi , Luca Colnaghi , Luana Fioriti , Nishta Rao , Cory Myers , Anna M. Snyder , Daniel J. Metzger , Jenna Tarasoff , Edward Konstantinov , Paul E. Fraser , James L. Manley , Eric R. Kandel Protein synthesis is crucial for the maintenance of long-term-memory-related synaptic plasticity. The prion-like cytoplasmic polyadenylation element-binding protein 3 (CPEB3) regulates the translation of several mRNAs important for long-term synaptic plasticity in the hippocampus. Here, we provide evidence that the prion-like aggregation and activity of CPEB3 is controlled by SUMOylation. In the basal state, CPEB3 is a repressor and is soluble. Under these circumstances, CPEB3 is SUMOylated in hippocampal neurons both in vitro and in vivo. Following neuronal stimulation, CPEB3 is converted into an active form that promotes the translation of target mRNAs, and this is associated with a decrease of SUMOylation and an increase of aggregation. A chimeric CPEB3 protein fused to SUMO cannot form aggregates and cannot activate the translation of target mRNAs. These findings suggest a model whereby SUMO regulates translation of mRNAs and structural synaptic plasticity by modulating the aggregation of the prion-like protein CPEB3. Graphical abstract Teaser Drisaldi et al. argue that, under basal, unstimulated conditions, CPEB3 is SUMOylated and mostly soluble. After neuronal stimulation, CPEB3 becomes deSUMOylated and more aggregated. DeSUMOylation and aggregation are two crucial steps required for the translation of the mRNA targets of CPEB3 and for dendritic filopodia formation.

Description: Publication date: Available online 11 June 2015 Source: Cell Reports Author(s): Eric M. Davis , Jihye Kim , Bridget L. Menasche , Jacob Sheppard , Xuedong Liu , Aik-Choon Tan , Jingshi Shen Glycophosphatidylinositol-anchored proteins (GPI-APs) play essential roles in physiology, but their biogenesis and trafficking have not been systematically characterized. Here, we took advantage of the recently available haploid genetics approach to dissect GPI-AP pathways in human cells using prion protein (PrP) and CD59 as model molecules. Our screens recovered a large number of common and unexpectedly specialized factors in the GPI-AP pathways. PIGN , PGAP2 , and PIGF , which encode GPI anchor-modifying enzymes, were selectively isolated in the CD59 screen, suggesting that GPI anchor composition significantly influences the biogenesis of GPI-APs in a substrate-dependent manner. SEC62 and SEC63 , which encode components of the ER-targeting machinery, were selectively recovered in the PrP screen, indicating that they do not constitute a universal route for the biogenesis of mammalian GPI-APs. Together, these comparative haploid genetic screens demonstrate that, despite their similarity in overall architecture and subcellular localization, GPI-APs follow markedly distinct biosynthetic and trafficking pathways. Graphical abstract Teaser Using comparative haploid genetic screens in human cells, Davis et al. find that GPI-anchored proteins follow markedly distinct biosynthetic and trafficking pathways in spite of their similarity in overall architecture and subcellular localization.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.

Description: 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.