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Rxivist combines preprints from bioRxiv with data from Twitter to help you find the papers being discussed in your field. Currently indexing 54,857 bioRxiv papers from 253,274 authors.

Most downloaded bioRxiv papers, since beginning of last month

51,431 results found. For more information, click each entry to expand.

541: Pericentromeric hypomethylation elicits an interferon response in an animal model of ICF syndrome
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Posted to bioRxiv 23 Aug 2018

Pericentromeric hypomethylation elicits an interferon response in an animal model of ICF syndrome
191 downloads molecular biology

Srivarsha Rajshekar, Jun Yao, Paige K Arnold, Sara G Payne, Yinwen Zhang, Teresa V Bowman, Robert J Schmitz, John R Edwards, Mary G Goll

Pericentromeric satellite repeats are enriched in 5-methylcytosine (5mC). Loss of 5mC at these sequences is common in cancer and is a hallmark of Immunodeficiency, Centromere and Facial abnormalities (ICF) syndrome. While the general importance of 5mC is well-established, the specific functions of 5mC at pericentromeres are less clear. To address this deficiency, we generated a viable animal model of pericentromeric hypomethylation through mutation of the ICF-gene ZBTB24. Deletion of zebrafish zbtb24 caused a progressive loss of 5mC at pericentromeres and ICF-like phenotypes. Hypomethylation of these repeats triggered derepression of pericentromeric transcripts and activation of an interferon-based innate immune response. Injection of pericentromeric RNA is sufficient to elicit this response in wild-type embryos, and mutation of the MDA5-MAVS dsRNA-sensing machinery blocks the response in mutants. These findings identify activation of the innate immune system as an early consequence of pericentromeric hypomethylation, implicating derepression of pericentromeric transcripts as a trigger of autoimmunity.

542: Monogenic and polygenic inheritance become instruments for clonal selection
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Posted to bioRxiv 29 May 2019

Monogenic and polygenic inheritance become instruments for clonal selection
191 downloads genetics

Po-Ru Loh, Giulio Genovese, Steven A McCarroll

Clonally expanded blood cells with somatic mutations (clonal hematopoiesis, CH) are commonly acquired with age and increase risk of later blood cancer. To identify genes and mutations that give selective advantage to mutant clones, we identified among 482,789 UK Biobank participants some 19,632 autosomal mosaic chromosomal alterations (mCAs), including deletions, duplications, and copy number-neutral loss of heterozygosity (CNN-LOH). Analysis of these acquired mutations, along with inherited genetic variation, revealed 52 inherited, rare, large-effect coding or splice variants (in seven genes) that greatly (odds ratios of 11 to 758) increased vulnerability to CH with specific acquired CNN-LOH mutations. Acquired mutations systematically replaced the inherited risk alleles (at MPL ) or duplicated them to the homologous chromosome (at FH , NBN , MRE11 , ATM , SH2B3 , and TM2D3 ). Three of the seven genes ( MRE11 , NBN , and ATM ) encode components of the MRN-ATM pathway, which limits cell division after DNA damage and telomere attrition; another two ( MPL , SH2B3 ) encode proteins that regulate stem cell self-renewal. In addition to these monogenic inherited forms of CH, we found a common and surprisingly polygenic form: CNN-LOH mutations across the genome tended to cause chromosomal segments with alleles that promote hematopoietic cell proliferation to replace their homologous (allelic) counterparts, increasing polygenic drive for blood-cell proliferation traits. This dynamic reveals a challenge for lifelong cytopoiesis in any genetically diverse species: individuals inherit unequal proliferative genetic potentials on paternally and maternally derived chromosome-pairs, and readily-acquired mutations that replace chromosomal segments with their homologous counterparts give selective advantage to mutant cells.

543: Structural variants identified by Oxford Nanopore PromethION sequencing of the human genome
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Posted to bioRxiv 03 Oct 2018

Structural variants identified by Oxford Nanopore PromethION sequencing of the human genome
191 downloads bioinformatics

Wouter De Coster, Arne De Roeck, Tim De Pooter, Svenn D'Hert, Peter De Rijk, Mojca Strazisar, Kristel Sleegers, Christine Van Broeckhoven

We sequenced the Yoruban NA19240 genome on the Oxford Nanopore PromethION for benchmarking and evaluation of recently published aligners and structural variant calling tools. In this work, we determined the precision and recall, present high confidence and high sensitivity call sets of variants and discuss optimal parameters. The aligner Minimap2 and structural variant caller Sniffles are both the most accurate and the most computationally efficient tools in our study. We describe our scalable workflow for identification, annotation, and characterization of tens of thousands of structural variants from long read genome sequencing of an individual or population. By discussing the results of this genome we provide an approximation of what can be expected in future long read sequencing studies aiming for structural variant identification.

544: Genomic loci susceptible to systematic sequencing bias in clinical whole genomes
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Posted to bioRxiv 22 Jun 2019

Genomic loci susceptible to systematic sequencing bias in clinical whole genomes
191 downloads bioinformatics

Timothy M Freeman, Genomics England Research Consortium, Dennis Wang, Jason Harris

Background Highly accurate next-generation sequencing (NGS) of genetic variants is key to many areas of science and medicine, such as cataloguing population genetic variation and diagnosing patients with genetic diseases. Certain genomic loci and regions can be prone to higher rates of systematic sequencing and alignment bias that pose a challenge to achieving high accuracy, resulting in false positive variant calls. Current standard practices to differentiate between loci that can and cannot be sequenced with high confidence utilise consensus between different sequencing methods as a proxy for sequencing confidence. This assumption is not accurate in cases where all sequencing pipelines have consensus on the same errors due to similar systematic biases in sequencing. Alternative methods are therefore required to identify systematic biases. Methods We have developed a novel statistical method based on summarising sequenced reads from whole genome clinical samples and cataloguing them in “Incremental Databases” (IncDBs) that maintain individual confidentiality. Variant statistics were analysed and catalogued for each genomic position that consistently showed systematic biases with the corresponding sequencing pipeline. Results We have demonstrated that systematic errors in NGS data are widespread, with persistent low-fraction alleles present at 1.26-2.43% of the human autosomal genome across three different Illumina-based pipelines, each consisting of at least 150 patient samples. We have identified a variety of genomic regions that are more or less prone to systematic biases, such as GC-rich regions (OR = 6.47-8.19) and the NIST high-confidence genomic regions (OR = 0.154-0.191). We have verified our predictions on a gold-standard reference genome and have shown that these systematic biases can lead to suspect variant calls at clinically important loci, including within introns and exons. Conclusions Our results recommend increased caution to minimise the effect of systematic biases in whole genome sequencing and alignment. This study supports the utility of a statistical approach to enhance quality control of clinically sequenced samples in order to flag up variant calls made at known suspect loci for further analysis or exclusion, using anonymised summary databases from which individual patients cannot be re-identified, so that results can be shared more widely. * BAM : Binary Alignment Map (file format) BED : Browser Extensible Data (file format) cfDNA : Cell-free DNA ctDNA : Circulating tumour DNA GIAB : Genome in a Bottle (consortium) gnomAD : Genome Aggregation Database IGV : Integrative Genomics Viewer (software tool) IncDB : Incremental Database MC : Monte-Carlo NGS : Next-Generation Sequencing NIST : National Institute of Standards and Technology (organisation) SD : Standard Deviation SNPs : Single-Nucleotide Polymorphism SNVs : Single-Nucleotide Variant WGS : Whole-Genome Sequencing

545: Single-cell RNA sequencing reveals a dynamic stromal niche within the evolving tumour microenvironment
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Posted to bioRxiv 09 Nov 2018

Single-cell RNA sequencing reveals a dynamic stromal niche within the evolving tumour microenvironment
191 downloads cancer biology

Sarah Davidson, Mirjana Efremova, Angela Riedel, Bidesh Mahata, Jhuma Pramanik, Jani Huuhtanen, Gozde Kar, Roser Vento-Tormo, Tzachi Hagai, Xi Chen, Muzlifah A. Haniffa, Jacqueline D. Shields, Sarah A Teichmann

Non-cancerous stromal cells represent a highly diverse compartment of the tumour, yet their role across tumour evolution remains unclear. We employed single-cell RNA sequencing to determine stromal adaptations in murine melanoma at different points of tumour development. Naive lymphocytes recruited from lymph nodes underwent activation and clonal expansion within the tumour, prior to PD1 and Lag3 expression, while tumour-associated myeloid cells promoted the formation of a suppressive niche through cytokine secretion and inhibitory T cell interactions. We identified three temporally distinct cancer-associated fibroblast (CAF) populations displaying unique signatures, and verified these in human datasets. In early tumours, immune CXCL12/CSF1 and complement-expressing CAFs supported recruitment of macrophages, whereas contractile CAFs became more prevalent in later tumours. This study highlights the complex interplay and increasing diversity among cells that co-evolve with the tumour, indicating that from early stages of development, stromal cells acquire the capacity to modulate the immune landscape towards suppression.

546: Dynamic patterns of transcript abundance of transposable element families in maize
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Posted to bioRxiv 12 Jun 2019

Dynamic patterns of transcript abundance of transposable element families in maize
191 downloads genomics

Sarah N Anderson, Michelle C Stitzer, Peng Zhou, Jeffrey Ross-Ibarra, Cory D. Hirsch, Nathan M Springer

Transposable Elements (TEs) are mobile elements that contribute the majority of DNA sequences in the maize genome. Due to their repetitive nature, genomic studies of TEs are complicated by the difficulty of properly attributing multi-mapped short reads to specific genomic loci. Here, we utilize a method to attribute RNA-seq reads to TE families rather than particular loci in order to characterize transcript abundance for TE families in the maize genome. We applied this method to assess per-family expression of transposable elements in >800 published RNA-seq libraries representing a range of maize development, genotypes, and hybrids. While a relatively small proportion of TE families are transcribed, expression is highly dynamic with most families exhibiting tissue-specific expression. A large number of TE families were specifically detected in pollen and endosperm, consistent with reproductive dynamics that maintain silencing of TEs in the germ line. We find that B73 transcript abundance is a poor predictor of TE expression in other genotypes and that transcript levels can differ even for shared TEs. Finally, by assessing recombinant inbred line and hybrid transcriptomes, complex patterns of TE transcript abundance across genotypes emerged. Taken together, this study reveals a dynamic contribution of TEs to maize transcriptomes.

547: On the adaptive behavior of head-fixed flies navigating in two-dimensional, visual virtual reality
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Posted to bioRxiv 04 Nov 2018

On the adaptive behavior of head-fixed flies navigating in two-dimensional, visual virtual reality
191 downloads animal behavior and cognition

Hannah Haberkern, Melanie A. Basnak, Biafra Ahanonu, David Schauder, Jeremy D. Cohen, Mark Bolstad, Christopher Bruns, Vivek Jayaraman

A navigating animal's sensory experience is shaped not just by its surroundings, but by its movements within them, which in turn are influenced by its past experiences. Studying the intertwined roles of sensation, experience and directed action in navigation has been made easier by the development of virtual reality (VR) environments for head-fixed animals, which allow for quantitative measurements of behavior in well-controlled sensory conditions. VR has long featured in studies of Drosophila melanogaster, but these experiments have typically relied on one-dimensional (1D) VR, effectively allowing the fly to change only its heading in a visual scene, and not its position. Here we explore how flies navigate in a two-dimensional (2D) visual VR environment that more closely resembles their experience during free behavior. We show that flies' interaction with landmarks in 2D environments cannot be automatically derived from their behavior in simpler 1D environments. Using a novel paradigm, we then demonstrate that flies in 2D VR adapt their behavior in a visual environment in response to optogenetically delivered appetitive and aversive stimuli. Much like free-walking flies after encounters with food, head-fixed flies respond to optogenetic activation of sugar-sensing neurons by initiating a local search behavior. Finally, by pairing optogenetic activation of heat-sensing cells to the flies' presence near visual landmarks of specific shapes, we elicit selective learned avoidance of landmarks associated with aversive "virtual heat". These head-fixed paradigms set the stage for an interrogation of fly brain circuitry underlying flexible navigation in complex visual environments.

548: CRISPR-TSKO facilitates efficient cell type-, tissue-, or organ-specific mutagenesis in Arabidopsis
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Posted to bioRxiv 20 Nov 2018

CRISPR-TSKO facilitates efficient cell type-, tissue-, or organ-specific mutagenesis in Arabidopsis
191 downloads plant biology

Ward Decaestecker, Rafael Andrade Buono, Marie L. Pfeiffer, Nick Vangheluwe, Joris Jourquin, Mansour Karimi, Gert Van Isterdael, Tom Beeckman, Moritz K. Nowack, Thomas B. B. Jacobs

Detailed functional analyses of many fundamentally-important plant genes via conventional loss-of-function approaches are impeded by severe pleiotropic phenotypes. In particular, mutations in genes that are required for basic cellular functions and/or reproduction often interfere with the generation of homozygous mutant plants, precluding further functional studies. To overcome this limitation, we devised a CRISPR-based tissue-specific knockout system, CRISPR-TSKO, enabling the generation of somatic mutations in particular plant cell types, tissues, and organs. In Arabidopsis, CRISPR-TSKO mutations in essential genes caused well-defined, localized phenotypes in the root cap, stomatal lineage, or entire lateral roots. The underlying modular cloning system allows for efficient selection, identification, and functional analysis of mutant lines directly in the first transgenic generation. The efficacy of CRISPR-TSKO opens new avenues to discover and analyze gene functions in spatial and temporal contexts of plant life while avoiding pleiotropic effects of system-wide loss of gene function.

549: Exploiting regulatory heterogeneity to systematically identify enhancers with high accuracy
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Posted to bioRxiv 18 Jan 2018

Exploiting regulatory heterogeneity to systematically identify enhancers with high accuracy
191 downloads genomics

Hamutal Arbel, William W. Fisher, Ann S. Hammonds, Kenneth H. Wan, Soo Park, Richard Weiszmann, Soile Keränen, Clara Henriquez, Omid Shams Solari, Peter Bickel, Mark D. Biggin, Susan E Celniker, James B Brown

Identifying functional enhancers elements in metazoan systems is a major challenge. For example, large-scale validation of enhancers predicted by ENCODE reveal false positive rates of at least 70%. Here we use the pregrastrula patterning network of Drosophila melanogaster to demonstrate that loss in accuracy in held out data results from heterogeneity of functional signatures in enhancer elements. We show that two classes of enhancer are active during early Drosophila embryogenesis and that by focusing on a single, relatively homogeneous class of elements, over 98% prediction accuracy can be achieved in a balanced, completely held-out test set. The class of well predicted elements is composed predominantly of enhancers driving multi-stage, segmentation patterns, which we designate segmentation driving enhancers (SDE). Prediction is driven by the DNA occupancy of early developmental transcription factors, with almost no additional power derived from histone modifications. We further show that improved accuracy is not a property of a particular prediction method: after conditioning on the SDE set, naive Bayes and logistic regression perform as well as more sophisticated tools. Applying this method to a genome-wide scan, we predict 1,640 SDEs that cover 1.6% of the genome, 916 of which are novel. An analysis of 32 novel SDEs using wholemount embryonic imaging of stably integrated reporter constructs chosen throughout our prediction rank-list showed >90% drove expression patterns. We achieved 86.7% precision on a genome-wide scan, with an estimated recall of at least 98%, indicating high accuracy and completeness in annotating this class of functional elements.

550: Promoters adopt distinct dynamic manifestations depending on transcription factor context
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Posted to bioRxiv 26 May 2019

Promoters adopt distinct dynamic manifestations depending on transcription factor context
190 downloads systems biology

Anders Sejr Hansen, Christoph Zechner

Cells respond to external signals and stresses by activating transcription factors (TF), which induce gene expression changes. Previous work suggests that signal-specific gene expression changes are partly achieved because different gene promoters exhibit varying induction dynamics in response to the same TF input signal. Here, using high-throughput quantitative single-cell measurements and a novel statistical method, we systematically analyzed transcription in individual cells to a large number of dynamic TF inputs. In particular, we quantified the scaling behavior among different transcriptional features extracted from the measured trajectories such as the gene activation delay or duration of promoter activity. Surprisingly, we found that even the same gene promoter can exhibit qualitatively distinct induction and scaling behaviors when exposed to different dynamic TF contexts. That is, promoters can adopt context-dependent 'manifestations'. Our analysis suggests that the full complexity of signal processing by genetic circuits may be significantly underestimated when studied in specific contexts only.

551: High Throughput pMHC-I Tetramer Library Production Using Chaperone Mediated Peptide Exchange
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Posted to bioRxiv 30 May 2019

High Throughput pMHC-I Tetramer Library Production Using Chaperone Mediated Peptide Exchange
190 downloads immunology

Sarah A Overall, Jugmohit S Toor, Stephanie Hao, Mark Yarmarkovich, Son Nguyen, Alberto S Japp, Danai Moschidi, Michael R Betts, John M. Maris, Peter Smibert, Nikolaos G Sgourakis

Peptide exchange technologies are essential for the generation of pMHC-multimer libraries, used to probe highly diverse, polyclonal TCR repertoires. Using the molecular chaperone TAPBPR, we present a robust method for the capture of stable, empty MHC-I molecules which can be readily tetramerized and loaded with peptides of choice in a high-throughput manner. Combined with tetramer barcoding using multi-modal cellular indexing technology (ECCITE-seq), our approach allows a combined analysis of TCR repertoires and other T-cell transcription profiles together with their cognate pMHC-I specificities in a single experiment.

552: The role of multilevel selection in host microbiome evolution
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Posted to bioRxiv 06 Jun 2019

The role of multilevel selection in host microbiome evolution
190 downloads evolutionary biology

Simon van Vliet, Michael Doebeli

Animals are associated with a microbiome that can affect their reproductive success. It is therefore important to understand how a host and its microbiome coevolve. According to the hologenome concept, hosts and their microbiome form an integrated evolutionary entity, a holobiont, on which selection can potentially act directly. However, this view is controversial and there is an active debate on whether the association between hosts and their microbiomes is strong enough to allow for selection at the holobiont level. Much of this debate is based on verbal arguments, but a quantitative framework is needed to investigate the conditions under which selection can act at the holobiont level. Here we use multilevel selection theory to develop such a framework. We found that selection at the holobiont level can in principle favor a trait that is costly to the microbes but that provides a benefit to the host. However, such scenarios require rather stringent conditions. The degree to which microbiome composition is heritable decays with time, and selection can only act at the holobiont level when this decay is slow enough, which occurs when vertical transmission is stronger than horizontal transmission. Moreover, the host generation time has to be short enough compared to the timescale of the evolutionary dynamics at the microbe level. Our framework thus allows us to quantitatively predict for what kind of systems selection could act at the holobiont level.

553: Consistent metagenome-derived metrics verify and define bacterial species boundaries
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Posted to bioRxiv 24 May 2019

Consistent metagenome-derived metrics verify and define bacterial species boundaries
190 downloads microbiology

Matthew R Olm, Alexander Crits-Christoph, Spencer Diamond, Adi Lavy, Paula B. Matheus Carnevali, Jillian F Banfield

Longstanding questions relate to the existence of naturally distinct bacterial species and genetic approaches to distinguish them. Bacterial genomes in public databases form distinct groups, but these databases are subject to isolation and deposition biases. We compared 5,203 bacterial genomes from 1,457 environmental metagenomic samples to test for distinct clouds of diversity, and evaluated metrics that could be used to define the species boundary. Bacterial genomes from the human gut, soil, and the ocean all exhibited gaps in whole-genome average nucleotide identities (ANI) near the previously suggested species threshold of 95% ANI. While genome-wide ratios of non-synonymous and synonymous nucleotide differences (dN/dS) decrease until ANI values approach ~98%, estimates for homologous recombination approached zero at ~95% ANI, supporting breakdown of recombination due to sequence divergence as a species-forming force. We evaluated 107 genome-based metrics for their ability to distinguish species when full genomes are not recovered. Full length 16S rRNA genes were least useful because they were under-recovered from metagenomes, but many ribosomal proteins displayed both high metagenomic recoverability and species-discrimination power. Taken together, our results verify the existence of sequence-discrete microbial species in metagenome-derived genomes and highlight the usefulness of ribosomal genes for gene-level species discrimination.

554: Bright split red fluorescent proteins with enhanced complementation efficiency for the tagging of endogenous proteins and visualization of synapses
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Posted to bioRxiv 25 Oct 2018

Bright split red fluorescent proteins with enhanced complementation efficiency for the tagging of endogenous proteins and visualization of synapses
190 downloads cell biology

Siyu Feng, Aruna Varshney, Doris Coto Villa, Cyrus Modavi, John Kohler, Fatima Farah, Nebat Ali, Joachim D Mueller, Miri VanHoven, Bo Huang

Self-associating split fluorescent proteins (FPs) have been widely used for labeling proteins, scaffolding protein assembly and detecting cell-cell contacts. Newly developed self-associating split FPs, however, have suffered from suboptimal fluorescence signal. Here, by investigating the complementation process, we have demonstrated two approaches to improve split FPs: assistance through SpyTag/SpyCatcher interaction and directed evolution. The latter has yielded two split sfCherry3 variants with substantially enhanced overall brightness, facilitating the tagging of endogenous proteins by gene editing. Based on sfCherry3, we have further developed a new red-colored trans-synaptic marker called Neuroligin-1 sfCherry3 Linker Across Synaptic Partners (NLG-1 CLASP) for multiplexed visualization of neuronal synapses in living animals, demonstrating its broad applications.

555: Chd1 regulates repair of promoter-proximal DNA breaks to sustain hypertranscription in embryonic stem cells
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Posted to bioRxiv 04 Jun 2019

Chd1 regulates repair of promoter-proximal DNA breaks to sustain hypertranscription in embryonic stem cells
190 downloads molecular biology

Aydan Bulut-Karslioglu, Hu Jin, Marcela Guzman-Ayala, Andrew JK Williamson, Miroslav Hejna, Anthony D Whetton, Jun S. Song, Miguel Ramalho-Santos

Stem and progenitor cells undergo a global elevation of nascent transcription, or hypertranscription, during key developmental transitions involving rapid cell proliferation. The chromatin remodeler Chd1 binds to genes transcribed by RNA Polymerase (Pol) I and II and is required for hypertranscription in embryonic stem (ES) cells in vitro and the early post- implantation epiblast in vivo. Biochemically, Chd1 has been shown to facilitate transcription at least in part by removing nucleosomal barriers to elongation, but its mechanism of action in stem cells remains poorly understood. Here we report a novel role for Chd1 in the repair of promoter- proximal endogenous double-stranded DNA breaks (DSBs) in ES cells. An unbiased proteomics approach revealed that Chd1 interacts with several DNA repair factors including Atm, Parp1, Kap1 and Topoisomerase 2b. We show that wild-type ES cells display high levels of phosphorylated H2A.X and Kap1 at chromatin, notably at rDNA in the nucleolus, in a Chd1-dependent manner. Loss of Chd1 leads to an extensive accumulation of DSBs at Chd1- bound Pol II-transcribed genes and rDNA. Genes prone to DNA breaks in Chd1 KO ES cells tend to be longer genes with GC-rich promoters, a more labile nucleosomal structure and roles in chromatin regulation, transcription and signaling. These results reveal a vulnerability of hypertranscribing stem cells to endogenous DNA breaks, with important implications for developmental and cancer biology.

556: Neural trajectories in the supplementary motor area and primary motor cortex exhibit distinct geometries, compatible with different classes of computation
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Posted to bioRxiv 24 May 2019

Neural trajectories in the supplementary motor area and primary motor cortex exhibit distinct geometries, compatible with different classes of computation
190 downloads neuroscience

Abigail Russo, Ramin Khajeh, Sean R Bittner, Sean M Perkins, John P Cunningham, Laurence F Abbott, Mark M. Churchland

The supplementary motor area (SMA) is believed to contribute to higher-order aspects of motor control. To examine this contribution, we employed a novel cycling task and leveraged an emerging strategy: testing whether population trajectories possess properties necessary for a hypothesized class of computations. We found that, at the single-neuron level, SMA exhibited multiple response features absent in M1. We hypothesized that these diverse features might contribute, at the population level, to avoidance of 'population trajectory divergence' - ensuring that two trajectories never followed the same path before separating. Trajectory divergence was indeed avoided in SMA but not in M1. Network simulations confirmed that low trajectory divergence is necessary when guidance of future action depends upon internally tracking contextual factors. Furthermore, the empirical trajectory geometry - helical in SMA versus elliptical in M1 - was naturally reproduced by networks that did, versus did not, internally track context.

557: An introduced crop plant is driving diversification of the virulent bacterial pathogen Erwinia tracheiphila
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Posted to bioRxiv 12 Jun 2018

An introduced crop plant is driving diversification of the virulent bacterial pathogen Erwinia tracheiphila
190 downloads evolutionary biology

Lori R Shapiro, Joseph Nathaniel Paulson, Brian J Arnold, Erin D Scully, Olga Zhaxybayeva, Naomi Pierce, Jorge Rocha, Vanja Klepac-Ceraj, Kristina Holton, Roberto Kolter

Erwinia tracheiphila is the causal agent of bacterial wilt of cucurbits, an economically important phytopathogen affecting few cultivated Cucurbitaceae host plant species in temperate Eastern North America. However, essentially nothing is known about E. tracheiphila population structure or genetic diversity. To address this shortcoming, a representative collection of 88 E. tracheiphila isolates was gathered from throughout its geographic range, and their genomes were sequenced. Phylogenomic analysis revealed three genetic clusters with distinct hrpT3SS virulence gene repertoires, host plant association patterns, and geographic distributions. The low genetic variation within each cluster suggests a recent population bottleneck followed by population expansion. We showed that in the field and greenhouse, cucumber (Cucumis sativus), which was introduced to North America by early Spanish conquistadors, is the most susceptible host plant species, and the only species susceptible to isolates from all three lineages. The establishment of large agricultural populations of highly susceptible C. sativus in temperate Eastern North America may have facilitated the original emergence of E. tracheiphila into cucurbit agro-ecosystems, and this introduced plant species may now be acting as a highly susceptible reservoir host. Our findings have broad implications for agricultural sustainability by drawing attention to how worldwide crop plant movement, agricultural intensification and locally unique environments may affect the emergence, evolution, and epidemic persistence of virulent microbial pathogens.

558: Structural basis of p62/SQSTM1 helical filaments, their presence in p62 bodies and role in cargo recognition in the cell
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Posted to bioRxiv 14 Jun 2019

Structural basis of p62/SQSTM1 helical filaments, their presence in p62 bodies and role in cargo recognition in the cell
190 downloads molecular biology

Arjen Jakobi, Stefan T. Huber, Simon A. Mortensen, Sebastian W Schultz, Anthimi Palara, Tanja Kuhm, Birendra K. Shrestha, Trond Larmark, Wim J.H. Hagen, Matthias Wilmanns, Terje Johansen, Andreas Brech, Carsten Sachse

p62/SQSTM1 is an autophagy receptor and signaling adaptor with an N-terminal PB1 domain that forms the scaffold of phase-separated p62 bodies in the cell. The molecular determinants that govern PB1 domain filament formation in vitro remain to be determined and the role of p62 filaments inside the cell is currently unclear. We determined four high-resolution cryo-EM structures of different human and Arabidopsis PB1 domain assemblies and observed a filamentous ultrastructure of phase-separated p62/SQSTM1 bodies using correlative cellular EM. We show that oligomerization or polymerization, driven by a double arginine finger in the PB1 domain, is a general requirement for lysosomal targeting of p62. Furthermore, the filamentous assembly state of p62 is required for autophagosomal processing of the p62-specific cargo KEAP1. Our results show that using such mechanisms, p62 filaments can be critical for cargo recognition and are an integral part of phase separated p62 bodies.

559: Jomon genome sheds light on East Asian population history
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Posted to bioRxiv 15 Mar 2019

Jomon genome sheds light on East Asian population history
189 downloads genomics

Takashi Gakuhari, Shigeki Nakagome, Simon Rasumussen, Morten Allentoft, Takehiro Sato, Thorfinn Korneliussen, Blanaid Ni Chuinneagain, Hiromi Matsumae, Kae Koganebuchi, Ryan Schmidt, Souichiro Mizushima, Osamu Kondo, Nobuo Shigehara, Minoru Yoneda, Ryosuke Kimura, Hajime Ishida, Yoshiyuki Masuyama, Yasuhiro Yamada, Atsushi Tajima, Hiroki Shibata, Atsushi Toyoda, Toshiyuki Tsurumoto, Tetsuaki Wakebe, Hiromi Shitara, Tsunehiko Hanihara, Eske Willerslev, Martin Sikora, Hiroki Oota

Anatomical modern humans reached East Asia by >40,000 years ago (kya). However, key questions still remain elusive with regard to the route(s) and the number of wave(s) in the dispersal into East Eurasia. Ancient genomes at the edge of East Eurasia may shed light on the detail picture of peopling to East Eurasia. Here, we analyze the whole-genome sequence of a 2.5 kya individual (IK002) characterized with a typical Jomon culture that started in the Japanese archipelago >16 kya. The phylogenetic analyses support multiple waves of migration, with IK002 forming a lineage basal to the rest of the ancient/present-day East Eurasians examined, likely to represent some of the earliest-wave migrants who went north toward East Asia from Southeast Asia. Furthermore, IK002 has the extra genetic affinity with the indigenous Taiwan aborigines, which may support a coastal route of the Jomon-ancestry migration from Southeast Asia to the Japanese archipelago. This study highlight the power of ancient genomics with the isolated population to provide new insights into complex history in East Eurasia.

560: Positively Selected Enhancer Elements Endow Tumor Cells with Metastatic Competence
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Posted to bioRxiv 25 Jun 2017

Positively Selected Enhancer Elements Endow Tumor Cells with Metastatic Competence
189 downloads cancer biology

James J. Morrow, Ian Bayles, Alister Funnell, Tyler Miller, Alina Saiakhova, Michael Lizardo, Cynthia Bartels, Maaike Kapteijn, Stevephen Hung, Arnulfo Mendoza, Daniel Chee, Jay Myers, Frederick Allen, Marco Gambarotti, Alberto Righi, Analisa DiFeo, Brian Rubin, Alex Huang, Paul Meltzer, Lee Helman, Piero Picci, Henri Versteeg, John Stamatoyannopoulos, Chand Khanna, Peter Scacheri

Metastasis results from a complex set of traits acquired by tumor cells, distinct from those necessary for tumorigenesis. Here, we investigate the contribution of enhancer elements to the metastatic phenotype of osteosarcoma. Through epigenomic profiling, we identify substantial differences in enhancer activity between primary and metastatic tumors in human patients as well as near isogenic pairs of high and low lung-metastatic osteosarcoma cells. We term these regions Metastatic Variant Enhancer Loci (Met-VELs). We demonstrate that these Met-VELs drive coordinated waves of gene expression during metastatic colonization of the lung. Met-VELs cluster non-randomly, indicating that activity of these enhancers and their associated gene targets are positively selected. As evidence of this causal association, osteosarcoma lung metastasis is inhibited by global interruptions of Met-VEL-associated gene expression via pharmacologic BET inhibition, by knockdown of AP-1 transcription factors that occupy Met-VELs, and by knockdown or functional inhibition of individual genes activated by Met-VELs, such as F3. We further show that genetic deletion of a single Met-VEL at the F3 locus blocks metastatic cell outgrowth in the lung. These findings indicate that Met-VELs and the genes they regulate play a functional role in metastasis and may be suitable targets for anti-metastatic therapies.

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