Rxivist logo

Rxivist combines preprints from bioRxiv with data from Twitter to help you find the papers being discussed in your field. Currently indexing 48,092 bioRxiv papers from 215,637 authors.

Most tweeted bioRxiv papers, last 24 hours

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

41: All-optical electrophysiology reveals excitation, inhibition, and neuromodulation in cortical layer 1
more details view paper

Posted to bioRxiv 23 Apr 2019

All-optical electrophysiology reveals excitation, inhibition, and neuromodulation in cortical layer 1
9 tweets neuroscience

Linlin Z. Fan, Simon Kheifets, Urs L. Boehm, Kiryl D. Piatkevich, Hao Wu, Vicente Parot, Michael Xie, Edward S Boyden, Anne E. Takesian, Adam E Cohen

The stability of neural dynamics arises through a tight coupling of excitatory (E) and inhibitory (I) signals. Genetically encoded voltage indicators (GEVIs) can report both spikes and subthreshold dynamics in vivo, but voltage alone only reveals the combined effects of E and I synaptic inputs, not their separate contributions individually. Here we combine optical recording of membrane voltage with simultaneous optogenetic manipulation to probe E and I individually in barrel cortex Layer 1 (L1) neurons in awake mice. Our studies show that L1 neurons integrate thalamocortical excitation and lateral inhibition to produce precisely timed responses to whisker stimuli. Top-down neuromodulatory inputs drive additional excitation in L1. Together, these results suggest a model for computation in L1 consistent with its hypothesized role in attentional gating of the underlying cortex.

42: Fast and interpretable alternative splicing and differential gene-level expression analysis using transcriptome segmentation with Yanagi
more details view paper

Posted to bioRxiv 08 Jul 2018

Fast and interpretable alternative splicing and differential gene-level expression analysis using transcriptome segmentation with Yanagi
9 tweets bioinformatics

Mohamed K Gunady, Steve Mount, Hector Corrada Bravo

Introduction: Analysis of differential alternative splicing from RNA-seq data is complicated by the fact that many RNA-seq reads map to multiple transcripts, besides, the annotated transcripts are often a small subset of the possible transcripts of a gene. Here we describe Yanagi, a tool for segmenting transcriptome to create a library of maximal L-disjoint segments from a complete transcriptome annotation. That segment library preserves all transcriptome substrings of length L and transcripts structural relationships while eliminating unnecessary sequence duplications. Contributions: In this paper, we formalize the concept of transcriptome segmentation and propose an efficient algorithm for generating segment libraries based on a length parameter dependent on specific RNA-Seq library construction. The resulting segment sequences can be used with pseudo-alignment tools to quantify expression at the segment level. We characterize the segment libraries for the reference transcriptomes of Drosophila melanogaster and Homo sapiens and provide gene-level visualization of the segments for better interpretability. Then we demonstrate the use of segments-level quantification into gene expression and alternative splicing analysis. The notion of transcript segmentation as introduced here and implemented in Yanagi opens the door for the application of lightweight, ultra-fast pseudo-alignment algorithms in a wide variety of RNA-seq analyses. Conclusion: Using segment library rather than the standard transcriptome succeeds in significantly reducing ambigious alignments where reads are multimapped to several sequences in the reference. That allowed avoiding the quantification step required by standard kmer-based pipelines for gene expression analysis. Moreover, using segment counts as statistics for alternative splicing analysis enables achieving comparable performance to counting-based approaches (e.g. rMATS) while rather using fast and lighthweight pseudo alignment.

43: Disrupted basal ganglia–thalamocortical loops in focal to bilateral tonic-clonic seizures
more details view paper

Posted to bioRxiv 24 Apr 2019

Disrupted basal ganglia–thalamocortical loops in focal to bilateral tonic-clonic seizures
8 tweets neuroscience

Xiaosong He, Ganne Chaitanya, Burcu Asma, Danielle S. Bassett, Joseph I Tracy, Michael R Sperling

Focal to bilateral tonic-clonic seizures are associated with lower quality of life, higher risk of seizure-related injuries, increased chance of sudden unexpected death, as well as unfavorable treatment outcomes. Achieving greater understanding of its underlying circuitry offers better opportunity to control these particularly serious seizures. Towards this goal, we provide a network science perspective of the interactive pathways among basal ganglia, thalamus and the cortex, to explore the imprinting of secondary seizure generalization on the mesoscale brain network in temporal lobe epilepsy. Specifically, we parameterized the functional organization of both the thalamocortical network and the basal ganglia–thalamus network with resting-state functional magnetic resonance imaging in three groups of patients with different focal to bilateral tonic-clonic seizure histories. Using the participation coefficient to describe the pattern of thalamocortical connections among different cortical networks, we showed that, compared to patients with no previous history, those with positive histories of focal to bilateral tonic-clonic seizures, including both remote (none for over one year) and current (within the past year) histories, presented more uniform distribution patterns of thalamocortical connections in the ipsilateral medial-dorsal thalamic nuclei. As a sign of greater thalamus mediated cortico-cortical communication, this result comports with greater susceptibility to secondary seizure generalization from the epileptogenic temporal lobe to broader brain networks in these patients. Using interregional integration to characterize the functional interaction between basal ganglia and thalamus, we demonstrated that patients with current history presented increased interaction between putamen and globus pallidus internus, and decreased interaction between the latter and the thalamus, compared to the other two patient groups. Importantly, through a series of "disconnection" simulations, we showed that these changes in interactive profiles of the basal ganglia--thalamus network in the current history group mainly depended upon the direct but not the indirect basal ganglia pathway. It is intuitively plausible that such disruption in the striatum modulated tonic inhibition of the thalamus from the globus pallidus internus could lead to an under-suppressed thalamus, which in turn may account for their greater vulnerability to secondary seizure generalization. Collectively, these findings suggest that the broken balance between the basal ganglia inhibition and thalamus synchronization can inform the presence and effective control of focal to bilateral tonic-clonic seizures. The mechanistic underpinnings we uncover may shed light on the development of new treatment strategies for patients with epilepsy.

44: Cell-type specific innervation of cortical pyramidal cells at their apical tufts
more details view paper

Posted to bioRxiv 15 Mar 2019

Cell-type specific innervation of cortical pyramidal cells at their apical tufts
8 tweets neuroscience

Ali Karimi, Jan Odenthal, Florian Drawitsch, Kevin Michael Boergens, Moritz Helmstaedter

We investigated the synaptic innervation of apical tufts of cortical pyramidal cells in a region between layers 1 and 2 using 3-D electron microscopy (3D-EM) applied to four cortical regions in mouse. Across all cortices, we found the relative inhibitory input at the apical dendrite's main bifurcation to be more than 3-fold stronger for layer 2 pyramidal cells than for all other pyramidal cells. Towards the distal tuft dendrites in upper layer 1, however, the relative inhibitory input was about 2-fold stronger for L5 pyramidal cells than for all others. Only L3 pyramidal cells showed homogeneous inhibitory input density. The inhibitory to excitatory synaptic balance is thus specific for the types of pyramidal cells. Inhibitory axons preferentially innervated either layer 2 or L3/5 apical dendrites, but not both. These findings describe connectomic principles for the control of pyramidal cells at their apical dendrites in the upper layers of the cerebral cortex and point to differential computational properties of layer 2, layer 3 and layer 5 pyramidal cells in cortex.

45: Effects of compassion training on brain responses to suffering others
more details view paper

Posted to bioRxiv 23 Apr 2019

Effects of compassion training on brain responses to suffering others
8 tweets neuroscience

Yoni Ashar, JESSICA ANDREWS-HANNA, Joan Halifax, SONA DIMIDJIAN, Tor D. Wager

What are the active ingredients and brain mechanisms of compassion training? To address these questions, we conducted a three-armed randomized trial (N = 57) of compassion meditation (CM). We compared a four-week CM program delivered by smartphone application to i) a placebo condition, in which participants inhaled sham oxytocin, which they were told would enhance compassion, and ii) a familiarity control condition, designed to control for increased familiarity with suffering others. Functional MRI was collected while participants listened to narratives describing suffering others at pre- and post-intervention. CM increased brain responses to suffering others in the medial orbitofrontal cortex (mOFC) relative to both the placebo and familiarity control conditions, and in the nucleus accumbens relative to the familiarity control condition. Results support the specific efficacy of CM beyond effects of expectancy, demand characteristics, and increased familiarity with suffering others, and implicate affective and motivational pathways as brain mechanisms of CM.

46: A revised model for promoter competition based on multi-way chromatin interactions
more details view paper

Posted to bioRxiv 17 Apr 2019

A revised model for promoter competition based on multi-way chromatin interactions
8 tweets genomics

Aukje Marieke Oudelaar, Caroline L. Harrold, Lars L.P. Hanssen, Jelena M Telenius, Douglas R Higgs, Jim R Hughes

Specific communication between gene promoters and enhancers is critical for accurate regulation of gene expression. However, it remains unclear how specific interactions between multiple regulatory elements and genes contained within a single chromatin domain are coordinated. Recent technological advances allow for the investigation of multi-way chromatin interactions at single alleles in individual nuclei. This can provide insights into how multiple regulatory elements cooperate or compete for transcriptional activation. We have used these techniques in a mouse model in which the α-globin domain is extended to include several additional genes. This allows us to determine how the interactions of the α-globin super-enhancer are distributed between multiple promoters in a single domain. Our data show that gene promoters do not form mutually exclusive interactions with the super-enhancer, but all interact simultaneously in a single complex. These finding show that promoters within the same domain do not structurally compete for interactions with enhancers, but form a regulatory hub structure, consistent with the recent model of transcriptional activation in phase-separated nuclear condensates.

47: Report of Partial findings from the National Toxicology Program Carcinogenesis Studies of Cell Phone Radiofrequency Radiation in Hsd: Sprague Dawley® SD rats (Whole Body Exposure)
more details view paper

Posted to bioRxiv 26 May 2016

Report of Partial findings from the National Toxicology Program Carcinogenesis Studies of Cell Phone Radiofrequency Radiation in Hsd: Sprague Dawley® SD rats (Whole Body Exposure)
7 tweets cancer biology

Michael Wyde, Mark Cesta, Chad Blystone, Susan Elmore, Paul Foster, Michelle Hooth, Grace Kissling, David Malarkey, Robert Sills, Matthew Stout, Nigel Walker, Kristine Witt, Mary Wolfe, John Bucher

The U.S. National Toxicology Program (NTP) has carried out extensive rodent toxicology and carcinogenesis studies of radiofrequency radiation (RFR) at frequencies and modulations used in the U.S. telecommunications industry. This report presents partial findings from these studies. The occurrences of two tumor types in male Harlan Sprague Dawley rats exposed to RFR, malignant gliomas in the brain and schwannomas of the heart, were considered of particular interest and are the subject of this report. The findings in this report were reviewed by expert peer reviewers selected by the NTP and National Institutes of Health (NIH). These reviews and responses to comments are included as appendices to this report, and revisions to the current document have incorporated and addressed these comments. When the studies are completed, they will undergo additional peer review before publication in full as part of the NTP's Toxicology and Carcinogenesis Technical Reports Series. No portion of this work has been submitted for publication in a scientific journal. Supplemental information in the form of four additional manuscripts has or will soon be submitted for publication. These manuscripts describe in detail the designs and performance of the RFR exposure system, the dosimetry of RFR exposures in rats and mice, the results to a series of pilot studies establishing the ability of the animals to thermoregulate during RFR exposures, and studies of DNA damage. (1) Capstick M, Kuster N, Kuhn S, Berdinas-Torres V, Wilson P, Ladbury J, Koepke G, McCormick D, Gauger J, and Melnick R. A radio frequency radiation reverberation chamber exposure system for rodents; (2) Yijian G, Capstick M, McCormick D, Gauger J, Horn T, Wilson P, Melnick RL, and Kuster N. Life time dosimetric assessment for mice and rats exposed to cell phone radiation; (3) Wyde ME, Horn TL, Capstick M, Ladbury J, Koepke G, Wilson P, Stout MD, Kuster N, Melnick R, Bucher JR, and McCormick D. Pilot studies of the National Toxicology Program's cell phone radiofrequency radiation reverberation chamber exposure system; (4) Smith-Roe SL, Wyde ME, Stout MD, Winters J, Hobbs CA, Shepard KG, Green A, Kissling GE, Tice RR, Bucher JR, and Witt KL. Evaluation of the genotoxicity of cell phone radiofrequency radiation in male and female rats and mice following subchronic exposure.

48: pathwayPCA: an R package for integrative pathway analysis with modern PCA methodology and gene selection
more details view paper

Posted to bioRxiv 22 Apr 2019

pathwayPCA: an R package for integrative pathway analysis with modern PCA methodology and gene selection
7 tweets bioinformatics

Gabriel Odom, Yuguang Ban, Lizhong Liu, Xiaodian Sun, Alexander R Pico, Bing Zhang, Lily Wang, Xi Chen

With the advance in high-throughput technology for molecular assays, multi-omics datasets have become increasingly available. However, most currently available pathway analysis software provide little or no functionalities for analyzing multiple types of -omics data simultaneously. In addition, most tools do not provide sample-specific estimates of pathway activities, which are important for precision medicine. To address these challenges, we present pathwayPCA, a unique R package for integrative pathway analysis that utilizes modern statistical methodology including supervised PCA and adaptive elastic-net PCA for principal component analysis. pathwayPCA can analyze continuous, binary, and survival outcomes in studies with multiple covariate and/or interaction effects. We provide three case studies to illustrate pathway analysis with gene selection, integrative analysis of multi-omics datasets to identify driver genes, estimating and visualizing sample-specific pathway activities in ovarian cancer, and identifying sex-specific pathway effects in kidney cancer. pathwayPCA is an open source R package, freely available to the research community. We expect pathwayPCA to be a useful tool for empowering the wide scientific community on the analyses and interpretation of the wealth of multi-omics data recently made available by TCGA, CPTAC and other large consortiums.

49: Single-molecule turnover dynamics of actin and membrane coat proteins in clathrin-mediated endocytosis
more details view paper

Posted to bioRxiv 24 Apr 2019

Single-molecule turnover dynamics of actin and membrane coat proteins in clathrin-mediated endocytosis
7 tweets cell biology

Michael M. Lacy, David Baddeley, Julien Berro

Actin is required for clathrin-mediated endocytosis (CME) in yeast. Experimental observations indicate that this actin assembly generates force to deform the membrane and overcome the cell's high turgor pressure, but the precise molecular details remain unresolved. Based on previous models, we predicted that actin at endocytic sites continually polymerize and disassemble, turning over multiple times during an endocytic event. Here we applied single-molecule speckle tracking in live fission yeast to directly measure this predicted turnover within the CME assembly for the first time. In contrast with the overall ~20-sec lifetimes of actin and actin-associated proteins in endocytic patches, we detected single-molecule residence times around 1 to 2 sec, and high turnover rates of membrane-associated proteins in CME. Furthermore, we find heterogeneous behaviors in many proteins' motions. These results indicate that rapid and continuous turnover is a key feature of the endocytic machinery and suggest revising quantitative models of force production.

50: Comparison of long-read sequencing technologies in the hybrid assembly of complex bacterial genomes
more details view paper

Posted to bioRxiv 26 Jan 2019

Comparison of long-read sequencing technologies in the hybrid assembly of complex bacterial genomes
7 tweets bioinformatics

Nicola De Maio, Liam P. Shaw, Alasdair Hubbard, Sophie George, Nick Sanderson, Jeremy Swann, Ryan Wick, Manal AbuOun, Emma Stubberfield, Sarah J Hoosdally, Derrick W Crook, Timothy E. A. Peto, Anna E Sheppard, Mark J. Bailey, Daniel S Read, Muna F. Anjum, A Sarah Walker, Nicole Stoesser, The REHAB consortium

Illumina sequencing allows rapid, cheap and accurate whole genome bacterial analyses, but short reads (<300 bp) do not usually enable complete genome assembly. Long read sequencing greatly assists with resolving complex bacterial genomes, particularly when combined with short-read Illumina data (hybrid assembly); however, it is not clear how different long-read sequencing methods impact on assembly accuracy. Relative automation of the assembly process is also crucial to facilitating high-throughput complete bacterial genome reconstruction, avoiding multiple bespoke filtering and data manipulation steps. In this study, we compared hybrid assemblies for 20 bacterial isolates, including two reference strains, using Illumina sequencing and long reads from either Oxford Nanopore Technologies (ONT) or from SMRT Pacific Biosciences (PacBio) sequencing platforms. We chose isolates from the Enterobacteriaceae family, as these frequently have highly plastic, repetitive genetic structures and complete genome reconstruction for these species is relevant for a precise understanding of the epidemiology of antimicrobial resistance. We de novo assembled genomes using the hybrid assembler Unicycler and compared different read processing strategies. Both strategies facilitate high-quality genome reconstruction. Combining ONT and Illumina reads fully resolved most genomes without additional manual steps, and at a lower cost per isolate in our setting. Automated hybrid assembly is a powerful tool for complete and accurate bacterial genome assembly.

51: Agreement between two large pan-cancer CRISPR-Cas9 gene dependency datasets
more details view paper

Posted to bioRxiv 10 Apr 2019

Agreement between two large pan-cancer CRISPR-Cas9 gene dependency datasets
6 tweets cancer biology

Joshua M Dempster, Clare Pacini, Sasha Pantel, Fiona M Behan, Thomas Green, John Krill-Burger, Charlotte M Beaver, Victor Zhivich, Hanna Najgebauer, Felicity Allen, Emanuel Gonçalves, Rebecca Shepherd, John G. Doench, Kosuke Yusa, Francisca Vazquez, Leopold Parts, Jesse S Boehm, Todd R. Golub, William C Hahn, David E Root, Matthew J Garnett, Francesco Iorio, Aviad Tsherniak

Genome-scale CRISPR-Cas9 viability screens performed in cancer cell lines provide a systematic approach to identify cancer dependencies and new therapeutic targets. As multiple large-scale screens become available, a formal assessment of the reproducibility of these experiments becomes necessary. Here we analyzed data from recently published pan-cancer CRISPR-Cas9 screens performed at the Broad and Sanger institutes. Despite numerous experimental differences, we found that the screen results are highly concordant across multiple metrics in that both common and specific dependencies were identified in cell lines jointly. Strong biomarkers of gene dependency found in one institute are recovered in the other. Through further analysis and replication experiments at each institute, we found that batch effects are driven principally by two key experimental parameters: the reagent library and the assay lengths employed in the two studies. These observations and analyses show that Broad and Sanger CRISPR-Cas9 viability screens produce robust and reproducible findings.

52: Solution of the FISH-Hi-C paradox for Human Interphase Chromosomes
more details view paper

Posted to bioRxiv 21 Apr 2019

Solution of the FISH-Hi-C paradox for Human Interphase Chromosomes
6 tweets biophysics

Dave Thirumalai, Guang Shi

Hi-C experiments are used to infer the contact probabilities between loci separated by varying genome lengths. Contact probability should decrease as the spatial distance between two loci increases. However, studies comparing Hi-C and FISH data show that in some cases the distance between one pair of loci, with larger Hi-C readout, is paradoxically larger compared to another pair with a smaller value of the contact probability. We solve the FISH-Hi-C paradox using a theory based on a Generalized Rouse Model for Chromosomes (GRMC). The FISH-Hi-C paradox arises because the cell population is highly heterogeneous, which means that a given contact is present in only a fraction, η, of cells. Insights from the GRMC is used to construct a theory, without any adjustable parameters, to extract the distribution of subpopulations from the FISH data, which quantitatively reproduces the Hi-C data. Heterogeneity is pervasive in genome organization at all length scales, reflecting large cell-to-cell variations.

53: The Vc2 cyclic di-GMP dependent riboswitch of Vibrio cholerae regulates expression of an upstream small RNA by controlling RNA stability
more details view paper

Posted to bioRxiv 24 Apr 2019

The Vc2 cyclic di-GMP dependent riboswitch of Vibrio cholerae regulates expression of an upstream small RNA by controlling RNA stability
6 tweets microbiology

Benjamin R Pursley, Christopher M. Waters

Cyclic di-GMP (c-di-GMP) is a bacterial second messenger molecule that is important in the biology of Vibrio cholerae, but the molecular mechanisms by which this molecule regulates downstream phenotypes have not been fully characterized. We have previously shown that the Vc2 c-di-GMP-binding riboswitch, encoded upstream of the gene tfoY, functions as an off-switch in response to c-di-GMP. However, the mechanism by which c-di-GMP controls expression of tfoY has not been fully elucidated.  During our studies of this mechanism, we determined that c-di-GMP binding to Vc2 also controls the abundance and stability of upstream non-coding small RNAs (sRNA) with 3’-ends located immediately downstream of the Vc2 riboswitch. Our results suggest these sRNAs are not generated by transcriptional termination but rather by preventing degradation of the upstream untranslated RNA when c-di-GMP is bound to Vc2.

54: A novel uncultured marine cyanophage lineage with lysogenic potential linked to a putative marine Synechococcus 'relic' prophage
more details view paper

Posted to bioRxiv 17 May 2018

A novel uncultured marine cyanophage lineage with lysogenic potential linked to a putative marine Synechococcus 'relic' prophage
6 tweets microbiology

José Flores-Uribe, Alon Philosof, Itai Sharon, Svetlana Fridman, Shirley Larom, Oded Beja

Marine cyanobacteria are important contributors to primary production in the ocean and their viruses (cyanophages) affect the ocean microbial communities. Despite reports of lysogeny in marine cyanobacteria, the genome sequence of such temperate cyanophages remains unknown although genomic analysis indicate potential for lysogeny in certain marine cyanophages. Using assemblies from Red Sea and Tara Oceans metagenomes, we recovered genomes of a novel uncultured marine cyanophage lineage, which contain, in addition to common cyanophage genes, a phycobilisome degradation protein NblA, an integrase and a split DNA polymerase. The DNA polymerase forms a monophyletic clade with a DNA polymerase from a genomic island in Synechococcus WH8016. The island contains a relic prophage that does not resemble any previously reported cyanophage but shares several genes with the newly identified cyanophages reported here. Metagenomic recruitment indicates that the novel cyanophages are widespread, albeit at low abundance. Here we describe a novel potentially lysogenic cyanophage family, their abundance and distribution in the marine environment.

55: Consistent alterations of human fecal microbes after transplanted to germ-free mice
more details view paper

Posted to bioRxiv 13 Dec 2018

Consistent alterations of human fecal microbes after transplanted to germ-free mice
6 tweets bioinformatics

Yanze Li, Wenming Cao, Na L Gao, Xing-Ming Zhao, Wei-Hua Chen

Fecal microbiota transplant (FMT) of human fecal samples to germ-free (GF) mice is useful for establishing causal relationships between altered gut microbiota and human phenotypes. However, due to intrinsic differences between human and mouse intestines, and distinct diets of choice between the two organisms, replicating human phenotypes in mouse through FMT is not guaranteed; similarly, treatments that are effective in mouse models do not guarantee their success in human either. In this study, we aimed to identify human gut microbes that have undergone significant and consistent changes after transplanted to GF mice across multiple experimental settings. By comparing gut microbiota profiles in 1,713 human-mouse pairs, we found strikingly on average <50% of the human gut microbes can be re-established in mice at the species level; among which, more than 1/3 have undergone significant changes (referred as to 'variable microbes'), most of which were consistent across multiple human-mouse pairs and experimental settings. Consistently, one-third of human samples had changed their enterotypes, i.e. significant changes in their leading species after FMT. Mice fed with controlled diet showed significant decrease in the enterotype change rate (~25%) as compared those with non-controlled diet (~50%), suggesting a possible solution for rescue. Strikingly, most of the variable microbes have been implicated in human diseases, with some being recognized as causing species. Our results highlighted the challenges of using mouse model in replicating human gut microbiota-associated phenotypes, provided useful information for researchers using mice in their gut microbiota studies and call for additional validations after FMT.

56: Gene regulatory network reconstruction incorporating 3D chromosomal architecture reveals key transcription factors and DNA elements driving neural lineage commitment
more details view paper

Posted to bioRxiv 18 Apr 2018

Gene regulatory network reconstruction incorporating 3D chromosomal architecture reveals key transcription factors and DNA elements driving neural lineage commitment
6 tweets molecular biology

Valeriya Malysheva, Marco Antonio Mendoza-Parra, Matthias Blum, Mikhail Spivakov, Hinrich Gronemeyer

Lineage commitment is a fundamental process that enables the morphogenesis of multicellular organisms from a single pluripotent cell. While many genes involved in the commitment to specific lineages are known, the logic of their joint action is incompletely understood, and predicting the effects of genetic perturbations on lineage commitment is still challenging. Here, we devised a gene regulatory network analysis approach, GRN-loop, to identify key cis-regulatory DNA elements and transcription factors that drive lineage commitment. GRN-loop is based on signal propagation and combines transcription factor binding data with the temporal profiles of gene expression, chromatin state and 3D chromosomal architecture. Applying GRN-loop to a model of morphogen-induced early neural lineage commitment, we discovered a set of driver transcription factors and enhancers, some of them validated in recent data and others hitherto unknown. Our work provides the basis for an integrated understanding of neural lineage commitment, and demonstrates the potential of gene regulatory network analyses informed by 3D chromatin architecture to uncover the key genes and regulatory elements driving developmental processes.

57: Ancient genomes from southern Africa pushes modern human divergence beyond 260,000 years ago
more details view paper

Posted to bioRxiv 05 Jun 2017

Ancient genomes from southern Africa pushes modern human divergence beyond 260,000 years ago
6 tweets evolutionary biology

Carina M Schlebusch, Helena Malmström, Torsten Günther, Per Sjödin, Alexandra Coutinho, Hanna Edlund, Arielle R Munters, Maryna Steyn, Himla Soodyall, Marlize Lombard, Mattias Jakobsson

Southern Africa is consistently placed as one of the potential regions for the evolution of Homo sapiens. To examine the region's human prehistory prior to the arrival of migrants from East and West Africa or Eurasia in the last 1,700 years, we generated and analyzed genome sequence data from seven ancient individuals from KwaZulu-Natal, South Africa. Three Stone Age hunter-gatherers date to ~2,000 years ago, and we show that they were related to current-day southern San groups such as the Karretjie People. Four Iron Age farmers (300-500 years old) have genetic signatures similar to present day Bantu-speakers. The genome sequence (13x coverage) of a juvenile boy from Ballito Bay, who lived ~2,000 years ago, demonstrates that southern African Stone Age hunter-gatherers were not impacted by recent admixture; however, we estimate that all modern-day Khoekhoe and San groups have been influenced by 9-22% genetic admixture from East African/Eurasian pastoralist groups arriving >1,000 years ago, including the Ju|'hoansi San, previously thought to have very low levels of admixture. Using traditional and new approaches, we estimate the population divergence time between the Ballito Bay boy and other groups to beyond 260,000 years ago. These estimates dramatically increases the deepest divergence amongst modern humans, coincide with the onset of the Middle Stone Age in sub-Saharan Africa, and coincide with anatomical developments of archaic humans into modern humans as represented in the local fossil record. Cumulatively, cross-disciplinary records increasingly point to southern Africa as a potential (not necessarily exclusive) 'hot spot' for the evolution of our species.

58: Evolution of Yin and Yang isoforms of a chromatin remodeling subunit results in the creation of two genes
more details view paper

Posted to bioRxiv 24 Apr 2019

Evolution of Yin and Yang isoforms of a chromatin remodeling subunit results in the creation of two genes
5 tweets evolutionary biology

Wen Xu, Lijiang Long, Yuehui Zhao, Lewis Stevens, Ronald E. Ellis, Patrick T McGrath

Genes can encode multiple isoforms, broadening their functions and providing a molecular substrate to evolve phenotypic diversity. Evolution of isoform function is a potential route to adapt to new environments. Here we show that de novo, beneficial alleles in the nurf-1 gene fixed in two laboratory strains of C. elegans after isolation from the wild in 1951, before methods of cryopreservation were developed. nurf-1 encodes an ortholog of BPTF, a large (>300kD) multidomain subunit of the NURF chromatin remodeling complex. Using CRISPR-Cas9 genome editing and transgenic rescue, we demonstrate that in C. elegans, nurf-1 has split into two, largely non-overlapping isoforms (NURF-1.B and NURF-1.D, which we call Yin and Yang) that share only two of 26 exons. Both isoforms are essential for normal gametogenesis but have opposite effects on male/female gamete differentiation. Reproduction in hermaphrodites, which involves production of both sperm and oocytes, requires a balance of these opposing Yin and Yang isoforms. Transgenic rescue and genetic position of the fixed mutations suggest that different isoforms are modified in each laboratory strain. In a related clade of Caenorhabditis nematodes, the shared exons have duplicated, resulting in the split of the Yin and Yang isoforms into separate genes, each containing approximately 200 amino acids of duplicated sequence that has undergone accelerated protein evolution following the duplication. Associated with this duplication event is the loss of two additional nurf-1 transcripts, including the long-form transcript and a newly identified, highly expressed transcript encoded by the duplicated exons. We propose these lost transcripts are non-functional biproducts necessary to transcribe the Yin and Yang transcripts in the same cells. Our work suggests that evolution of nurf-1 isoforms in nematodes creates adaptive conflict that can be resolved by the creation of new, independent genes.

59: Enhancers facilitate the birth of de novo genes and their functional integration into regulatory networks
more details view paper

Posted to bioRxiv 23 Apr 2019

Enhancers facilitate the birth of de novo genes and their functional integration into regulatory networks
5 tweets evolutionary biology

Paco Majic, Joshua Payne

Regulatory networks control the spatiotemporal gene expression patterns that give rise to and define the individual cell types of multicellular organisms. In Eumetazoa, distal regulatory elements called enhancers play a key role in determining the structure of such networks, particularly the wiring diagram of "who regulates whom." Mutations that affect enhancer activity can therefore rewire regulatory networks, potentially causing changes in gene expression that may be adaptive. Here, we use single-cell transcriptomic and chromatin accessibility data from mouse to show that enhancers play an additional role in the evolution of regulatory networks: They facilitate network growth by creating transcriptionally active regions of open chromatin that are conducive to de novo gene evolution. Specifically, our comparative transcriptomic analysis with three other mammalian species shows that young, mouse-specific transcribed open reading frames are preferentially located near enhancers, whereas older open reading frames are not. Interactions with enhancers are then gained incrementally over macro-evolutionary timescales, helping integrate new genes into existing regulatory networks. Taken together, our results highlight a dual role of enhancers in expanding and rewiring gene regulatory networks.

60: Discovery Of UFO Proteins: Human-Virus Chimeric Proteins Generated During Influenza Virus Infection
more details view paper

Posted to bioRxiv 08 Apr 2019

Discovery Of UFO Proteins: Human-Virus Chimeric Proteins Generated During Influenza Virus Infection
5 tweets microbiology

Yixuan Ma, Matthew Angel, Guojun Wang, Jessica Sook Yuin Ho, Nan Zhao, Justine Noel, Natasha Moshkina, James Gibbs, Jiajie Wei, Brad Rosenberg, Jeffrey Johnson, Max Chang, Zuleyma Peralta, Nevan Krogan, Christopher Benner, Harm van Bakel, Marta Łuksza, Benjamin D. Greenbaum, Emily R. Miraldi, Adolfo Garcia-Sastre, Jonathan W. Yewdell, Ivan Marazzi

Influenza A virus (IAV) is a threat to mankind because it generates yearly epidemics and poorly predictable sporadic pandemics with catastrophic potential. IAV has a small RNA genome composed of 8 mini-chromosomes (segments) that constitute a 5'UTR followed by a coding region and a 3'UTR. Transcription of IAV RNA into mRNA depends on host mRNA, as the viral polymerase cleaves 5'm7G-capped nascent transcripts to use as primers to initiate viral mRNA synthesis. We hypothesized that captured host transcripts bearing AUG could drive the expression of upstream ORFs in the viral segments, a phenomenon that would depend on the translatability of the viral 5'UTRs. Here we report the existence of this mechanism, which generates host-virus chimeric proteins. We label these proteins as Upstream Flu ORFs (UFO). Depending on the frame, two types of host-virus UFO proteins are made: canonical viral proteins with human-derived N term extensions or novel uncharacterized proteins. Here we show that both types are made during IAV infection. Sequences that enable chimeric protein synthesis are conserved across IAV strains, indicating that selection allowed the expansion of the proteome diversity of IAV in infected cells to include multiple human-virus proteins.

Previous page 1 2 3 4 5 6 7 . . . 20 Next page

Sign up for the Rxivist weekly newsletter! (Click here for more details.)


News