ALBERT

Description: The Miocene expansion of C4 plants (mainly tropical grasses) between 8 and 4 million years (Ma) remains an enigma since regional differences in the timing of the expansion rules out decreased CO2 (pCO2) as a dominant forcing [e.g. Tipple and Pagani, 2007. The early origins of terrestrial C4 photosynthesis. Annu. Rev. Earth Planet. Sci. 35, 435–461]. Other environmental factors, such as low-latitude aridity and seasonality have been proposed to explain the low tree versus grass ratio found in savannahs and tropical grasslands of the world, but conclusive evidence is missing. Here we use pollen and stable carbon (δ13C) and hydrogen (δD) isotope ratios of terrestrial plant wax from a South Atlantic sediment core (ODP Site 1085) to reconstruct Miocene to Pliocene changes of vegetation and rainfall regime of western southern Africa. Our results reveal changes in the relative amount of precipitation and indicate a shift of the main moisture source from the Atlantic to the Indian Ocean during the onset of a major aridification 8 Ma ago. We emphasize the importance of declining precipitation during the expansion of C4 and CAM (mainly succulent) vegetation in South Africa. We suggest that the C4 plant expansion resulted from an increased equator-pole temperature gradient caused by the initiation of strong Atlantic Meridional Overturning Circulation following the shoaling of the Central American Seaway during the Late Miocene.

Description: Linear Pottery Culture (LBK) are investigated. These are interpreted as resulting from a combination of internal socio-economic processes as well as external environmental parameters. Resilience theory is helpful in understanding periods of increased vulnerability and inherent trends to social complexity. Cycles and threshold levels also help to understand why societies experience periods of increasing fragility and subsequent decline. Results are based on the correlation of a typology and dendrochronology-based archaeological chronology for western LBK and various palaeoclimatic proxy-data. The 14C-production curve is taken as an indicator for solar activity fluctuations, and an age model for laminated sediments as an indicator for rainfall fluctuations. We currently consider this correlation as agreeably robust; however future finedating may result in slight shifts within the archaeological chronology. According to the applied age model, the simple farming societies of the LBK (5600e4900 cal BC) in west-central Europe were not immediately and devastatingly affected by most climate fluctuations. Yet, they might have been one destabilising component within broader processes. However, periods of decreased or irregularly spaced rainfall are contemporaneous to periods of population decline, while periods of increased rainfall may have favoured population growth. Towards the end of the 6th millennium cal BC, the final years of LBK in western Central Europe are contemporaneous to a general trend to less rainfall punctuated by short-term increases in precipitation. During this climatically highly volatile period LBK reaches its highest population rates and at the same time experiences a period of warfare. Thereafter population rates decline and LBK gradually vanishes from the archaeological record, being replaced by Middle Neolithic societies.

Description: Co-injection of a conservative tracer during the geological sequestration of CO2 can imprint a marker to the injected gas that can be easily recognized during soil gas surveys in case of CO2 leakage from the reservoir toward the surface. In this work, an ultra-trace detection method, based on gas chromatography with electron capture detection for analyzing perfluorocarbon tracers (PFTs) in soil gas samples was optimized. Three totally fluorinated cycloalcane compounds consisting of five and six atom carbon rings were selected for this purpose. We evaluated the feasibility of collecting PFTs on adsorbent tube packed with a commercial graphitized carbon black (Carbotrap™ 100) sampling 2 L of soil gas. The sorbent tubes were then analyzed by using a two-stage thermal desorption process. The developed method allows to quickly determine these compounds at very low fL/L level, method identification limits ranged from 1.3 to 5.8 fL/L. Moreover, it shows good precision, evaluated by within-day and between-day studies. A preliminary survey of the PFT soil gas background concentrations, conducted by analyzing some soil gas samples collected in two different areas in Central Italy and in the Po Plain, ascertained the PFT background concentration lower than MIL.

Description: Published

Description: 60-64

Description: 2.4. TTC - Laboratori di geochimica dei fluidi

Description: JCR Journal

Description: partially_open

Description: Repeating volcano-tectonic (VT) earthquakes, taking place at Mt. Etna during 1999–2009,were detected and analyzed to investigate their behavior. We found 735 families amounting to 2479 VT earthquakes, representing ~38% of all the analyzed VT earthquakes. The number of VT earthquakes making up the families ranges from 2 to 23. Over 70% of the families comprise 2 or 3 VT earthquakes and only 20 families by more than 10 events. The occurrence lifetime is also highly variable ranging from some minutes to ten years. In particular, more than half of the families have a lifetime shorter than 0.5 day and only ~10% longer than 1 year. On the basis of these results, most of the detected families were considered “burst-type”, i.e., show swarm-like occurrence, and hence their origin cannot be explained by a temporally constant tectonic loading. Indeed, since the analyzed earthquakes take place in a volcanic area, the rocks are affected not only by tectonic stresses related to the fairly steady regional stress field but also by local stresses, caused by the volcano, such as magma batch intrusions/ movements and gravitational loading.We focused on the five groups of families characterized by the longest repeatability over time, namely high number of events and long lifetime, located in the north-eastern, eastern and southern flanks of the volcano. Unlike the first four groups, which similarly to most of the detected families show swarm-like VT occurrences, group “v”, located in the north-eastern sector, exhibits a more “tectonic” behavior with the events making up such a group spread over almost the entire analyzed period. It is clear how both occurrence and slip rates do not remain constant but vary over time, and such changes are time-related to the occurrence of the 2002–2003 eruption. Finally, by FPFIT algorithm a good agreement between directions identified by nodal planes and the earthquake epicentral distribution was generally found.

Description: Published

Description: 1223 – 1236

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: JCR Journal

Description: restricted

Description: The Geochemical Monitoring System II (GMSII)prototype was designed, assembled, tested and installed at the Acqua Difesa test site, near Belpasso (Catania).

Description: Published

Description: 273-306

Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani

Description: JCR Journal

Description: restricted

Description: Syngenetically frozen deposits that are fine-grained and ice-rich are widely distributed in lowlands of northeastern Siberia, Alaska and northwestern Canada. These late Pleistocene sediments are specific to this region summarized as Beringia, and have been termed 'Ice Complex' or 'Yedoma' in Siberia, and 'muck' in North America. Silt is their dominant material, but they also include abundant organic matter preserved in permafrost since the time of deposition. Vegetation and faunal reconstructions indicate that the sediments aggraded largely under a cryoxeric environment characterized by graminoid and forb-rich vegetation that supported a grazing megafauna population during the Pleistocene.

Description: Abstract Research investigating the genetic basis of physiological responses has significantly broadened our understanding of the mechanisms underlying organismic response to environmental change. However, genomic data are currently available for few taxa only, thus excluding physiological model species from this approach. In this study we report the transcriptome of the model organism Hyas araneus from Spitsbergen (Arctic). We generated 20,479 transcripts, using the 454 {GS} {FLX} sequencing technology in combination with an Illumina HiSeq sequencing approach. Annotation by Blastx revealed 7159 blast hits in the {NCBI} non-redundant protein database. The comparison between the spider crab H. araneus transcriptome and {EST} libraries of the European lobster Homarus americanus and the porcelain crab Petrolisthes cinctipes yielded 3229/2581 sequences with a significant hit, respectively. The clustering by the Markov Clustering Algorithm (MCL) revealed a common core of 1710 clusters present in all three species and 5903 unique clusters for H. araneus. The combined sequencing approaches generated transcripts that will greatly expand the limited genomic data available for crustaceans. We introduce the {MCL} clustering for transcriptome comparisons as a simple approach to estimate similarities between transcriptomic libraries of different size and quality and to analyze homologies within the selected group of species. In particular, we identified a large variety of reverse transcriptase (RT) sequences not only in the H. araneus transcriptome and other decapod crustaceans, but also sea urchin, supporting the hypothesis of a heritable, anti-viral immunity and the proposed viral fragment integration by host-derived {RTs} in marine invertebrates.

Description: Coastal upwelling ecosystems are areas of high productivity and strong outgassing, where most gases, such as N2O and CH4, are produced in subsurface waters by anaerobic metabolisms. We describe seasonal CH4 variation as well as potential mechanisms producing CH4 in surface waters of the central Chile upwelling ecosystem (36°S). Surface waters were always supersaturated in CH4 (from 125% up to 550%), showing a clear seasonal signal triggered by wind driven upwelling processes (austral spring– summer period), that matched with the periods of high chlorophyll-a and dimethylsulfoniopropionate (DMSP) levels. Methane cycling experiments, with/without the addition of dimethylsulfide (including 13C-DMS) and acetylene (a nonspecific inhibitor of CH4 oxidation) along with monthly measurements of CH4, DMSP and other oceanographic variables revealed that DMS can be a CH4 precursor. Net CH4 cycling rates (control) fluctuated between -0.64 and 1.44 nmol L-1 d-1. After the addition of acetylene, CH4 cycling rates almost duplicated relative to the control, suggesting a strong methanotrophic activity. With a spike of DMS, the net CH4 cycling rate significantly increased relative to the acetylene and control treatment. Additionally, the d13C values of CH4 at the end of the incubations (after addition of 13C enriched-DMS) were changed, reaching -32‰ PDB compared to natural values between -44‰ and -46‰ PDB. These findings indicate that, in spite of the strong CH4 consumption by methanotrophs, this upwelling area is an important source of CH4 to the atmosphere. The effluxes are derived partially from in situ surface production and seem to be related to DMSP/DMS metabolism.

Description: Abstract Radiocarbon and uranium-thorium dating results are presented from a genus of calcitic Antarctic cold-water octocorals (family Coralliidae), which were collected from the Marie Byrd Seamounts in the Amundsen Sea (Pacific sector of the Southern Ocean) and which to date have not been investigated geochemically. The geochronological results are set in context with solution and laser ablation-based element/Ca ratios (Li, B, Mg, Mn, Sr, Ba, U, Th). Octocoral radiocarbon ages on living corals are in excellent agreement with modern ambient deep-water �14C, while multiple samples of individual fossil coral specimens yielded reproducible radiocarbon ages. Provided that local radiocarbon reservoir ages can be derived for a given time, fossil Amundsen Sea octocorals should be reliably dateable by means of radiocarbon. In contrast to the encouraging radiocarbon findings, the uranium-series data are more difficult to interpret. The uranium concentration of these calcitic octocorals is an order of magnitude lower than in the aragonitic hexacorals that are conventionally used for geochronological investigations. While modern and Late Holocene octocorals yield initial δ234U in good agreement with modern seawater, our results reveal preferential inward diffusion of dissolved alpha-recoiled 234U and its impact on fossil coral δ234U. Besides alpha-recoil related 234U diffusion, high-resolution sampling of two fossil octocorals further demonstrates that diagenetic uranium mobility has offset apparent coral U-series ages. Combined with the preferential alpha-recoil 234U diffusion, this process has prevented fossil octocorals from preserving a closed system U-series calendar age for longer than a few thousand years. Moreover, several corals investigated contain significant initial thorium, which cannot be adequately corrected for because of an apparently variable initial 232Th/230Th. Our results demonstrate that calcitic cold-water corals are unsuitable for reliable U-series dating. Mg/Ca ratios within single octocoral specimens are internally strikingly homogeneous, and appear promising in terms of their response to ambient temperature. Magnesium/lithium ratios are significantly higher than usually observed in other deep marine calcifiers and for many of our studied corals are remarkably close to seawater compositions. Although this family of octocorals is unsuitable for glacial deep-water �14C reconstructions, our findings highlight some important differences between hexacoral (aragonitic) and octocoral (calcitic) biomineralisation. Calcitic octocorals could still be useful for trace element and some isotopic studies, such as reconstruction of ambient deep water neodymium isotope composition or pH, via boron isotopic measurements.

Description: The AND-1B drill core (1285 m-long) was recovered, inside the ANDRILL (ANtarctic geological DRILLing) Program, during the austral summer of 2006/07 from beneath the floating McMurdo Ice Shelf. Drilling recovered a stratigraphic succession of alternating diamictites, diatomites and volcaniclastic sediments spanning about the last 14 Ma. A core portion between 350 and 480 mbsf, including a 80 m-thick diatomite interval recording the early Pliocene warming event, was investigated in term of opal biogenic content and element geochemistry. Across the diatomite interval, in spite of the lithological uniformity, a fluctuating biogenic opal profile mirrors the δ18O record, testifying a decrease in productivity when temperature drops as a consequence of small glacial fluctuations. The comparison of biogenic opal data with Chaetoceros spp. abundances from Konfirst et al. (2012) documents alternations between periods of high primary productivity in stratified surface waters and of enhanced terrigenous input in ice-free conditions. Cluster analysis discriminates elements associated to terrigenous input from those subject to biogenic control. Further separation in sub-cluster was interpreted in term of different element response to changes in provenance but also to depositional/early diagenetic conditions at the seafloor. Whilst K and Ti are related to different sediment sources confirming previous studies from the same interval, V, Zn and, to a lesser extent, Fe, document reducing/anoxic conditions during the diatomites deposition (in particular in 400–460 mbsf interval). Mg, Sr and Mn contents are related to authigenic carbonate precipitation whilst Ba is interested by nonsteady-state processes leading to local peaks of barium below the sulphate-rich/sulphate-poor pore water boundary where generally the low degree of barite saturation is responsible for Ba remobilization. Such alteration in depositional dynamics, responsible of the precipitation of an oxygen-depleted barium phase, was probably induced by change in sedimentation rate and/or in palaeoenvironmental conditions.

Description: In recent years, a novel proxy for the past occurrence of Arctic sea ice has been proposed that is based on the variable marine sedimentary abundance of an organic geochemical lipid derived from sea ice diatoms in the spring. This lipid, termed IP25 (Ice Proxy with 25 carbon atoms), is a highly branched isoprenoid mono-unsaturated alkene that appears to be sufficiently stable in sediments to permit meaningful palaeo sea ice reconstructions to be carried out over short- to long-term timescales. Since the first proposed use of IP25 as a proxy for palaeo sea ice by Belt et al. (2007), a number of laboratories have measured this biomarker in Arctic sediments and it is anticipated that research activity in this area will increase further in the future. The content of this review is divided into a number of sections. Firstly, we describe the scientific basis for the IP25 proxy and its initial discovery in Arctic sea ice, sedimenting particles and sediments. Secondly, we summarise the relatively few studies that have, to date, concentrated on examining the factors that influence the production and fate of IP25 and we identify some areas of future research that need to be addressed in order to improve our understanding of IP25 data obtained from sedimentary analyses. What is clear at this stage, however, it that the presence of IP25 in Arctic marine sediments appears to represent a proxy measure of past seasonal sea ice rather than permanent or multi-year ice conditions. Thirdly, we highlight the importance of rigorous analytical identification and quantification of IP25, especially if measurements of this biomarker are going to be used for quantitative sea ice reconstructions, rather than qualitative analyses alone (presence/absence). Fourthly, we review some recent attempts to make the interpretations of IP25 biomarker data more detailed and quantitative by combining sedimentary abundances with those of phytoplankton- and other sea ice-derived biomarkers. Thus, the bases for the so-called PIP25 and DIP25 indices are described, together with an overview of potential limitations, concluding that investigations into the use of these indices needs further research before their full potential can be realised. In the final section, we provide a summary of IP25-based palaeo sea ice reconstruction case studies performed to date. These case studies cover different Arctic regions and timescales spanning decades to tens of thousands of years.

Description: Cratons with their thick lithospheric roots can influence the thermal structure, and thus the convective flow, in the surrounding mantle. As mantle temperatures are hard to measure directly, depth variations in the mantle transition zone (MTZ) discontinuities are often employed as a proxy. Here, we use a large new data set of P-receiver functions to map the 410 km and 660 km discontinuities beneath the western edge of the East European Craton and adjacent Phanerozoic Europe across the most fundamental lithospheric boundary in Europe, the Trans-European Suture Zone (TESZ). We observe significantly shorter travel times for conversions from both MTZ discontinuities within the craton, caused by the high velocities of the cratonic root. By contrast, the differential travel time across the MTZ is normal to only slightly raised. This implies that any insulating effect of the cratonic keel does not reach the MTZ. In contrast to earlier observations in Siberia, we do not find any trace of a discontinuity at 520 km depth, which indicates a rather dry MTZ beneath the western edge of the craton. Within most of covered Phanerozoic Europe, the MTZ differential travel time is remarkably uniform and in agreement with standard Earth models. No widespread thermal effects of the various episodes of Caledonian and Variscan subduction that took place during the amalgamation of the continent remain. Only more recent tectonic events, related to Alpine subduction and Quarternary volcanism in the Eifel area, can be traced. While the East European craton shows no distinct imprint into the MTZ, we discover the signature of the TESZ in the MTZ in the form of a linear region of about 350 km width with a 1.5 s increase in differential travel time, which could either be caused by high water content or decreased temperature. Taking into account results of recent S-wave tomographies, raised water content in the MTZ cannot be the main cause for this observation. Accordingly, we explain the increase, equivalent to a 15 km thicker MTZ, by a temperature decrease of about 80 K. We discuss two alternative models for this temperature reduction, either a remnant of subduction or an indication of downwelling due to small-scale, edge-driven convection caused by the contrast in lithospheric thickness across the TESZ. Any subducted lithosphere found in the MTZ at this location is unlikely to be related to Variscan subduction along the TESZ, though, as Eurasia has moved significantly northward since the Variscan orogeny.

Description: We use a 27 year long time series of repeated transient tracer observations to investigate the evolution of the ventilation timescales and the related content of anthropogenic carbon(Cant) in deep and bottom water in the Weddell Sea. This time series consists of chlorofluorocarbon (CFC) observations from 1984 to 2008 together with first combined CFC and sulphurhexafluoride (SF6) measurements from 2010/2011 along the Prime Meridian in the Antarctic Ocean and across the Weddell Sea. Applying the Transit Time Distribution (TTD) method we find that all deep water masses in the Weddell Sea have been continually growing older and getting less ventilated during the last 27years. The decline of the ventilation rate of Weddell Sea Bottom Water (WSBW) and Weddell Sea Deep Water (WSDW) along the Prime Meridian is in the order of 15–21%; the Warm Deep Water (WDW) ventilation rate declined much faster by 33%. About 88–94% of the age increase in WSBW near its source regions (1.8–2.4 years per year) is explained by the age increase of WDW (4.5 years per year). As a consequence of the aging, the Cant increase in the deep and bottom water formed in the Weddell Sea slowed down by 14–21% over the period of observations.

Description: A high input of lithogenic sediment from glaciers was assumed to be responsible for high Fe and Mn contents in the Antarctic soft shell clam Laternula elliptica at King George Island. Indeed, withdrawal experiments indicated a strong influence of environmental Fe concentrations on Fe contents in bivalve hemolymph, but no significant differences in hemolymph and tissue concentrations were found among two sites of high and lower input of lithogenic debris. Comparing Fe and Mn concentrations of porewater, bottom water, and hemolymph from sampling sites, Mn appears to be assimilated as dissolved species, whereas Fe apparently precipitates as ferrihydrite within the oxic sediment or bottom water layer prior to assimilation by the bivalve. Hence, we attribute the high variability of Fe and Mn accumulation in tissues of L. elliptica around Antarctica to differences in the geochemical environment of the sediment and the resulting Fe and Mn flux across the benthic boundary.

Description: Coral recruitment was assessed in highly diverse and economically important Spermonde Archipelago, a reef system subjected to land-based sources of siltation/pollution and destructive fishing, over a period of 2 years. Recruitment on settlement tiles reached up to 705 spat m�2 yr�1 and was strongest in the dry season (July–October), except off-shore, where larvae settled earlier. Pocilloporidae dominated nearshore, while a more diverse community of Acroporidae, Poritidae and others settled in the less polluted mid-shelf and off-shore reefs. Non-coral fouling community appeared to hardly influence initial coral settlement on the tiles, although, this does not necessarily infer low coral post-settlement mortality, which may be enhanced at the near- and off-shore reefs as indicated by increased abundances of potential space competitors on natural substrate. Blast fishing showed no local reduction in coral recruitment and live hard coral cover increased in oligotrophic reefs, indicating potential for coral recovery, if managed effectively.

Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geochimica et Cosmochimica Acta 123 (2013): 322–337, doi:10.1016/j.gca.2013.06.011.

Description: Despite the importance of diatoms in regulating climate and the existence of large opal-containing sediments in key air-ocean exchange areas, most geochemical proxy records are based on carbonates. Among them, Boron (B) content and isotopic composition have been widely used to reconstruct pH from foraminifera and coral fossils. We assessed the possibility of a pH/CO2 seawater concentration control on B content in diatom opal to determine whether or not frustule B concentrations could be used as a pH proxy or to clarify algae physiological responses to acidifying pH. We cultured two well-studied diatom species, Thalassiosira pseudonana and Thalassiosira weissflogii at varying pH conditions and determined Si and C quotas. Frustule B content was measured by both laser-ablation inductively coupled mass spectrometry (LA-ICPMS) and secondary ion mass spectrometry (SIMS/ion probe). For both species, frustules grown at higher pH have higher B contents and higher Si requirements per fixed C. If this trend is representative of diatom silicification in a future more acidic ocean, it could contribute to changes in the efficiency of diatom ballasting and C export, as well as changes in the contribution of diatoms relative to other phytoplankton groups in Si-limited regions. If B enters the cell through the same transporter employed for HCO3− uptake, an increased HCO3− requirement with decreasing CO2 concentrations (higher pH), and higher B(OH)4/HCO3− ratios would explain the observed increase in frustule B content with increasing pH. The mechanism of B transport from the site of uptake to the site of silica deposition is unknown, but may occur via silicon transport vesicles, in which B(OH)4− may be imported for B detoxification and/or as part of a pH regulation strategy either though Na-dependent B(OH)4−/Cl− antiport or B(OH)4−/H+ antiport. B deposition in the silica matrix may occur via substitution of a B(OH)4− for a negatively charged SiO− formed during silicification. With the current analytical precision, B content of frustules is unlikely to resolve ocean pH with a precision of paleoceanographic interest. However, if frustule B content was controlled mainly by HCO3− uptake for photosynthesis, which appears to show a threshold behavior, then measurements of B content might reveal the varying importance of active HCO3− acquisition mechanisms of diatoms in the past.

Description: This work was funded by the European Community under the project ERC-STG-240222-PACE.

Description: Climatic hazards, such as severe droughts and floods, affect extensive areas across monsoon Asia and can have profound impacts on the populations of that region. The area surrounding Indonesia, including large portions of the eastern Indian Ocean and Java Sea, plays a key role in the global climate system because of the enormous heat and moisture exchange that occurs between the ocean and atmosphere there. Here, we evaluate the influence of rainfall variability on multiple tree-ring parameters of teak (Tectona grandis) trees growing in a lowland rain forest in Central Java (Indonesia). We assess the potential of, annually resolved, tree-ring width, stable carbon (δ13C) and oxygen (δ18O) isotope records to improve our understanding of the Asian monsoon variability. Climate response analysis with regional, monthly rainfall data reveals that all three tree-ring parameters are significantly correlated to rainfall, albeit during different monsoon seasons. Precipitation in the beginning of the rainy season (Sep–Nov) is important for tree-ring width, confirming previous studies. Compared to ring width, the stable isotope records possess a higher degree of common signal, especially during portions of the peak rainy season (δ13C: Dec–May; δ18O: Nov–Feb) and are negatively correlated to rainfall. In addition, tree-ring δ18O also responds positively to peak dry season rainfall, although the δ18O rainy season signal is stronger and more time-stable. The correlations of opposite sign reflect the distinct seasonal contrast of the δ18O signatures in rainfall (18OPre) during the dry (18O-enriched rain) and rainy (18O-depleted rain) seasons. This difference in 18OPre signal reflects the combination of two signals in the annual tree-ring δ18O record. Highly resolved intra-annual δ18O isotope analyses suggest that the signals of dry and rainy season can be distinguished clearly. Thereby reconstructions can improve our understanding of variations and trends of the hydrological cycle over the Indonesian archipelago.

Description: This study presents a reconstruction of the Late Holocene climate in Kamchatka based on chironomid remains from a 332 cm long composite sediment core recovered from Dvuyurtochnoe Lake (Two-Yurts Lake, TYL) in central Kamchatka. The oldest recovered sediments date to about 4500 cal years BP. Chironomid head capsules from TYL reflect a rich and diverse fauna. An unknown morphotype of Tanytarsini, Tanytarsus type klein, was found in the lake sediments. Our analysis reveals four chironomid assemblage zones reflecting four different climatic periods in the Late Holocene. Between 4500 and 4000 cal years BP, the chironomid composition indicates a high lake level, well-oxygenated lake water conditions and close to modern temperatures (w13 �C). From 4000 to 1000 cal years BP, two consecutive warm intervals were recorded, with the highest reconstructed temperature reaching 16.8 �C between 3700 and 2800 cal years BP. Cooling trend, started around 1100 cal years BP led to low temperatures during the last stage of the Holocene. Comparison with other regional studies has shown that termination of cooling at the beginning of late Holocene is relatively synchronous in central Kamchatka, South Kurile, Bering and Japanese Islands and take place around 3700 cal years BP. From ca 3700 cal years BP to the last millennium, a newly strengthened climate continentality accompanied by general warming trend with minor cool excursions led to apparent spatial heterogeneity of climatic patterns in the region. Some timing differences in climatic changes reconstructed from chironomid record of TYL sediments and late Holocene events reconstructed from other sites and other proxies might be linked to differences in local forcing mechanisms or caused by the different degree of dating precision, the different temporal resolution, and the different sensitive responses of climate proxies to the climate variations. Further high-resolution stratigraphic studies in this region are needed to understand the spatially complex pattern of climate change in Holocene in Kamchatka and the surrounding region. �

Description: Publication date: Available online 7 September 2013 Source: FEBS Open Bio Author(s): Veronika Temml , Susanne Kuehnl , Daniela Schuster , Stefan Schwaiger , Hermann Stuppner , Dietmar Fuchs Mediterranean Carthamus tinctorius (Safflower) is used for treatment of inflammatory conditions and neuropsychiatric disorders. Recently C. tinctorius lignans arctigenin and trachelogenin but not matairesinol were described to interfere with the activity of tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) in peripheral blood mononuclear cells in vitro . We examined a potential direct influence of compounds on IDO enzyme activity applying computational calculations based on 3D geometry of the compounds. The interaction pattern analysis and force field-based minimization was performed within LigandScout 3.03, the docking simulation with MOE 2011.10 using the X-ray crystal structure of IDO. Results confirm the possibility of an intense interaction of arctigenin and trachelogenin with the binding site of the enzyme, while matairesinol had no such effect.

Description: Publication date: Available online 7 September 2013 Source: FEBS Open Bio Author(s): Mitsuru Ishikawa , Jun Shiota , Yuta Ishibashi , Tomoyuki Hakamata , Shizuku Shoji , Mamoru Fukuchi , Masaaki Tsuda , Tomoaki Shirao , Yuko Sekino , Toshihisa Ohtsuka , Jay M. Baraban , Akiko Tabuchi Megakaryoblastic leukemia 1 (MKL1) is a member of the MKL family of serum response factor (SRF) coactivators. Here we have identified three rat MKL1 transcripts: two are homologues of mouse MKL1 transcripts, full-length MKL1 (FLMKL1) and basic, SAP, and coiled-coil domains (BSAC), the third is a novel transcript, M KL1- elo ngated d erivative of y ield (MELODY). These rat MKL1 transcripts are differentially expressed in a wide variety of tissues with highest levels in testis and brain. During brain development, these transcripts display differential patterns of expression. The FLMKL1 transcript encodes two isoforms that utilize distinct translation start sites. The longer form possesses three actin-binding RPXXXEL (RPEL) motifs and the shorter form, MKL1met only has two RPEL motifs. All four rat MKL1 isoforms, FLMKL1, BSAC, MKL1met and MELODY increased SRF-mediated transcription, but not CREB-mediated transcription. Accordingly, the differential expression of MKL1 isoforms may help fine-tune gene expression during brain development.

Description: Publication date: Available online 11 September 2013 Source: FEBS Open Bio Author(s): Gisele Castro , Maria Fernanda C. Areias , Lais Weissmann , Paula G.F. Quaresma , Carlos K. Katashima , Mario J.A. Saad , Patricia O. Prada Insulin acts in the hypothalamus, decreasing food intake (FI) by the IR/PI3K/Akt pathway. This pathway is impaired in obese animals and endoplasmic reticulum (ER) stress and low-grade inflammation are possible mechanisms involved in this impairment. Here, we highlighted the amygdala as an important brain region for FI regulation in response to insulin. This regulation was dependent on PI3K/AKT pathway similar to the hypothalamus. Insulin was able to decrease neuropeptide Y (NPY) and increase oxytocin mRNA levels in the amygdala via PI3K, which may contribute to hypophagia. Additionally, obese rats did not reduce FI in response to insulin and AKT phosphorylation was decreased in the amygdala, suggesting insulin resistance. Insulin resistance was associated with ER stress and low-grade inflammation in this brain region. The inhibition of ER stress with PBA reverses insulin action/signaling, decreases NPY and increases oxytocin mRNA levels in the amygdala from obese rats, suggesting that ER stress is probably one of the mechanisms that induce insulin resistance in the amygdala.

Description: Publication date: Available online 12 September 2013 Source: Cell Reports Author(s): Debra A. Mayes , Tilat A. Rizvi , Haley Titus-Mitchell , Rachel Oberst , Georgianne M. Ciraolo , Charles V. Vorhees , Andrew P. Robinson , Stephen D. Miller , Jose A. Cancelas , Anat O. Stemmer-Rachamimov , Nancy Ratner Patients with neurofibromatosis type 1 (NF1) and Costello syndrome Rasopathy have behavioral deficits. In NF1 patients, these may correlate with white matter enlargement and aberrant myelin. To model these features, we induced Nf1 loss or HRas hyperactivation in mouse oligodendrocytes. Enlarged brain white matter tracts correlated with myelin decompaction, downregulation of claudin-11, and mislocalization of connexin-32. Surprisingly, non-cell-autonomous defects in perivascular astrocytes and the blood-brain barrier (BBB) developed, implicating a soluble mediator. Nitric oxide (NO) can disrupt tight junctions and gap junctions, and NO and NO synthases (NOS1–NOS3) were upregulated in mutant white matter. Treating mice with the NOS inhibitor NG-nitro-L-arginine methyl ester or the antioxidant N-acetyl cysteine corrected cellular phenotypes. CNP-HRasG12V mice also displayed locomotor hyperactivity, which could be rescued by antioxidant treatment. We conclude that Nf1/Ras regulates oligodendrocyte NOS and that dysregulated NO signaling in oligodendrocytes can alter the surrounding vasculature. The data suggest that antioxidants may improve some behavioral deficits in Rasopathy patients. Graphical abstract Teaser In this study, Ratner and colleagues show that altering intracellular signaling in oligodendrocytes affects brain astrocytes and blood vessels that together make up the blood-brain barrier. Increasing oligodendrocyte Ras-GTP, mimicking neurofibromatosis type 1 and Costello syndrome, disrupted astrocyte and endothelial cell tight junctions and gap junctions and caused a leaky blood-brain barrier. Exposure to a nitric oxide synthase inhibitor or an antioxidant reversed cellular phenotypes and behavioral hyperactivity. Thus, oligodendrocytes contribute to brain homeostasis, and antioxidant therapy may be beneficial when homeostasis is disrupted.

Description: Publication date: Available online 12 September 2013 Source: Cell Reports Author(s): Dalit Ben-Yosef , Francesca S. Boscolo , Hadar Amir , Mira Malcov , Ami Amit , Louise C. Laurent Given the association between mutational load and cancer, the observation that genetic aberrations are frequently found in human pluripotent stem cells (hPSCs) is of concern. Prior studies in human induced pluripotent stem cells (hiPSCs) have shown that deletions and regions of loss of heterozygosity (LOH) tend to arise during reprogramming and early culture, whereas duplications more frequently occur during long-term culture. For the corresponding experiments in human embryonic stem cells (hESCs), we studied two sets of hESC lines: one including the corresponding parental DNA and the other generated from single blastomeres from four sibling embryos. Here, we show that genetic aberrations observed in hESCs can originate during preimplantation embryo development and/or early derivation. These early aberrations are mainly deletions and LOH, whereas aberrations arising during long-term culture of hESCs are more frequently duplications. Our results highlight the importance of close monitoring of genomic integrity and the development of improved methods for derivation and culture of hPSCs. Graphical abstract Teaser Human embryonic stem cells (hESCs) are potential sources of cells for transplantation therapy. However, given the association between mutations and cancer, the frequency of genetic aberrations observed in hESCs is concerning. Using unique pedigrees of hESC lines, Laurent and colleagues now find that aberrations that occur during cell-line derivation are mainly deletions and loss of heterozygosity, whereas duplications arise more commonly during long-term culture. These results highlight the need for improved methods for derivation and culture that preserve the genetic integrity of hESCs.

Description: Publication date: Available online 12 September 2013 Source: Cell Reports Author(s): Jason Karpac , Benoit Biteau , Heinrich Jasper Loss of metabolic homeostasis is a hallmark of aging and is commonly characterized by the deregulation of adaptive signaling interactions that coordinate energy metabolism with dietary changes. The mechanisms driving age-related changes in these adaptive responses remain unclear. Here, we characterize the deregulation of an adaptive metabolic response and the development of metabolic dysfunction in the aging intestine of Drosophila . We find that activation of the insulin-responsive transcription factor Foxo in intestinal enterocytes is required to inhibit the expression of evolutionarily conserved lipases as part of a metabolic response to dietary changes. This adaptive mechanism becomes chronically activated in the aging intestine, mediated by changes in Jun-N-terminal kinase (JNK) signaling. Age-related chronic JNK/Foxo activation in enterocytes is deleterious, leading to sustained repression of intestinal lipase expression and the disruption of lipid homeostasis. Changes in the regulation of Foxo-mediated adaptive responses thus contribute to the age-associated breakdown of metabolic homeostasis. Graphical abstract Teaser Aging is associated with a loss of metabolic homeostasis, which is a risk factor for various human pathologies. Using Drosophila , Karpac, Biteau, and Jasper show that the transcription factor Foxo regulates intestinal lipid homeostasis as part of an adaptive response to dietary changes and that chronic intestinal activation of Foxo with age leads to the disruption of lipid metabolism. These results demonstrate that changes in the regulation of adaptive signaling mechanisms can contribute to the age-associated breakdown of metabolic homeostasis.

Description: Publication date: Available online 13 September 2013 Source: Geoscience Frontiers Author(s): K. Naganjaneyulu

Description: Publication date: Available online 17 September 2013 Source: FEBS Open Bio Author(s): Rasheda Sultana , Maria A. Theodoraki , Avrom J. Caplan The UBR1 ubiquitin ligase promotes degradation of proteins via the N-end rule and by another mechanism that detects a misfolded conformation. Although UBR1 was shown recently to act on protein kinases whose misfolding was promoted by inhibition of Hsp90, it was unknown whether this ubiquitin ligase targeted other client types of the chaperone. We analyzed the role of UBR1 in the degradation of nuclear receptors that are classical clients of Hsp90. Our results showed that UBR1 deletion results in impaired degradation of the glucocorticoid receptor and the androgen receptor but not the estrogen receptor α. These findings demonstrate specificity in the actions of the UBR1 ubiquitin ligase in the degradation of Hsp90 clients in the presence of small molecule inhibitors that promote client misfolding. Graphical abstract

Description: Publication date: Available online 19 September 2013 Source: Cell Reports Author(s): George E. Gentsch , Nick D.L. Owens , Stephen R. Martin , Paul Piccinelli , Tiago Faial , Matthew W.B. Trotter , Michael J. Gilchrist , James C. Smith The design of effective cell replacement therapies requires detailed knowledge of how embryonic stem cells form primary tissues, such as mesoderm or neurectoderm that later become skeletal muscle or nervous system. Members of the T-box transcription factor family are key in the formation of these primary tissues, but their underlying molecular activities are poorly understood. Here, we define in vivo genome-wide regulatory inputs of the T-box proteins Brachyury, Eomesodermin, and VegT, which together maintain neuromesodermal stem cells and determine their bipotential fates in frog embryos. These T-box proteins are all recruited to the same genomic recognition sites, from where they activate genes involved in stem cell maintenance and mesoderm formation while repressing neurogenic genes. Consequently, their loss causes embryos to form an oversized neural tube with no mesodermal derivatives. This collaboration between T-box family members thus ensures the continuous formation of correctly proportioned neural and mesodermal tissues in vertebrate embryos during axial elongation. Graphical abstract Teaser The development of effective cell replacement therapies requires detailed knowledge of how embryonic stem cells form primary tissues, such as mesoderm or neurectoderm that later become skeletal muscle or spinal cord. Gentsch, Smith, and colleagues now provide mechanistic insight into how T-box transcription factors regulate stem cells to form neural or mesodermal tissues. The authors show how this ensures the harmonious formation of spinal cord, muscle, and notochord as the vertebrate embryo elongates along its anteroposterior axis.

Description: Publication date: Available online 19 September 2013 Source: Cell Reports Author(s): Ivan Zanoni , Roberto Spreafico , Caterina Bodio , Marco Di Gioia , Clara Cigni , Achille Broggi , Tatiana Gorletta , Michele Caccia , Giuseppe Chirico , Laura Sironi , Maddalena Collini , Mario P. Colombo , Natalio Garbi , Francesca Granucci Natural killer (NK) cells have antitumor, antiviral, and antibacterial functions, and efforts are being made to manipulate them in immunotherapeutic approaches. However, their activation mechanisms remain poorly defined, particularly during bacterial infections. Here, we show that upon lipopolysaccharide or E. coli exposure, dendritic cells (DCs) produce three cytokines—interleukin 2 (IL-2), IL-18, and interferon β (IFN-β)—necessary and sufficient for NK cell activation. IFN-β enhances NK cell activation by inducing IL-15 and IL-15 receptor α not only in DCs but, surprisingly, also in NK cells. This process allows the transfer of IL-15 on NK cell surface and its cis presentation. cis -presented NK cell-derived and trans -presented DC-derived IL-15 contribute equally to optimal NK cell activation. Graphical abstract Teaser NK cells depend on IL-15 provided by accessory cells for their survival under steady-state conditions. It has long been believed that a similar requirement is applied to NK cell activation as well. Zanoni, Granucci, and colleagues now show that NK cells express IL-15 and IL-15Rα when stimulated by type I interferons. NK cells cis -present self-produced IL-15, and this is as important to NK cell activation as trans presentation of IL-15 by dendritic cells.

Description: Publication date: Available online 19 September 2013 Source: Cell Reports Author(s): Oren Ben-Ami , Dan Friedman , Dena Leshkowitz , Dalia Goldenberg , Kira Orlovsky , Niv Pencovich , Joseph Lotem , Amos Tanay , Yoram Groner The t(8;21) and inv(16) chromosomal aberrations generate the oncoproteins AML1-ETO (A-E) and CBFβ-SMMHC (C-S). The role of these oncoproteins in acute myeloid leukemia (AML) etiology has been well studied. Conversely, the function of native RUNX1 in promoting A-E- and C-S-mediated leukemias has remained elusive. We show that wild-type RUNX1 is required for the survival of t(8;21)-Kasumi-1 and inv(16)-ME-1 leukemic cells. RUNX1 knockdown in Kasumi-1 cells (Kasumi-1 RX1-KD ) attenuates the cell-cycle mitotic checkpoint, leading to apoptosis, whereas knockdown of A-E in Kasumi-1 RX1-KD rescues these cells. Mechanistically, a delicate RUNX1/A-E balance involving competition for common genomic sites that regulate RUNX1/A-E targets sustains the malignant cell phenotype. The broad medical significance of this leukemic cell addiction to native RUNX1 is underscored by clinical data showing that an active RUNX1 allele is usually preserved in both t(8;21) or inv(16) AML patients, whereas RUNX1 is frequently inactivated in other forms of leukemia. Thus, RUNX1 and its mitotic control targets are potential candidates for new therapeutic approaches. Graphical abstract Teaser The t(8;21) and inv(16) chimeric oncogenes are major etiological drivers of human acute myeloid leukemia. However, the function of native RUNX1 in these leukemias has remained unknown. Groner and colleagues demonstrate that expression of wild-type RUNX1 is essential for t(8;21) and inv(16) leukemogenesis. Reducing RUNX1 activity destines the leukemic cells for apoptosis. Importantly, an active RUNX1 allele is usually preserved in t(8;21) or inv(16) patients, whereas, in other leukemias, it is frequently inactivated, underscoring the significance of this leukemic cell addiction to RUNX1.

Description: Publication date: Available online 19 September 2013 Source: Cell Reports Author(s): Markus Reschke , John G. Clohessy , Nina Seitzer , Daniel P. Goldstein , Susanne B. Breitkopf , Daniel B. Schmolze , Ugo Ala , John M. Asara , Andrew H. Beck , Pier Paolo Pandolfi Increasing evidence points to an important role for the ribosome in the regulation of biological processes and as a target for deregulation in disease. Here, we describe a SILAC (stable isotope labeling by amino acids in cell culture)-based mass spectrometry approach to probing mammalian riboproteomes. Using a panel of cell lines, as well as genetic and pharmacological perturbations, we obtained a comparative characterization of the cellular riboproteome. This analysis identified a set of riboproteome components, consisting of a diverse array of proteins with a strong enrichment for RNA-binding proteins. Importantly, this global analysis uncovers a high incidence of genetic alterations to riboproteome components in cancer, with a distinct bias toward genetic amplification. We further validated association with polyribosomes for several riboproteome components and demonstrate that enrichment at the riboproteome can depend on cell type, genetics, or cellular stimulus. Our results have important implications for the understanding of how ribosomes function and provide a platform for uncovering regulators of translation. Graphical abstract Teaser Increasing evidence points to an important role for the ribosome in regulating biological processes and as a target in disease. Now, Pandolfi and colleagues use mass spectrometry to probe the mammalian riboproteome. They show that the riboproteome displays differential composition in cancer cells and contains an array of proteins, many of which are frequently amplified in cancer. These results have important implications for the understanding of how ribosomes function and provide a platform to broaden our understanding of translational regulation.

Description: Publication date: Available online 19 September 2013 Source: Cell Reports Author(s): Shunqiang Li , Dong Shen , Jieya Shao , Robert Crowder , Wenbin Liu , Aleix Prat , Xiaping He , Shuying Liu , Jeremy Hoog , Charles Lu , Li Ding , Obi L. Griffith , Christopher Miller , Dave Larson , Robert S. Fulton , Michelle Harrison , Tom Mooney , Joshua F. McMichael , Jingqin Luo , Yu Tao , Rodrigo Goncalves , Christopher Schlosberg , Jeffrey F. Hiken , Laila Saied , Cesar Sanchez , Therese Giuntoli , Caroline Bumb , Crystal Cooper , Robert T. Kitchens , Austin Lin , Chanpheng Phommaly , Sherri R. Davies , Jin Zhang , Megha Shyam Kavuri , Donna McEachern , Yi Yu Dong , Cynthia Ma , Timothy Pluard , Michael Naughton , Ron Bose , Rama Suresh , Reida McDowell , Loren Michel , Rebecca Aft , William Gillanders , Katherine DeSchryver , Richard K. Wilson , Shaomeng Wang , Gordon B. Mills , Ana Gonzalez-Angulo , John R. Edwards , Christopher Maher , Charles M. Perou , Elaine R. Mardis , Matthew J. Ellis To characterize patient-derived xenografts (PDXs) for functional studies, we made whole-genome comparisons with originating breast cancers representative of the major intrinsic subtypes. Structural and copy number aberrations were found to be retained with high fidelity. However, at the single-nucleotide level, variable numbers of PDX-specific somatic events were documented, although they were only rarely functionally significant. Variant allele frequencies were often preserved in the PDXs, demonstrating that clonal representation can be transplantable. Estrogen-receptor-positive PDXs were associated with ESR1 ligand-binding-domain mutations, gene amplification, or an ESR1/YAP1 translocation. These events produced different endocrine-therapy-response phenotypes in human, cell line, and PDX endocrine-response studies. Hence, deeply sequenced PDX models are an important resource for the search for genome-forward treatment options and capture endocrine-drug-resistance etiologies that are not observed in standard cell lines. The originating tumor genome provides a benchmark for assessing genetic drift and clonal representation after transplantation. Graphical abstract Teaser In this study, Ellis and colleagues compare whole-tumor genomes from drug-resistant breast cancers with paired xenografts. Genomic fidelity upon transplantation was high for structural variants but variable at the single-nucleotide level. Therefore, tumor and xenograft whole-genome comparisons critically assess genetic drift and clonal representation. Additional analysis revealed ESR1 mutations, amplification, and translocations associated with endocrine resistance in lumenal xenografts. Sequenced patient-derived xenografts are an important resource for functional genomics and capture treatment-resistance etiologies that are not observed in standard cell lines.

Description: Publication date: Available online 26 September 2013 Source: Cell Reports Author(s): Jun Ding , Ursula Loizides-Mangold , Gianpaolo Rando , Vincent Zoete , Olivier Michielin , Janardan K. Reddy , Walter Wahli , Howard Riezman , Bernard Thorens Specific metabolic pathways are activated by different nutrients to adapt the organism to available resources. Although essential, these mechanisms are incompletely defined. Here, we report that medium-chain fatty acids contained in coconut oil, a major source of dietary fat, induce the liver ω-oxidation genes Cyp4a10 and Cyp4a14 to increase the production of dicarboxylic fatty acids. Furthermore, these activate all ω- and β-oxidation pathways through peroxisome proliferator activated receptor (PPAR) α and PPARγ, an activation loop normally kept under control by dicarboxylic fatty acid degradation by the peroxisomal enzyme L-PBE. Indeed, L-pbe −/− mice fed coconut oil overaccumulate dicarboxylic fatty acids, which activate all fatty acid oxidation pathways and lead to liver inflammation, fibrosis, and death. Thus, the correct homeostasis of dicarboxylic fatty acids is a means to regulate the efficient utilization of ingested medium-chain fatty acids, and its deregulation exemplifies the intricate relationship between impaired metabolism and inflammation. Graphical abstract Teaser Specific metabolic pathways are activated by different nutrients to adapt the organism to available resources. Riezman, Thorens, and colleagues find that mice lacking the peroxisomal L-bifunctional enzyme (L-pbe) die of liver failure when fed coconut oil but not lard. Medium-chain fatty acids in coconut oil induce the liver ω-oxidation to increase the production of dicarboxylic fatty acids (DCAs). Furthermore, these activate all ω- and β-oxidation pathways through peroxisome proliferator activated receptors, an activation loop normally fine tuned by L-PBE degrading DCAs. Their work demonstrates the physiological role of mouse L-PBE in hepatic adaptation to medium-chain fatty acids.

Description: Publication date: Available online 26 September 2013 Source: Cell Reports Author(s): Tae Kyung Kim , Jai-Yoon Sul , Henrik Helmfors , Ulo Langel , Junhyong Kim , James Eberwine Protein synthesis in neuronal dendrites underlies long-term memory formation in the brain. Local translation of reporter mRNAs has demonstrated translation in dendrites at focal points called translational hotspots. Various reports have shown that hundreds to thousands of mRNAs are localized to dendrites, yet the dynamics of translation of multiple dendritic mRNAs has remained elusive. Here, we show that the protein translational activities of two dendritically localized mRNAs are spatiotemporally complex but constrained by the translational hotspots in which they are colocalized. Cotransfection of glutamate receptor 2 (GluR2) and GluR4 mRNAs (engineered to encode different fluorescent proteins) into rat hippocampal neurons demonstrates a heterogeneous distribution of translational hotspots for the two mRNAs along dendrites. Stimulation with s -3,5-dihydroxy-phenylglycine modifies the translational dynamics of both of these RNAs in a complex saturable manner. These results suggest that the translational hotspot is a primary structural regulator of the simultaneous yet differential translation of multiple mRNAs in the neuronal dendrite. Graphical abstract Teaser Local translation of dendritic mRNAs plays a crucial role in synaptic plasticity and formation of long-term memory. However, the dynamics of simultaneous translation of multiple dendritic mRNAs has remained elusive. In this study, Eberwine and colleagues show that the translational activities of two dendritically localized mRNAs are spatiotemporally complex but constrained by the translational hotspots in which they are colocalized. The results suggest structural constraints and stochastic regulation of synaptic plasticity.

Description: Publication date: Available online 26 September 2013 Source: Cell Reports Author(s): Sara Ribeiro , Ilaria Napoli , Ian J. White , Simona Parrinello , Adrienne M. Flanagan , Ueli Suter , Luis F. Parada , Alison C. Lloyd Schwann cells are highly plastic cells that dedifferentiate to a progenitor-like state following injury. However, deregulation of this plasticity, may be involved in the formation of neurofibromas, mixed-cell tumors of Schwann cell (SC) origin that arise upon loss of NF1. Here, we show that adult myelinating SCs (mSCs) are refractory to Nf1 loss. However, in the context of injury, Nf1-deficient cells display opposing behaviors along the wounded nerve; distal to the injury, Nf1 −/− mSCs redifferentiate normally, whereas at the wound site Nf1 −/− mSCs give rise to neurofibromas in both Nf1 +/+ and Nf1 +/− backgrounds. Tracing experiments showed that distinct cell types within the tumor derive from Nf1-deficient SCs. This model of neurofibroma formation demonstrates that neurofibromas can originate from adult SCs and that the nerve environment can switch from tumor suppressive to tumor promoting at a site of injury. These findings have implications for both the characterization and treatment of neurofibromas. Graphical abstract Teaser Neurofibromas are mixed-cell tumors of Schwann cell (SC) origin that arise upon loss of NF1. Here, Lloyd and colleagues show that adult myelinating SCs (mSCs) are insensitive to NF1 loss. However, when nerves are injured, NF1-deficient mSCs display opposing behavior along the wounded nerve, forming tumors at the injury site while redifferentiating normally along the rest of the nerve. This demonstrates that the nerve environment can switch from tumor suppressive to tumor promoting at a site of injury.

Description: Publication date: Available online 26 September 2013 Source: Cell Reports Author(s): Hui Zheng , Vibhor Gupta , Jeffrey Patterson-Fortin , Sabyasachi Bhattacharya , Kanstantsin Katlinski , Junmin Wu , Bentley Varghese , Christopher J. Carbone , Bernadette Aressy , Serge Y. Fuchs , Roger A. Greenberg Lysine63-linked ubiquitin (K63-Ub) chains represent a particular ubiquitin topology that mediates proteasome-independent signaling events. The deubiquitinating enzyme (DUB) BRCC36 segregates into distinct nuclear and cytoplasmic complexes that are specific for K63-Ub hydrolysis. RAP80 targets the five-member nuclear BRCC36 complex to K63-Ub chains at DNA double-strand breaks. The alternative four-member BRCC36 containing complex (BRISC) lacks a known targeting moiety. Here, we identify serine hydroxymethyltransferase (SHMT) as a previously unappreciated component that fulfills this function. SHMT directs BRISC activity at K63-Ub chains conjugated to the type 1 interferon (IFN) receptor chain 1 (IFNAR1). BRISC-SHMT2 complexes localize to and deubiquitinate actively engaged IFNAR1, thus limiting its K63-Ub-mediated internalization and lysosomal degradation. BRISC-deficient cells and mice exhibit attenuated responses to IFN and are protected from IFN-associated immunopathology. These studies reveal a mechanism of DUB regulation and suggest a therapeutic use of BRISC inhibitors for treating pathophysiological processes driven by elevated IFN responses. Graphical abstract Teaser Fuchs, Greenberg, and colleagues describe a deubiquitinating (DUB) enzyme complex consisting of an interaction between BRISC and SHMT enzymes. This lysine63-ubiquitin-specific DUB complex deubiquitinates the actively engaged type I interferon receptor, resulting in receptor stabilization and activation of interferon signaling pathways. BRISC-deficient cells and mice have attenuated interferon responses and are resistant to bacterial lipopolysaccharide. These findings suggest strategies for treating disease states that arise from elevated interferon signals.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Tamás Schauer , Petra C. Schwalie , Ava Handley , Carla E. Margulies , Paul Flicek , Andreas G. Ladurner Chromatin organization and gene activity are responsive to developmental and environmental cues. Although many genes are transcribed throughout development and across cell types, much of gene regulation is highly cell-type specific. To readily track chromatin features at the resolution of cell types within complex tissues, we developed and validated chromatin affinity purification from specific cell types by chromatin immunoprecipitation (CAST-ChIP), a broadly applicable biochemical procedure. RNA polymerase II (Pol II) CAST-ChIP identifies ∼1,500 neuronal and glia-specific genes in differentiated cells within the adult Drosophila brain. In contrast, the histone H2A.Z is distributed similarly across cell types and throughout development, marking cell-type-invariant Pol II-bound regions. Our study identifies H2A.Z as an active chromatin signature that is refractory to changes across cell fates. Thus, CAST-ChIP powerfully identifies cell-type-specific as well as cell-type-invariant chromatin states, enabling the systematic dissection of chromatin structure and gene regulation within complex tissues such as the brain. Graphical abstract Teaser Much gene regulation is cell-type specific, but there are few tools that allow the genome-wide tracking of chromatin features and transcriptional states at the resolution of cell types within complex tissues. Margulies, Flicek, Ladurner, and colleagues developed and validated CAST-ChIP, a biochemical procedure that profiles chromatin-associated proteins in cell types of the Drosophila brain. CAST-ChIP identified 1,500 neuron- and glia-specific genes and revealed that histone H2A.Z marks cell-type-invariant domains. CAST-ChIP enables the systematic dissection of gene regulation in cell types.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Per Nilsson , Krishnapriya Loganathan , Misaki Sekiguchi , Yukio Matsuba , Kelvin Hui , Satoshi Tsubuki , Motomasa Tanaka , Nobuhisa Iwata , Takashi Saito , Takaomi C. Saido Alzheimer’s disease (AD) is a neurodegenerative disease biochemically characterized by aberrant protein aggregation, including amyloid beta (Aβ) peptide accumulation. Protein aggregates in the cell are cleared by autophagy, a mechanism impaired in AD. To investigate the role of autophagy in Aβ pathology in vivo, we crossed amyloid precursor protein (APP) transgenic mice with mice lacking autophagy in excitatory forebrain neurons obtained by conditional knockout of autophagy-related protein 7. Remarkably, autophagy deficiency drastically reduced extracellular Aβ plaque burden. This reduction of Aβ plaque load was due to inhibition of Aβ secretion, which led to aberrant intraneuronal Aβ accumulation in the perinuclear region. Moreover, autophagy-deficiency-induced neurodegeneration was exacerbated by amyloidosis, which together severely impaired memory. Our results establish a function for autophagy in Aβ metabolism: autophagy influences secretion of Aβ to the extracellular space and thereby directly affects Aβ plaque formation, a pathological hallmark of AD. Graphical abstract Teaser In this study, Nilsson, Saido, and colleagues show that autophagy influences secretion of Alzheimer’s disease (AD) amyloid beta (Aβ) peptide. Autophagy deficiency, achieved by genetic deletion of autophagy-related gene 7 in excitatory neurons in mouse brain, reduced Aβ plaque load and caused intracellular Aβ accumulation. In addition, amyloidosis exacerbated autophagy-deficiency-induced neurodegeneration and caused severe memory impairment. Thus, autophagy has a key role in the two main characteristics of AD: intracellular Aβ accumulation and extracellular Aβ plaque formation.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Antonia Borovina , Brian Ciruna The role for cilia in establishing planar cell polarity (PCP) is contentious. Although knockdown of genes known to function in ciliogenesis has been reported to cause PCP-related morphogenesis defects in zebrafish, genetic mutations affecting intraflagellar transport (IFT) do not show PCP phenotypes despite the requirement for IFT in cilia formation. This discrepancy has been attributed to off-target effects of antisense morpholino oligonucleotide (MO) injection, confounding maternal effects in zygotic mutant embryos, or an inability to distinguish between cilia-dependent versus cilia-independent protein functions. To determine the role of cilia in PCP, we generated maternal + zygotic IFT88 (MZ ift88 ) mutant zebrafish embryos, which never form cilia. We clearly demonstrate that cilia are not required to establish PCP. Rather, IFT88 plays a cilia-independent role in controlling oriented cell divisions at gastrulation and neurulation. Our results have important implications for the interpretation of cilia gene function in normal development and in disease. Graphical abstract Teaser The role of cilia in establishing planar cell polarity (PCP) remains contentious, confounded by off-target effects of antisense morpholino oligonucleotide use, maternal effects in zygotic mutant backgrounds, and difficulties distinguishing between cilia-dependent versus cilia-independent protein function. Here, Borovina and Ciruna clearly demonstrate that PCP is established normally in cilia-deficient maternal-zygotic IFT88 mutant zebrafish. Furthermore, by analyzing morphogenic events that occur prior to cilia formation, they identify a cilia- and PCP-independent role for IFT88 in controlling polarized cell divisions.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Tian Xie , Wei Peng , Chuangye Yan , Jianping Wu , Xinqi Gong , Yigong Shi RIP3 is an essential upstream kinase in necroptosis. The pseudokinase MLKL functions as a substrate of RIP3 to mediate downstream signaling. The molecular mechanism by which RIP3 recognizes and phosphorylates MLKL remains unknown. Here, we report the crystal structures of the mouse RIP3 kinase domain, the MLKL kinase-like domain, and a binary complex between the two. Both RIP3 and MLKL adopt the canonical kinase fold. Free RIP3 exists in an active conformation, whereas MLKL-bound RIP3 is stabilized by AMP-PNP to adopt an inactive conformation. The formation of the RIP3-MLKL complex, involving their respective N- and C-lobes, is accompanied by pronounced conformational changes of the αC helix and activation loop in RIP3 and the corresponding structural elements in MLKL. RIP3-mediated MLKL phosphorylation, though important for downstream signaling, is dispensable for stable complex formation between RIP3 and MLKL. Our study serves as a framework for mechanistic understanding of RIP3-mediated necroptotic signaling. Graphical abstract Teaser RIP3 is an essential upstream kinase in necroptosis. The pseudokinase MLKL functions as a substrate of RIP3 to mediate downstream signaling. In this study, Shi and colleagues report the crystal structures of the mouse RIP3 kinase domain, the MLKL kinase-like domain, and a binary complex between the two, which reveals the structural basis of MLKL recognition by RIP3 and gives structural insights into RIP3-mediated necroptotic signaling. Their structural analysis serves as a framework for understanding RIP3-mediated necroptosis.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Albert Ribes-Zamora , Sandra M. Indiviglio , Ivana Mihalek , Christopher L. Williams , Alison A. Bertuch Telomeres are protected from nonhomologous end-joining (NHEJ) to avoid deleterious chromosome fusions, yet they associate with the Ku heterodimer that is principal in the classical NHEJ (c-NHEJ) pathway. T-loops have been proposed to inhibit Ku’s association with telomeric ends, thus inhibiting c-NHEJ; however, deficiencies in the t-loop model suggest additional mechanisms are in effect. We demonstrate that TRF2 interacts with Ku at telomeres and via residues in Ku70 helix 5 (α5), which are vital for NHEJ. We show that Ku’s interaction with a TRF2 mutant that induces telomeric fusions is significantly impaired. Additionally, we demonstrate that Ku70 α5 is required for Ku self-association in live cells, which can bridge DNA ends. Together, these findings lead us to propose a model in which telomeres are directly protected from c-NHEJ via TRF2 impeding Ku’s ability to synapse telomere ends. Graphical abstract Teaser The protection of chromosomal termini from fusions is an essential function of telomeres. Nonetheless, the Ku heterodimer, a factor required for nonhomologous end-joining (NHEJ), is associated with functional telomeres. In this study, Bertuch and colleagues show that the telomere end protection factor TRF2 interacts with a region of Ku required for NHEJ. They further show that this region promotes Ku-Ku interactions. These data lead the authors to propose a model for the protection of telomeres from NHEJ.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Hong Wu , Nikolas Mathioudakis , Boubou Diagouraga , Aiping Dong , Ludmila Dombrovski , Frédéric Baudat , Stephen Cusack , Bernard de Massy , Jan Kadlec PRDM9, a histone lysine methyltransferase, is a key determinant of the localization of meiotic recombination hot spots in humans and mice and the only vertebrate protein known to be involved in hybrid sterility. Here, we report the crystal structure of the PRDM9 methyltransferase domain in complex with a histone H3 peptide dimethylated on lysine 4 (H3K4me2) and S-adenosylhomocysteine (AdoHcy), which provides insights into the methyltransferase activity of PRDM proteins. We show that the genuine substrate of PRDM9 is histone H3 lysine 4 (H3K4) and that the enzyme possesses mono-, di-, and trimethylation activities. We also determined the crystal structure of PRDM9 in its autoinhibited state, which revealed a rearrangement of the substrate and cofactor binding sites by a concerted action of the pre-SET and post-SET domains, providing important insights into the regulatory mechanisms of histone lysine methyltransferase activity. Graphical abstract Teaser The histone methyltransferase PRDM9 is a key determinant of meiotic recombination hot spots in humans and mice and the only vertebrate protein known to be involved in hybrid sterility. In this study, de Massy, Kadlec, and colleagues analyzed PRDM9 substrate specificity and report the crystal structures of its methyltransferase domain in an autoinhibited state and in complex with an H3K4me2 peptide and AdoHcy. These data provide important insights into the regulatory mechanisms of histone lysine methyltransferase activity.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Gwynneth Thomas , Jenna L. Betters , Caleb C. Lord , Amanda L. Brown , Stephanie Marshall , Daniel Ferguson , Janet Sawyer , Matthew A. Davis , John T. Melchior , Lawrence C. Blume , Allyn C. Howlett , Pavlina T. Ivanova , Stephen B. Milne , David S. Myers , Irina Mrak , Vera Leber , Christoph Heier , Ulrike Taschler , Jacqueline L. Blankman , Benjamin F. Cravatt , Richard G. Lee , Rosanne M. Crooke , Mark J. Graham , Robert Zimmermann , H. Alex Brown , J. Mark Brown The serine hydrolase α/β hydrolase domain 6 (ABHD6) has recently been implicated as a key lipase for the endocannabinoid 2-arachidonylglycerol (2-AG) in the brain. However, the biochemical and physiological function for ABHD6 outside of the central nervous system has not been established. To address this, we utilized targeted antisense oligonucleotides (ASOs) to selectively knock down ABHD6 in peripheral tissues in order to identify in vivo substrates and understand ABHD6’s role in energy metabolism. Here, we show that selective knockdown of ABHD6 in metabolic tissues protects mice from high-fat-diet-induced obesity, hepatic steatosis, and systemic insulin resistance. Using combined in vivo lipidomic identification and in vitro enzymology approaches, we show that ABHD6 can hydrolyze several lipid substrates, positioning ABHD6 at the interface of glycerophospholipid metabolism and lipid signal transduction. Collectively, these data suggest that ABHD6 inhibitors may serve as therapeutics for obesity, nonalcoholic fatty liver disease, and type II diabetes. Graphical abstract Teaser Metabolic syndrome has become a leading health concern. Now, Brown and colleagues show that that serine hydrolase ABHD6 is a key driver of the metabolic syndrome and that inhibition of ABHD6 protects mice from high-fat-diet-induced obesity, hepatic steatosis, and systemic insulin resistance. Using combined in vivo lipidomic and in vitro enzymology approaches, the authors show that ABHD6 is a promiscuous lipase that hydrolyzes monoacylglycerols and lysophospholipids and argue that ABHD6 inhibitors may hold therapeutic promise.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Kinyui Alice Lo , Adam Labadorf , Norman J. Kennedy , Myoung Sook Han , Yoon Sing Yap , Bryan Matthews , Xiaofeng Xin , Lei Sun , Roger J. Davis , Harvey F. Lodish , Ernest Fraenkel Diet-induced obesity (DIO) predisposes individuals to insulin resistance, and adipose tissue has a major role in the disease. Insulin resistance can be induced in cultured adipocytes by a variety of treatments, but what aspects of the in vivo responses are captured by these models remains unknown. We use global RNA sequencing to investigate changes induced by TNF-α, hypoxia, dexamethasone, high insulin, and a combination of TNF-α and hypoxia, comparing the results to the changes in white adipose tissue from DIO mice. We found that different in vitro models capture distinct features of DIO adipose insulin resistance, and a combined treatment of TNF-α and hypoxia is most able to mimic the in vivo changes. Using genome-wide DNase I hypersensitivity followed by sequencing, we further examined the transcriptional regulation of TNF-α-induced insulin resistance, and we found that C/EPBβ is a potential key regulator of adipose insulin resistance. Graphical abstract Teaser Obesity-related insulin resistance is an increasingly common medical problem. Lodish, Fraenkel, and colleagues examine in vitro models for adipose insulin resistance using next-generation sequencing to analyze mRNA levels and chromatin states. They demonstrate that common models capture dramatically different aspects of the in vivo changes, with a combined TNF-α-hypoxia treatment most able to mimic diet-induced obesity. Their approach reveals C/EPBβ as a potential regulator of adipose insulin resistance. AdipoSight, a web portal, provides access to their data and algorithms.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Ricardo Weinlich , Andrew Oberst , Christopher P. Dillon , Laura J. Janke , Sandra Milasta , John R. Lukens , Diego A. Rodriguez , Prajwal Gurung , Chandra Savage , Thirumala D. Kanneganti , Douglas R. Green Caspase-8 or cellular FLICE-like inhibitor protein (cFLIP) deficiency leads to embryonic lethality in mice due to defects in endothelial tissues. Caspase-8 −/− and receptor-interacting protein kinase-3 (RIPK3) −/− , but not cFLIP −/− and RIPK3 −/− , double-knockout animals develop normally, indicating that caspase-8 antagonizes the lethal effects of RIPK3 during development. Here, we show that the acute deletion of caspase-8 in the gut of adult mice induces enterocyte death, disruption of tissue homeostasis, and inflammation, resulting in sepsis and mortality. Likewise, acute deletion of caspase-8 in a focal region of the skin induces local keratinocyte death, tissue disruption, and inflammation. Strikingly, RIPK3 ablation rescues both phenotypes. However, acute loss of cFLIP in the skin produces a similar phenotype that is not rescued by RIPK3 ablation. TNF neutralization protects from either acute loss of caspase-8 or cFLIP. These results demonstrate that caspase-8-mediated suppression of RIPK3-induced death is required not only during development but also for adult homeostasis. Furthermore, RIPK3-dependent inflammation is dispensable for the skin phenotype. Graphical abstract Teaser In this study, Green and colleagues show that acute loss of caspase-8 in the gut or the skin can induce a TNF-dependent, RIPK3-mediated loss of tissue homeostasis and inflammation, demonstrating that RIPK3 function is tightly regulated in adult tissues. Strikingly, the authors show that loss of cFLIP in RIPK3-deficient background induces a similar phenotype, suggesting that loss of tissue barrier function, rather than the type of cell death (necroptosis or apoptosis), defines the onset of disease.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Todd C. Metzger , Imran S. Khan , James M. Gardner , Maria L. Mouchess , Kellsey P. Johannes , Anna K. Krawisz , Katarzyna M. Skrzypczynska , Mark S. Anderson Thymic epithelial cells in the medulla (mTECs) play a critical role in enforcing central tolerance through expression and presentation of tissue-specific antigens (TSAs) and deletion of autoreactive thymocytes. TSA expression requires autoimmune regulator (Aire), a transcriptional activator present in a subset of mTECs characterized by high CD80 and major histocompatibility complex II expression and a lack of potential for differentiation or proliferation. Here, using an Aire-DTR transgenic line, we show that short-term ablation specifically targets Aire + mTECs, which quickly undergo RANK-dependent recovery. Repeated ablation also affects Aire − mTECs, and using an inducible Aire-Cre fate-mapping system, we find that this results from the loss of a subset of mTECs that showed prior expression of Aire, maintains intermediate TSA expression, and preferentially migrates toward the center of the medulla. These results clearly identify a distinct stage of mTEC development and underscore the diversity of mTECs that play a key role in maintaining tolerance. Graphical abstract Teaser In this study, Anderson and colleagues investigate the recovery and developmental potential of Aire + thymic epithelial cells (TECs), a cell population with unique roles in limiting self-reactivity of developing T cells. The authors find that this population is capable of rapid recovery following targeted ablation and that such ablation leads to loss of tolerance to self. The authors also find that Aire + TECs progress to a terminal Aire − stage, which may have a unique role in driving central tolerance.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Anastazja Grabarz , Josée Guirouilh-Barbat , Aurélia Barascu , Gaëlle Pennarun , Diane Genet , Emilie Rass , Susanne M. Germann , Pascale Bertrand , Ian D. Hickson , Bernard S. Lopez The choice of the appropriate double-strand break (DSB) repair pathway is essential for the maintenance of genomic stability. Here, we show that the Bloom syndrome gene product, BLM, counteracts CtIP/MRE11-dependent long-range deletions (>200 bp) generated by alternative end-joining (A-EJ). BLM represses A-EJ in an epistatic manner with 53BP1 and RIF1 and is required for ionizing-radiation-induced 53BP1 focus assembly. Conversely, in the absence of 53BP1 or RIF1, BLM promotes formation of A-EJ long deletions, consistent with a role for BLM in DSB end resection. These data highlight a dual role for BLM that influences the DSB repair pathway choi (1) protection against CtIP/MRE11 long-range deletions associated with A-EJ and (2) promotion of DNA resection. These antagonist roles can be regulated, according to cell-cycle stage, by interacting partners such as 53BP1 and TopIII, to avoid unscheduled resection that might jeopardize genome integrity. Graphical abstract Teaser The choice of the appropriate double-strand break (DSB) repair pathway is essential for the maintenance of genomic stability. Here, Lopez and colleagues show a dual role for the Bloom syndrome gene product, BLM, that influences the DSB repair pathway choice in two ways: (1) protection against long-range deletions associated with DSB end-joining and (2) promotion of DNA resection. These antagonistic roles can be regulated, according to cell-cycle stage, by interacting partners, to avoid unscheduled resection that might jeopardize genome integrity.

Description: Publication date: Available online 3 October 2013 Source: Cell Reports Author(s): Samantha B. Foley , Zacariah L. Hildenbrand , Abigail A. Soyombo , Jeffery A. Magee , Yipin Wu , Katherine I. Oravecz-Wilson , Theodora S. Ross Chronic myeloid leukemia (CML) and some acute lymphoblastic leukemias are characterized by the t(9;22) chromosome, which encodes the BCR/ABL oncogene. Multiple mouse models of CML express BCR/ABL at high levels from non- Bcr promoters, resulting in the development of leukemias. In contrast, a significant fraction of healthy humans have been found to have BCR/ABL-positive hematopoietic cells. To bridge the gap between the information derived from current mouse models and nonleukemic humans with the BCR/ABL oncogene, we generated a knockin model with BCR/ABL p210 expressed from the Bcr locus. Unlike previous models, expression of BCR/ABL from the knockin allele did not induce leukemia. BCR/ABL mutant cells did exhibit favorable bone marrow engraftment compared to control cells. These data suggest that BCR/ABL expression alone is insufficient to induce disease. This model allows for inducible spatial and temporal control of BCR/ABL expression for analysis of early steps in the pathogenesis of BCR/ABL-expressing leukemias. Graphical abstract Teaser In this study, Ross and colleagues show that when the BCR/ABL oncogene is placed in the mouse genome as a single-copy knockin mutation, the mice, like some humans with the BCR/ABL mutation, are leukemia free. The combination of this BCR/ABL allele with an AML1/ETO knockin allele led to myeloid neoplasia. This mouse mutation will aid in understanding BCR/ABL-associated predisease, which many predict is the precursor to florid chronic myeloid leukemia.

Description: Bassem El Zoghbi, Rafael Estevez, and Christian Olagnon Intergranular slow crack growth in zirconia polycrystal is described with a cohesive zone model that simulate mechanically the reaction-rupture mechanism underlying stress and environmentally assisted failure. A 2D polycrystal is considered with cohesive surfaces inserted along the grain boundarie ... [Theor. Appl. Mech. Lett. 3 , 051001 (2013)] published Tue Sep 10, 2013 .

Description: Long Li, Jizeng Wang, and Youhe Zhou This study intends to investigate how the elasticity of a bacterial phage can affect the process of DNA packaging and ejection. For this purpose, we propose a unified continuum and statistical mechanics model by taking into account the effects of DNA bending deformation, electrostatic repulsion be ... [Theor. Appl. Mech. Lett. 3 , 054003 (2013)] published Tue Sep 10, 2013 .

Description: Ahmad Sedaghat and Mohammad Ali Badri In this study, a flow solver was developed based on the governing RANS equations of compressible flows and was further extended to include the effects of electromagnetic forces namely Lorentz forces. Lorentz forces may be added as a source term in the governing fluid flow equations. Numerical stud ... [Theor. Appl. Mech. Lett. 3 , 052003 (2013)] published Tue Sep 10, 2013 .

Description: Meie Li, Chao Jin, and Jinxiong Zhou Hydrogel can swell to many times of its dry volume, resulting in large deformation which is vital for its function. The swelling process is regulated by many physical and chemical mechanisms, and can, to some extent, be fairly described by the poroelasticity theory. Implementation of the poroelast ... [Theor. Appl. Mech. Lett. 3 , 054009 (2013)] published Tue Sep 10, 2013 .

Description: Chaofeng Lü, Wen Chen, and Jinxiong Zhou et al. Abstract not available. [Theor. Appl. Mech. Lett. 3 , 054001 (2013)] published Sun Sep 01, 2013 .

Description: Wenxiang Xu, Huisu Chen, and Wen Chen When interfacial layers are viewed as a separate phase, the interface thickness plays an essential role in assessing physico-mechanical properties of particulate materials. However, the interface thickness from sectional analysis is often overestimated, due to the irregularity of surface textures ... [Theor. Appl. Mech. Lett. 3 , 054008 (2013)] published Tue Sep 10, 2013 .

Description: Yu Wan, Quanshui Zheng, and Zhiping Xu Nano-particle capture is a key process in filtration, separation, and biomedical applications. Here we explored the mechanisms of soft particle capture using nanofiber networks. We identified possible states of the capture process, which are defined by their structural and material parameters. By ... [Theor. Appl. Mech. Lett. 3 , 054002 (2013)] published Tue Sep 10, 2013 .

Description: Ke-Qing Xia The system of turbulent thermal convection is introduced. Progresses in recent decades in the four major areas of research in turbulent convection are briefly reviewed. Some of the recent trends of the field are then discussed, which also serve to point out that the future directions in this impor ... [Theor. Appl. Mech. Lett. 3 , 052001 (2013)] published Tue Sep 10, 2013 .

Description: Publication date: Available online 12 September 2013 Source: Cell Reports Author(s): Ke Zhao , Juan Du , Xue Han , John L. Goodier , Peng Li , Xiaohong Zhou , Wei Wei , Sean L. Evans , Linzhang Li , Wenyan Zhang , Ling E. Cheung , Guanjun Wang , Haig H. Kazazian Jr. , Xiao-Fang Yu Long interspersed elements 1 (LINE-1) occupy at least 17% of the human genome and are its only active autonomous retrotransposons. However, the host factors that regulate LINE-1 retrotransposition are not fully understood. Here, we demonstrate that the Aicardi-Goutières syndrome gene product SAMHD1, recently revealed to be an inhibitor of HIV/simian immunodeficiency virus (SIV) infectivity and neutralized by the viral Vpx protein, is also a potent regulator of LINE-1 and LINE-1-mediated Alu/SVA retrotransposition. We also found that mutant SAMHD1s of Aicardi-Goutières syndrome patients are defective in LINE-1 inhibition. Several domains of SAMHD1 are critical for LINE-1 regulation. SAMHD1 inhibits LINE-1 retrotransposition in dividing cells. An enzymatic active site mutant SAMHD1 maintained substantial anti-LINE-1 activity. SAMHD1 inhibits ORF2p-mediated LINE-1 reverse transcription in isolated LINE-1 ribonucleoproteins by reducing ORF2p level. Thus, SAMHD1 may be a cellular regulator of LINE-1 activity that is conserved in mammals. Graphical abstract Teaser Long interspersed elements 1 (LINE-1) are active autonomous retrotransposons that occupy 17% of the human genome. The host factors that regulate LINE-1 retrotransposition are not fully understood. In this study, Yu and colleagues show that the Aicardi-Goutières syndrome (AGS) gene product, SAMHD1, is a potent regulator of LINE-1 retrotransposition. SAMHD1 mutants linked to AGS are defective in LINE-1 inhibition. Although SAMHD1 has also recently been shown to suppress HIV-1, the authors find that suppression of LINE-1 occurs through a distinct mechanism.

Description: Publication date: Available online 12 September 2013 Source: Cell Reports Author(s): Runsheng He , Ning Huang , Yitian Bao , Haining Zhou , Junlin Teng , Jianguo Chen During interphase, centrosomes are connected by a proteinaceous linker between the proximal ends of the centrioles, which is important for the centrosomes to function as a single microtubule-organizing center. However, the composition and regulation of centrosomal linker remain largely unknown. Here, we show that LRRC45 is a centrosome linker that localizes at the proximal ends of the centrioles and forms fiber-like structures between them. Depletion of LRRC45 results in centrosome splitting during interphase. Moreover, LRRC45 interacts with both C-Nap1 and rootletin and is phosphorylated by Nek2A at S661 during mitosis. After phosphorylation, both LRRC45 centrosomal localization and fiber-like structures are significantly reduced, which subsequently leads to centrosome separation. Thus, LRRC45 is a critical component of the proteinaceous linker between two centrioles and is required for centrosome cohesion. Graphical abstract Teaser During interphase, the centrosomes are connected by a loose proteinaceous linker. Here, Teng, Chen, and colleagues identify LRRC45 as a centrosome linker required for centrosome cohesion. It is recruited by C-Nap1 at the proximal ends of the centrioles and forms fiber-like structures, together with rootletin. Also, LRRC45 is phosphorylated by Nek2A, which induces centrosome separation during mitosis. These findings facilitate a better understanding of the composition and regulation of centrosome linkers.

Description: Publication date: Available online 12 September 2013 Source: Cell Reports Author(s): Ying Tan , Dinghui Yu , Germain U. Busto , Curtis Wilson , Ronald L. Davis Wnt signaling regulates synaptic plasticity and neurogenesis in the adult nervous system, suggesting a potential role in behavioral processes. Here, we probed the requirement for Wnt signaling during olfactory memory formation in Drosophila using an inducible RNAi approach. Interfering with β-catenin expression in adult mushroom body neurons specifically impaired long-term memory (LTM) without altering short-term memory. The impairment was reversible, being rescued by expression of a wild-type β-catenin transgene, and correlated with disruption of a cellular LTM trace. Inhibition of wingless , a Wnt ligand, and arrow , a Wnt coreceptor, also impaired LTM. Wingless expression in wild-type flies was transiently elevated in the brain after LTM conditioning. Thus, inhibiting three key components of the Wnt signaling pathway in adult mushroom bodies impairs LTM, indicating that this pathway mechanistically underlies this specific form of memory. Graphical abstract Teaser Wnt signaling is crucial for many aspects of embryonic development, including cell proliferation, cell movement, and cell-fate decisions. In this report, Davis and colleagues show that Wnt signaling is required for the formation of protein-synthesis-dependent, long-term memory. Using RNAi approaches that target Wnt signaling components in the adult fly mushroom body, they show that knockdown of the Wnt ligand wingless , the Wnt coreceptor arrow , and the effector molecule β-catenin all impair the formation of long-term behavioral memory as well as a cellular memory trace representing this form of memory.

Description: Publication date: Available online 19 September 2013 Source: FEBS Open Bio Author(s): Wei Chi , Xiaoni Gan , Wuhan Xiao , Wen Wang , Shunping He Hypoxia-inducible factor (HIF) is a crucial regulator of cellular and systemic responses to low oxygen levels. Here we firstly cloned three HIF-α isoforms from the basal branches of Osteichthyes and used computational tools to characterize the molecular change underlying the functional divergence of HIF-α isoforms in different lineages. Only the HIF-1α and HIF-2α in African lungfish and amphibians were found under positive selection. HIF-1α and -2α were less functionally divergent in basal ray-finned fish than in teleosts, and showed conserved but different transcriptional activity toward specific target genes.

Description: Publication date: Available online 19 September 2013 Source: Cell Reports Author(s): Hongxia Zhao , Alphée Michelot , Essi V. Koskela , Vadym Tkach , Dimitrios Stamou , David G. Drubin , Pekka Lappalainen Bin-Amphiphysin-Rvs (BAR) domain proteins are central regulators of many cellular processes involving membrane dynamics. BAR domains sculpt phosphoinositide-rich membranes to generate membrane protrusions or invaginations. Here, we report that, in addition to regulating membrane geometry, BAR domains can generate extremely stable lipid microdomains by “freezing” phosphoinositide dynamics. This is a general feature of BAR domains, because the yeast endocytic BAR and Fes/CIP4 homology BAR (F-BAR) domains, the inverse BAR domain of Pinkbar, and the eisosomal BAR protein Lsp1 induced phosphoinositide clustering and halted lipid diffusion, despite differences in mechanisms of membrane interactions. Lsp1 displays comparable low diffusion rates in vitro and in vivo, suggesting that BAR domain proteins also generate stable phosphoinositide microdomains in cells. These results uncover a conserved role for BAR superfamily proteins in regulating lipid dynamics within membranes. Stable microdomains induced by BAR domain scaffolds and specific lipids can generate phase boundaries and diffusion barriers, which may have profound impacts on diverse cellular processes. Graphical abstract Teaser Bin-Amphiphysin-Rvs (BAR) domain superfamily proteins are central membrane-sculpting proteins in all eukaryote cells. Here, Lappalainen and colleagues demonstrate that BAR domain scaffolds not only bend membranes but also affect lipid distribution and dynamics by dramatically inhibiting the lateral diffusion of phosphoinositides. The extremely stable BAR domain-induced phosphoinositide microdomains can generate lipid phase boundaries and diffusion barriers, which are likely to have profound impacts on a wide variety of cellular processes, including endocytosis.

Description: Publication date: Available online 25 September 2013 Source: FEBS Open Bio Author(s): Michal Slutzki , Maroor K. Jobby , Seth Chitayat , Alon Karpol , Bareket Dassa , Yoav Barak , Raphael Lamed , Steven P. Smith , Edward A. Bayer The cellulosome is a large extracellular multi-enzyme complex that facilitates the efficient hydrolysis and degradation of crystalline cellulosic substrates. During the course of our studies on the cellulosome of the rumen bacterium Ruminococcus flavefaciens, we focused on the critical ScaA dockerin (ScaADoc), the unique dockerin that incorporates the primary enzyme-integrating ScaA scaffoldin into the cohesin-bearing ScaB adaptor scaffoldin. In the absence of a high-resolution structure of the ScaADoc module, we generated a computational model, and, upon its analysis, we were surprised to discover a putative stacking interaction between an N-terminal Trp and a C-terminal Pro, which we termed intramolecular clasp. In order to verify the existence of such an interaction, these residues were mutated to alanine. Circular dichroism spectroscopy, intrinsic tryptophan and ANS fluorescence, and NMR spectroscopy indicated that mutation of these residues has a destabilizing effect on the functional integrity of the Ca 2+ -bound form of ScaADoc. Analysis of recently determined dockerin structures from other species revealed the presence of other well-defined intramolecular clasps, which consist of different types of interactions between selected residues at the dockerin termini. We propose that this thematic interaction may represent a major distinctive structural feature of the dockerin module. Graphical abstract

Description: Publication date: 26 September 2013 Source: Cell Reports, Volume 4, Issue 6 Author(s): Steffi Oesterreich , Adam M. Brufsky , Nancy E. Davidson In this issue of Cell Reports , Li et al. show that the analysis of genetic changes in patient-derived xenografts can reveal crucial details of tumor evolution, such as the emergence of functional estrogen receptor mutations in endocrine-resistant breast cancer.

Description: Publication date: Available online 26 September 2013 Source: Cell Reports Author(s): Lingjie Li , Bo Liu , Orly L. Wapinski , Miao-Chih Tsai , Kun Qu , Jiajing Zhang , Jeff C. Carlson , Meihong Lin , Fengqin Fang , Rajnish A. Gupta , Jill A. Helms , Howard Y. Chang Long noncoding RNAs (lncRNAs) are thought to be prevalent regulators of gene expression, but the consequences of lncRNA inactivation in vivo are mostly unknown. Here, we show that targeted deletion of mouse Hotair lncRNA leads to derepression of hundreds of genes, resulting in homeotic transformation of the spine and malformation of metacarpal-carpal bones. RNA sequencing and conditional inactivation reveal an ongoing requirement of Hotair to repress HoxD genes and several imprinted loci such as Dlk1-Meg3 and Igf2-H19 without affecting imprinting choice. Hotair binds to both Polycomb repressive complex 2, which methylates histone H3 at lysine 27 (H3K27), and Lsd1 complex, which demethylates histone H3 at lysine 4 (H3K4) in vivo. Hotair inactivation causes H3K4me3 gain and, to a lesser extent, H3K27me3 loss at target genes. These results reveal the function and mechanisms of Hotair lncRNA in enforcing a silent chromatin state at Hox and additional genes. Graphical abstract Teaser A targeted and conditional knockout of the lncRNA, Hotair , is now presented by Chang and colleagues. The authors find that Hotair disruption causes homeotic transformation and skeletal malformation during mouse development. Hotair knockout leads to derepression of multiple genes, including HoxD and several imprinted genes. Furthermore, Hotair interacts with PRC2 and LSD1, and Hotair deletion altered chromatin states at specific targets.

Description: Publication date: Available online 26 September 2013 Source: Cell Reports Author(s): Saskia Delpretti , Thomas Montavon , Marion Leleu , Elisabeth Joye , Athanasia Tzika , Michel Milinkovitch , Denis Duboule Hox genes are required for the development of the intestinal cecum, a major organ of plant-eating species. We have analyzed the transcriptional regulation of Hoxd genes in cecal buds and show that they are controlled by a series of enhancers located in a gene desert flanking the HoxD cluster. The start site of two opposite long noncoding RNAs (lncRNAs), Hotdog and Twin of Hotdog , selectively contacts the expressed Hoxd genes in the framework of a topological domain, coinciding with robust transcription of these genes during cecum budding. Both lncRNAs are specifically transcribed in the cecum, albeit bearing no detectable function in trans . Hedgehogs have kept this regulatory potential despite the absence of the cecum, suggesting that these mechanisms are used in other developmental situations. In this context, we discuss the implementation of a common “budding toolkit” between the cecum and the limbs. Graphical abstract Teaser The intestinal cecum is a major organ for plant-eating species. Duboule and colleagues report that a series of enhancers, along with the Hotdog lncRNA, selectively contact a subset of HoxD genes and form a 3D regulatory structure, which coincides with a topological domain and elicits robust transcription. Hedgehogs have kept this regulatory potential despite absence of the cecum, suggesting that these mechanisms are part of a common “budding toolkit” also used during limb bud development.

Description: Publication date: Available online 26 September 2013 Source: Cell Reports Author(s): Inna Shcherbakova , Aaron A. Hoskins , Larry J. Friedman , Victor Serebrov , Ivan R. Corrêa Jr. , Ming-Qun Xu , Jeff Gelles , Melissa J. Moore Removal of introns from nascent transcripts (pre-mRNAs) by the spliceosome is an essential step in eukaryotic gene expression. Previous studies have suggested that the earliest steps in spliceosome assembly in yeast are highly ordered and the stable recruitment of U1 small nuclear ribonucleoprotein particle (snRNP) to the 5′ splice site necessarily precedes recruitment of U2 snRNP to the branch site to form the “prespliceosome.” Here, using colocalization single-molecule spectroscopy to follow initial spliceosome assembly on eight different S. cerevisiae pre-mRNAs, we demonstrate that active yeast spliceosomes can form by both U1-first and U2-first pathways. Both assembly pathways yield prespliceosomes functionally equivalent for subsequent U5⋅U4/U6 tri-snRNP recruitment and for intron excision. Although fractional flux through the two pathways varies on different introns, both are operational on all introns studied. Thus, multiple pathways exist for assembling functional spliceosomes. These observations provide insight into the mechanisms of cross-intron coordination of initial spliceosome assembly. Graphical abstract Teaser Intron excision by the spliceosome is an essential process in eukaryotic gene expression. Gelles, Moore, and colleagues use single-molecule colocalization to monitor early spliceosome assembly events in yeast whole-cell extract. They demonstrate that pre-mRNAs can initiate the formation of functional spliceosomes by first binding either U1 or U2 snRNP. This branched pathway has important implications for mechanisms of cross-intron coordination during early spliceosome assembly.

Description: Publication date: Available online 26 September 2013 Source: Cell Reports Author(s): Naif Zaman , Lei Li , Maria Luz Jaramillo , Zhanpeng Sun , Chabane Tibiche , Myriam Banville , Catherine Collins , Mark Trifiro , Miltiadis Paliouras , Andre Nantel , Maureen O’Connor-McCourt , Edwin Wang Individual cancer cells carry a bewildering number of distinct genomic alterations (e.g., copy number variations and mutations), making it a challenge to uncover genomic-driven mechanisms governing tumorigenesis. Here, we performed exome sequencing on several breast cancer cell lines that represent two subtypes, luminal and basal. We integrated these sequencing data and functional RNAi screening data (for the identification of genes that are essential for cell proliferation and survival) onto a human signaling network. Two subtype-specific networks that potentially represent core-signaling mechanisms underlying tumorigenesis were identified. Within both networks, we found that genes were differentially affected in different cell lines; i.e., in some cell lines a gene was identified through RNAi screening, whereas in others it was genomically altered. Interestingly, we found that highly connected network genes could be used to correctly classify breast tumors into subtypes on the basis of genomic alterations. Further, the networks effectively predicted subtype-specific drug targets, which were experimentally validated. Graphical abstract Teaser In this study, Wang and colleagues examine cancer genome sequencing data in a framework of a signaling network integrated with genome-wide RNAi knockdown information. They show that cancer cell survival network genes recurrently switch roles, between essential and cancer driving, among cancer subtypes. Mutations and copy number variations driving tumorigenesis are selected to be convergent onto cell survival networks. Genomic alterations of cancer cell survival subtype-specific network genes successfully predicted cancer subtype-specific drug targets and accurately classified cancer subtypes.

Description: Publication date: Available online 27 September 2013 Source: Cell Reports Author(s): Elizabeth Garner , Yonghwan Kim , Francis P. Lach , Molly C. Kottemann , Agata Smogorzewska Holliday junctions (HJs), the DNA intermediates of homologous recombination, need to be faithfully processed in order to preserve genome integrity. In human cells, the BLM helicase complex promotes nonnucleolytic dissolution of double HJs. In vitro, HJs may be nucleolytically processed by MUS81-EME1, GEN1, and SLX4-SLX1. Here, we exploit human SLX4 -null cells to examine the requirements for HJ resolution in vivo. Lack of BLM and SLX4 or GEN1 and SLX4 is synthetically lethal in the absence of exogenous DNA damage, and lethality is a consequence of dysfunctional mitosis proceeding in the presence of unprocessed HJs. Thus, GEN1 activity cannot be substituted for the SLX4-associated nucleases, and one of the HJ resolvase activities, either of those associated with SLX4 or with GEN1, is required for cell viability, even in the presence of BLM. In vivo HJ resolution depends on both SLX4-associated MUS81-EME1 and SLX1, suggesting that they are acting in concert in the context of SLX4. Graphical abstract Teaser The requirements for Holliday junction (HJ) processing in human mitotic cells are now dissected by Smogorzewska and colleagues. The authors demonstrate that nuclease-mediated resolution of HJs, provided by SLX4-associated nucleases and GEN1, is a requirement for cell viability rather than a backup pathway for nonnucleolytic dissolution. When HJs do not get processed, dramatic chromosomal abnormalities appear and cells cannot complete division. The study also finds that two SLX4-associated nucleases, MUS81-EME1 and SLX1, are necessary for HJ resolution.

Description: Publication date: Available online 29 September 2013 Source: FEBS Open Bio Author(s): Chantel N. Jensen , Sohail T. Ali , Michael J. Allen , Gideon Grogan The flavoprotein monooxygenase (FPMO) from Stenotrophomonas maltophilia (SMFMO, Uniprot: B2FLR2) catalyses the asymmetric oxidation of thioethers and is unusual amongst FPMOs in its ability to use the non-phosphorylated cofactor NADH, as well as NADPH, for the reduction of the FAD coenzyme. In order to explore the basis for cofactor promiscuity, structure-guided mutation of two residues in the cofactor binding site, Gln193 and His194, in SMFMO were performed in an attempt to imitate the cofactor binding site of the NADPH-dependent FMO from Methylophaga aminisulfidivorans sp. SK1 (mFMO), in which structurally homologous residues Arg234 and Thr235 bind the NADPH 2’-ribose phosphate. Mutation of His194 to threonine proved most significant, with a switch in specificity from NADH to NADPH [( k cat / K m NADH)/ k cat / K m NADPH) from 1.5:1 to 1:3.5, mostly as a result of a reduced K m for NADPH of approximately seven-fold in the His194Thr mutant. The structure of the Gln193Arg/His194Thr mutant revealed no substantial changes in the backbone of the enzyme or orientation of side chains resulting from mutation. Mutation of Phe52, in the vicinity of FAD, and which in mFMO is an asparagine thought to be responsible for flavin hydroperoxide stabilisation, is, in SMFMO, a determinant of enantioselectivity in sulfoxidation. Mutation of Phe52 to valine resulted in a mutant that transformed para -tolyl methyl sulfide into the ( S )-sulfoxide with 32% e.e., compared to 25% ( R )- for the wild type. These results shed further light both on the cofactor specificity of FPMOs, and their determinants of enantioselectivity, with a view to informing engineering studies of FPMOs in the future.

Description: Publication date: Available online 30 September 2013 Source: FEBS Open Bio Author(s): Yoshichika Taira , Yuki Okegawa , Kazuhiko Sugimoto , Masato Abe , Hideto Miyoshi , Toshiharu Shikanai Antimycin A 3 (AA) is used as an inhibitor of cyclic electron transport around photosystem I. However, the high concentrations of AA that are needed for inhibition have secondary effects, even in chloroplasts. Here, we screened for chemicals that inhibited ferredoxin-dependent plastoquinone reduction in ruptured chloroplasts at lower concentrations than those required for AA. We identified two AA-like compounds: AAL1 and AAL2. AAL1 likely shares an inhibitory site with AA, most probably in the PGR5–PGRL1 protein complex, and enhances O 2 evolution in photosystem II, most likely via an uncoupler-like effect. AAL1 and AAL2 are unlikely to penetrate intact leaves. In ruptured chloroplasts, AALs are superior to AA as inhibitors of cyclic electron transport.

Description: Haiping Tian, Shaoqiong Yang, and Lu Cheng et al. Experiments were conducted in a water tunnel by tomographic time-resolved particle image velocimetry (Tomo-TRPIV). The Reynolds number Reθ is 2 460 on the base of momentum thickness. According to the physical mechanism of the stretch and compression of multi-scale vortex structures in the wall-bou ... [Theor. Appl. Mech. Lett. 3 , 052002 (2013)] published Tue Sep 10, 2013 .

Description: Junjie Sheng, Hualing Chen, and Lei Liu et al. Viscoelasticity and temperature can significantly affect the performance of a dielectric elastomer. In the current study, we use a thermodynamic model to describe the effect of temperature and viscoelasticity on the electromechanical response undergoing a cyclic electric load by taking into accoun ... [Theor. Appl. Mech. Lett. 3 , 054005 (2013)] published Tue Sep 10, 2013 .

Description: Fengchao Wang and Hengan Wu Spreading of nanofluids on solid substrate was studied via molecular dynamics simulations. Simulation models for two immiscible fluids (oil and water based nanofluids) confined in a slit between two planar solid walls were set up. The influence of the volume concentration of the nanoparticles on t ... [Theor. Appl. Mech. Lett. 3 , 054006 (2013)] published Tue Sep 10, 2013 .

Description: Xiang He, Pengfei Wang, and Guoyou Huang et al. Indentation is a simple and nondestructive method to measure the mechanical properties of soft materials, such as hydrogels, elastomers and soft tissues. In this work, we have developed a micro-indentation system with high-precision to measure the mechanical properties of soft materials, where the ... [Theor. Appl. Mech. Lett. 3 , 054004 (2013)] published Tue Sep 10, 2013 .

Description: Junshi Zhang, Hualing Chen, and Junjie Sheng et al. In this paper, we present a modified model describing the constitutive relation of viscoelastic dielectric elastomer (DE). The uniform uniaxial tension-recovery experiment was carried out at different stretching rates. Based on Yeoh hyper-elastic model, model-fitting approach is put forward to obt ... [Theor. Appl. Mech. Lett. 3 , 054011 (2013)] published Tue Sep 10, 2013 .

Description: Yugang Tang, Ying Liu, and Qingshan Yang Considering the effects of osmotic pressure, elastic bending, Maxwell pressure, surface tension, as well as flexo-electric and dielectric properties of phospholipid membrane, the shape equation for sphere vesicle in alternation (AC) electric field is derived based on the liquid crystal model by mi ... [Theor. Appl. Mech. Lett. 3 , 054010 (2013)] published Tue Sep 10, 2013 .

Description: Jianying Hu, Yuhao He, and Jincheng Lei et al. In periodic cellular structures, novel pattern transformations are triggered by a reversible elastic instability under the axial compression. Based on the deformation-triggered new pattern, periodic cellular structures can achieve special mechanical properties. In this paper, the designed architec ... [Theor. Appl. Mech. Lett. 3 , 054007 (2013)] published Tue Sep 10, 2013 .

Description: Abdessattar Abdelkefi and Mehdi Ghommem Wing flapping and morphing can be very beneficial to managing the weight of micro air vehicles through coupling the aerodynamic forces with stability and control. In this letter, harvesting energy from the wing morphing is studied to power cameras, sensors, or communication devices of micro air ve ... [Theor. Appl. Mech. Lett. 3 , 052004 (2013)] published Tue Sep 10, 2013 .

Description: Shabram Sadeghi Esfahlani, Hassan Shirvani, and Sunny Nwaubani et al. Structural optimization for crashworthiness criteria is of particular significance especially at early stage of design. The comparative study of Kriging and radial basis function network (RBFN) was performed in order to improve the crashworthiness effects of honeycomb. Improving the crashworthines ... [Theor. Appl. Mech. Lett. 3 , 031002 (2013)] published Fri May 10, 2013 .

Description: Guyue Jiao and Ruojing Zhang The erythrocytes play an important role in the human body. The healthy erythrocytes can undergo extremely large deformation while passing through small capillaries. Their infection by Malaria Plasmodium falcipurum (P.f.) will lead to capillary blockage and blood flow obstruction. Many experimental ... [Theor. Appl. Mech. Lett. 3 , 034001 (2013)] published Fri May 10, 2013 .

Description: Su Yean Teh, Hock Lye Koh, and Donald L. DeAngelis et al. Predicting potential changes in groundwater salinity in low-lying coastal regions due to climate change is important, where coastal vegetation is abundant, succession competition between halophytes and glycophytes plays a significant role in the salinity budget. Sea level rise enhances salinity in ... [Theor. Appl. Mech. Lett. 3 , 032001 (2013)] published Fri May 10, 2013 .

Description: Publication date: Available online 6 June 2013 Source: Cell Reports Author(s): Guillaume Diss , Alexandre K. Dubé , Joël Boutin , Isabelle Gagnon-Arsenault , Christian R. Landry Cells contain many important protein complexes involved in performing and regulating structural, metabolic, and signaling functions. One major challenge in cell biology is to elucidate the organization and mechanisms of robustness of these complexes in vivo. We developed a systematic approach to study structural dependencies within complexes in living cells by deleting subunits and measuring pairwise interactions among other components. We used our methodology to perturb two conserved eukaryotic complexes: the retromer and the nuclear pore complex. Our results identify subunits that are critical for the assembly of these complexes, reveal their structural architecture and uncover…, and uncover mechanisms by which protein interactions are modulated. Our results also show that paralogous proteins play a key role in the robustness of protein complexes and shape their assembly landscape. Our approach paves the way for studying the response of protein interactomes to mutations and enhances our understanding of genotype-phenotype maps. Graphical abstract

Description: Publication date: Available online 6 June 2013 Source: Cell Reports Author(s): Christopher R. Faehnle , Elad Elkayam , Astrid D. Haase , Gregory J. Hannon , Leemor Joshua-Tor Argonautes are the central protein component in small RNA silencing pathways. Of the four human Argonautes (hAgo1–hAgo4) only hAgo2 is an active slicer. We determined the structure of hAgo1 bound to endogenous copurified RNAs to 1.75 Å resolution and hAgo1 loaded with let-7 microRNA to 2.1 Å. Both structures are strikingly similar to the structures of hAgo2. A conserved catalytic tetrad within the PIWI domain of hAgo2 is required for its slicing activity. Completion of the tetrad, combined with a mutation on a loop adjacent to the active site of hAgo1, results in slicer activity that is substantially enhanced by swapping in the N domain of hAgo2. hAgo3, with an intact tetrad, becomes an active slicer by swapping the N domain of hAgo2 without additional mutations. Intriguingly, the elements that make Argonaute an active slicer involve a sophisticated interplay between the active site and more distant regions of the enzyme. Graphical abstract

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Quanxi Zhang , Jingjing Tian , Yunlong Bai , Zhenhua Yang , Huifang Zhang , Ziqiang Meng The present study was designed to investigate the mechanisms underlying the effects of SO2 on functions of the isolated perfused hearts in rats. The results suggest that both SO2 and SO2 derivatives (sulfite: bisulfite, 3:1, M/M) elicited a negative inotropic effect. At high concentrations, the effects of SO2 or its derivatives on heart functions might be related to the increasing of reactive oxygen species (ROS) contents and decreasing of ATPase activities as well as the potentially damaging effects on the hearts; while at low concentrations, SO2 or its derivatives might modulate heart functions mainly through the NO signal transduction pathway.

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Lei Li , Xinqiang Shen , Yunlong Wang , Hang Jiang , Mei Jiang The toxicity effects of Alexandriurn minuturn and Gymnodiniurn on the embryonic development of Sparus macrocephalus were tested through the toxicological experiments about hatching spawns and developing larvae of Sparus macrocephalus . Alexandriurn minuturn and Gymnodiniurn solution was diluted into three groups (about 3000cell/ml, 1500cell/ml, 500cell/ml). The results showed that the hatch of the spawns was sensitive to both kinds of the algae. And the toxicity results from Alexandriurn minuturn were inferior to that from Gymnodiniurn . The test of larvae 96-LC50 showed that, larvae was more susceptible to the Gymnodiniurn and produced certain resistance to the toxicity of the algae. Both the Alexandriurn minuturn and Gymnodiniurn restrained body length and weight increase as well as ATPase and GSH-PX enzyme activities of the larvae, while restrain from Gymnodiniurn was stronger. In conclusion, the effects on growth and development of Sparus macrocephalus spawns and larvae resulted from Gymnodiniurn was much higher than that from Alexandriurn minuturn .

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Xiaodong Ding , Shirong Zhang , Shuyi Li , Xinrong Liao , Rongping Wang To test the hypothesis that exogenous silicon (Si) would mediate the detoxification of Chromium (Cr) on pakchoi ( Brassica Chinensis L.) growing in Cr-contaminated soil, a pot experiment that 0, 50, 100 and 200 mg·kg -1 Cr (Na 2 Cr 2 O 7 2H 2 O) were supplied to soil together with 0, 0.5, 1.0 and 1.5 g·kg-1 Si (Na2SiO3) for 48 days, was studied. Results showed that supplying Si improved the growth of pakchoi in low Cr level. However, the shoot dry weight decreased with the increasing Si supplied in high Cr level. Compared with under non-Cr stress, the application of Si significantly increased the activities of POD, SOD and CAT of pakchoi under excess Cr. However, antioxidant enzymes activities displayed no difference under three Cr levels supplied. Shoot Cr accumulation decreased, while root Cr concentration increased, which was ascribed to the formation of precipitation-bound, “organic matter bound” Cr and the reduction of exchangeable-bound Cr fractions in the soil. Furthermore, the rhizosphere soil pH increased with Si level under either Cr level, suggesting that exogenous Si would induce the alkalization in the rhizosphere mediated detoxification of Cr on pakchoi by promoting the formation of precipitation-bound, organic matter bound Cr in Cr-contaminated soil, thereby probably decreasing Cr uptake from Cr-contaminated soil. These results proved direct evidence that Si played a mediated role, which decreased Cr uptake and improved the stabilization of Cr in Cr- contaminated soil.

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Shuyi Li , Shirong Zhang , Xiaodong Ding , Xinrong Liao , Rongping Wang A field experiment of foliar application of silicon sol, cerium sol and silicon-cerium composite sol of different concentrations on Lettuce in field mildly combined Cd/Pb contaminated soil, was conducted to study effects of the application on yield, quality, antioxidant enzymes (SOD, POD) activities and Cd/Pb absorption, and hence to determine optimum concentration of the silicon sols and cerium sols to be sprayed for relieving toxicity of Cd/Pb. Results showed that spraying silicon and cerium sols could promote growth of Lettuce, increase contents of vitamin C and soluble sugar, and reduce nitrite content, enhance activities of SOD and POD, and inhibit the absorption of Cd/Pb and decrease the content and accumulation of Cd/Pb in shoots and roots, and reduce the risk of Cd/Pb to human body through food chain, while spraying silicon-cerium composite sol of 0.50 g·kg -1 silicon sols (SiO2) and 0.20 g·kg -1 cerium sols (CeO 2 ) was the most significant in effect.

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Fayun Li , Guoqiang Wu , Shui Hu , Zhiping Fan , Qun Gao The negative effect of deicing salt on surface water have been reported by a number of studies, but there is a lack of knowledge about the effects of deicing salt on the growth behavior and the change of biochemical composition of algal Chlorella vulgaris ( C. vulgaris ). Algal were cultured at different concentration of deicing salt, algal cell densities, chlorophyll (a), protein and polysaccharides contents were measured. The results of this work showed that deicing salt had statistically significant inhibitory effects ( P 〈0.01) on the cell growth of algae, and the best-fit predictive equation of algal cell densities ( D algal, algal cells m/l) versus concentration of deicing salt ( C salt, g/l) after 7- day culture in this experiment was presented as a quadratic equation with C salt being the independent variable and D algal being the dependent variable (R 2 =0.944, P 〈0.01). The contents of chlorophyll (a) in C. vulgaris cell exposed to different concentrations of deicing salt suggested that the chlorophyll (a) content significantly decreased ( P 〈0.05) with the concentration of deicing salt higher than 4 g/l. Deicing salts also caused the trend of proteins contents decrease in C. vulgaris cells, and significantly increased ( P 〈0.05) the contents of polysaccharides in algae cell at 2 g/l deicing salt, however, the change of that was not significantly affected at deicing salt concentrations higher than 2 g/l.

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Zhenhua Yang , Yuexia Zhang , Quanxi Zhang , Tianxing Pei , Ziqiang Meng A number of studies on sulfur dioxide (SO 2 ) in toxicology and pharmacology have been reported, however spectral properties of SO 2 and its derivatives were seldom investigated. We investigated the absorption spectra of SO 2 , sodium sulfite (Na 2 SO 3 ), sodium bisulfite (NaHSO3) and sodium metabisulfite (Na 2 S 2 O 5 ) in aqueous solution. In the meanwhile, the effects of HCl on spectral properties of SO 2 and its derivatives were also investigated. We found that gaseous SO 2 in ethanol, n-butyl-alcohol and glycerol had a characteristic absorption peak at 276 nm. Na 2 S 2 O 5 and NaHSO 3 exhibited an absorption peak at 257 nm. Absorption of SO 2 at 276 nm was strongly enhanced in the presence of HCl. NaHSO3, Na 2 SO 3 and Na 2 S 2 O 5 also exhibited absorption at 276 nm with the addition of HCl, which was enhanced with the increase of HCl concentration. Importantly, two conclusions have been reached on the basis of our results. First, we attributed the absorbing power of SO 2 to SO 2 molecule, rather than hydrated sulfur dioxide. Second, absorption of SO 2 strongly enhanced by HCl at 276 nm was due to H + , instead of the formation of a complex SO 2 Cl-. Primary studies also indicated that NaHSO 3 and Na 2 S 2 O5 with HCl had a similar effect as SO 2 did in rat thoracic aortic rings, which prompted us believe that NaHSO3 and Na2S2O5 with HCl may be acted as a donor of SO2 in biology and other area.

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Yuexia Zhang , Zhenhua Yang , Dan Guo , Hong Geng , Chuan Dong In the study, we present the results of thermodynamic simulation of CaSO4 water-salt systems containing Ca 2+ , Mg 2+ , Na + , K + and HCO - 3 at 37°C. The results showed that the solubility of CaSO phase increased with increasing NaCl as wells as KCl concentration in the range of 0.0 to 2.0 M and 0.0 to 1.0 M, respectively. Remarkably, enhanced effect of MgCl 2 on the solubility of CaSO 4 phase was much larger than that of KCl or NaCl. The only exception was CaCl 2 , which was found to reduce solubility value of CaSO4 in aqueous solution at 37°C with the increase of CaCl 2 concentration. Also, the solubility of CaSO4 phase in mixed salt solutions was investigated at 37°C. The common ion effect was the main factor on the solubility of CaSO 4 in the mixed salts solution. Furthermore, CaSO 4 solubility was reduced by small amounts of NaHCO 3 in mixed solutions. These studies are of relevance in the estimating the changes of various salts in blood plasma and production of salt with low impurities of Ca2+ and SO 4 2- ions, as well as estimating oceanic-containing CaSO 4 uptake of CO 2 .

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Huimin Zhao , Hongtao Wang , Xie Quan , Feng Tan Tetracycline (TC), a widely used broad spectrum antibiotic, is excreted to environment seriously. Because of its harmful effects, it is essential to establish an effective method for TC determintation. In this work, we fabricated an electrochemical sensor for TC detection based on molecularly imprinted technique. The molecularly imprinted polymer was thermalpolymerized on Ti substrate electrodeposited with micro-nano Pt cluster (MIP-Pt/Ti). The linear range was in a TC concentration range from 0.1 to 10 mg L-1, and the detection limit was 0.026 mg L-1 (S/N = 3). The current change of TC on MIP-Pt/Ti electrode was 10 and 14 times than that of CTC and CAP, respectively. The results indicated that this electrochemical sensor exhibited good sensitivity and selectivity for TC.

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Hongbo Xu , Wanping Zhang , Xiaoshun Zhang , Jing Wang , Jian Wang A new cloud point extraction procedure was established for the simultaneous preconcentration and determination of cobalt(II), nickel(II), and copper(II) ions in water samples. After complexation with 2-(5-bromo-2-pyridylazo)-5- (diethylamino) phenol (5-Br-PADAP), the analytes could be competitively extracted in a surfactant octylphenoxy polyethoxyethanol (TritonX-114), prior to determination by flame atomic absorption spectrometry (FAAS). The effects of pH, the concentrations of chelating agent and surfactant, equilibration temperature and time, sample volume, etc on CPE were studied. The preconcentration factor obtained was 25 and the limits of detection (DL) obtained for cobalt(II), nickel(II), and copper(II) were 2.4, 1.7 and 1.5 ng·mL−1, respectively. Standard reference material of poplar leaf (GBW 07604) was analyzed by the proposed methods, giving results of cobalt(II), nickel(II), and copper(II) found contents in consistency with the standard values. The presented preconcentration procedure was successfully applied to determination cobalt(II), nickel(II), and copper(II) in water samples.

Description: Publication date: 2013 Source: Procedia Environmental Sciences, Volume 18 Author(s): Duanping Xu , Changjian Gu , Xiao Chen Humic acid (HA) was isolated from lignite. Flocculent HA was made and used to adsorb and remove dye acid red 3R from aqueous solution. The adsorption experiments were carried out in a batch process to observe the effect of various parameters such as contact time, dose of flocculent HA, ionic strength (NaCl) as well as adsorption kinetics and isotherm. Results showed that adsorption of acid red 3R on flocculent HA could reach equilibrium at less than 180 min. The adsorption kinetics obeyed the pseudo-second order model (R2=0.994). The adsorption was described with Freundlich equation on the basis of value of regression coefficient (R2=0.984). The removal rate of the dye increased with the increase of the dose of flocculent HA, while it decreased with the addition of NaCl in the aqueous solution. These suggested that the adsorption mechanism was the electrostatic attraction, to form hydrogen bonds, and van der waals’ force between molecules of HA and acid red 3R. Conclusion was made that flocculent HA isolated from lignite could be used as an adsorbent to remove the dye from aqueous solution.