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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 63,068 bioRxiv papers from 279,747 authors.

Most downloaded bioRxiv papers, since beginning of last month

61,421 results found. For more information, click each entry to expand.

41: Long non-coding RNA gene regulation and trait associations across human tissues
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Posted to bioRxiv 04 Oct 2019

Long non-coding RNA gene regulation and trait associations across human tissues
1,109 downloads genetics

Olivia M. de Goede, Nicole M. Ferraro, Daniel C. Nachun, Abhiram Rao, François Aguet, Alvaro N Barbeira, Stephane E Castel, Sarah Kim-Hellmuth, YoSon Park, Alexandra J Scott, Benjamin J. Strober, GTEx Consortium, Christopher D Brown, Xiaoquan Wen, Ira M Hall, Alexis Battle, Tuuli Lappalainen, Hae Kyung Im, Kristin G Ardlie, Thomas Quertermous, Karla Kirkegaard, Stephen B. Montgomery

Long non-coding RNA (lncRNA) genes are known to have diverse impacts on gene regulation. However, it is still a major challenge to distinguish functional lncRNAs from those that are byproducts of surrounding transcriptional activity. To systematically identify hallmarks of biological function, we used the GTEx v8 data to profile the expression, regulation, network relationships and trait associations of lncRNA genes across 49 tissues encompassing 87 distinct traits. In addition to revealing widespread differences in regulatory patterns between lncRNA and protein-coding genes, we identified novel disease-associated lncRNAs, such as C6orf3 for psoriasis and LINC01475/RP11-129J12.1 for ulcerative colitis. This work provides a comprehensive resource to interrogate lncRNA genes of interest and annotate cell type and human trait relevance.

42: How neurons move during action potentials
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Posted to bioRxiv 11 Sep 2019

How neurons move during action potentials
1,082 downloads neuroscience

Tong Ling, Kevin C. Boyle, Valentina Zuckerman, Thomas Flores, Charu Ramakrishnan, Karl Deisseroth, Daniel Palanker

Neurons undergo nanometer-scale deformations during action potentials, and the underlying mechanism has been actively debated for decades. Previous observations were limited to a single spot or the cell boundary, while movement across the entire neuron during the action potential remained unclear. We report full-field imaging of cellular deformations accompanying the action potential in mammalian neuron somas (-1.8nm~1.3nm) and neurites (-0.7nm~0.9nm), using fast quantitative phase imaging with a temporal resolution of 0.1ms and an optical pathlength sensitivity of <4pm per pixel. Spike-triggered average, synchronized to electrical recording, demonstrates that the time course of the optical phase changes matches the dynamics of the electrical signal, with the optical signal revealing the intracellular potential rather than its time derivative detected via extracellular electrodes. Using 3D cellular morphology extracted via confocal microscopy, we demonstrate that the voltage-dependent changes in the membrane tension induced by ionic repulsion can explain the magnitude, time course and spatial features of the phase imaging. Our full-field observations of the spike-induced deformations in mammalian neurons opens the door to non-invasive label-free imaging of neural signaling.

43: Single-cell-resolution transcriptome map of human, chimpanzee, bonobo, and macaque brains
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Posted to bioRxiv 10 Sep 2019

Single-cell-resolution transcriptome map of human, chimpanzee, bonobo, and macaque brains
1,077 downloads evolutionary biology

Ekaterina Khrameeva, Ilia Kurochkin, Dingding Han, Patricia Guijarro, Sabina Kanton, Malgorzata Santel, Zhengzong Qian, Shen Rong, Pavel Mazin, Matvei Bulat, Olga Efimova, Anna Tkachev, Song Guo, Chet Sherwood, Gray Camp, Svante Paabo, Barbara Treutlein, Philipp Khaitovich

Identification of gene expression traits unique to the human brain sheds light on the mechanisms of human cognition. Here we searched for gene expression traits separating humans from other primates by analyzing 88,047 cell nuclei and 422 tissue samples representing 33 brain regions of humans, chimpanzees, bonobos, and macaques. We show that gene expression evolves rapidly within cell types, with more than two-thirds of cell type-specific differences not detected using conventional RNA sequencing of tissue samples. Neurons tend to evolve faster in all hominids, but non-neuronal cell types, such as astrocytes and oligodendrocyte progenitors, show more differences on the human lineage, including alterations of spatial distribution across neocortical layers.

44: A unified sequence catalogue of over 280,000 genomes obtained from the human gut microbiome
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Posted to bioRxiv 19 Sep 2019

A unified sequence catalogue of over 280,000 genomes obtained from the human gut microbiome
1,074 downloads microbiology

Alexandre Almeida, Stephen Nayfach, Miguel Boland, Francesco Strozzi, Martin Beracochea, Zhou Jason Shi, Katherine S Pollard, Donovan H Parks, Philip Hugenholtz, Nicola Segata, Nikos Kyrpides, Robert D. Finn

Comprehensive reference data is essential for accurate taxonomic and functional characterization of the human gut microbiome. Here we present the Unified Human Gastrointestinal Genome (UHGG) collection, a resource combining 286,997 genomes representing 4,644 prokaryotic species from the human gut. These genomes contain over 625 million protein sequences used to generate the Unified Human Gastrointestinal Protein (UHGP) catalogue, a collection that more than doubles the number of gut protein clusters over the Integrated Gene Catalogue. We find that a large portion of the human gut microbiome remains to be fully explored, with over 70% of the UHGG species lacking cultured representatives, and 40% of the UHGP missing meaningful functional annotations. Intra-species genomic variation analyses revealed a large reservoir of accessory genes and single-nucleotide variants, many of which were specific to individual human populations. These freely available genomic resources should greatly facilitate investigations into the human gut microbiome.

45: Dendritic calcium signals in rhesus macaque motor cortex drive an optical brain-computer interface
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Posted to bioRxiv 24 Sep 2019

Dendritic calcium signals in rhesus macaque motor cortex drive an optical brain-computer interface
1,067 downloads neuroscience

Eric M. Trautmann, Daniel J. O’Shea, Xulu Sun, James H Marshel, Ailey Crow, Brian Hsueh, Sam Vesuna, Lucas Cofer, Gergő Bohner, Will Allen, Isaac Kauvar, Sean Quirin, Matthew MacDougall, Yuzhi Chen, Matthew P. Whitmire, Charu Ramakrishnan, Maneesh Sahani, Eyal Seidemann, Stephen I Ryu, Karl Deisseroth, Krishna V Shenoy

Calcium imaging has rapidly developed into a powerful tool for recording from large populations of neurons in vivo . Imaging in rhesus macaque motor cortex can enable the discovery of new principles of motor cortical function and can inform the design of next generation brain-computer interfaces (BCIs). Surface two-photon (2P) imaging, however, cannot presently access somatic calcium signals of neurons from all layers of macaque motor cortex due to photon scattering. Here, we demonstrate an implant and imaging system capable of chronic, motion-stabilized two-photon (2P) imaging of calcium signals from in macaques engaged in a motor task. By imaging apical dendrites, some of which originated from deep layer 5 neurons, as as well as superficial cell bodies, we achieved optical access to large populations of deep and superficial cortical neurons across dorsal premotor (PMd) and gyral primary motor (M1) cortices. Dendritic signals from individual neurons displayed tuning for different directions of arm movement, which was stable across many weeks. Combining several technical advances, we developed an optical BCI (oBCI) driven by these dendritic signals and successfully decoded movement direction online. By fusing 2P functional imaging with CLARITY volumetric imaging, we verify that an imaged dendrite, which contributed to oBCI decoding, originated from a putative Betz cell in motor cortical layer 5. This approach establishes new opportunities for studying motor control and designing BCIs.

46: An inducible genome editing system for plants
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Posted to bioRxiv 23 Sep 2019

An inducible genome editing system for plants
1,063 downloads plant biology

Xin Wang, Lingling Ye, Robertas Ursache, Ari Pekka Mahonen

Conditional manipulation of gene expression is a key approach to investigating the primary function of a gene in a biological process. While conditional and cell-type specific overexpression systems exist for plants, there are currently no systems available to disable a gene completely and conditionally. Here, we present a novel tool with which target genes can be efficiently conditionally knocked out at any developmental stage. The target gene is manipulated using the CRISPR-Cas9 genome editing technology, and conditionality is achieved with the well-established estrogen-inducible XVE system. Target genes can also be knocked-out in a cell-type specific manner. Our tool is easy to construct and will be particularly useful for studying genes which have null-alleles that are non-viable or show strong developmental defects.

47: A tutorial on Gaussian process regression: Modelling, exploring, and exploiting functions
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Posted to bioRxiv 19 Dec 2016

A tutorial on Gaussian process regression: Modelling, exploring, and exploiting functions
1,019 downloads animal behavior and cognition

Eric Schulz, Maarten Speekenbrink, Andreas Krause

This tutorial introduces the reader to Gaussian process regression as an expressive tool to model, actively explore and exploit unknown functions. Gaussian process regression is a powerful, non-parametric Bayesian approach towards regression problems that can be utilized in exploration and exploitation scenarios. This tutorial aims to provide an accessible introduction to these techniques. We will introduce Gaussian processes which generate distributions over functions used for Bayesian non-parametric regression, and demonstrate their use in applications and didactic examples including simple regression problems, a demonstration of kernel-encoded prior assumptions and compositions, a pure exploration scenario within an optimal design framework, and a bandit-like exploration-exploitation scenario where the goal is to recommend movies. Beyond that, we describe a situation modelling risk-averse exploration in which an additional constraint (not to sample below a certain threshold) needs to be accounted for. Lastly, we summarize recent psychological experiments utilizing Gaussian processes. Software and literature pointers are also provided.

48: Single-cell RNA-sequencing reveals profibrotic roles of distinct epithelial and mesenchymal lineages in pulmonary fibrosis
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Posted to bioRxiv 06 Sep 2019

Single-cell RNA-sequencing reveals profibrotic roles of distinct epithelial and mesenchymal lineages in pulmonary fibrosis
1,016 downloads genomics

Arun C Habermann, Austin J Gutierrez, Linh T Bui, Stephanie L Yahn, Nichelle I Winters, Carla L Calvi, Lance M Peter, Mei-I Chung, Chase J Taylor, Christopher Jetter, Latha Raju, Jamie Roberson, Guixiao Ding, Lori Wood, Jennifer MS Sucre, Bradley W Richmond, Ana P Serezani, Wyatt J McDonnell, Simon B Mallal, Matthew J Bacchetta, James E Loyd, Ciara M Shaver, Lorraine B. Ware, Ross Bremner, Rajat Walia, Timothy S Blackwell, Nicholas E Banovich, Jonathan A Kropski

Pulmonary fibrosis is a form of chronic lung disease characterized by pathologic epithelial remodeling and accumulation of extracellular matrix. In order to comprehensively define the cell types, mechanisms and mediators driving fibrotic remodeling in lungs with pulmonary fibrosis, we performed single-cell RNA-sequencing of single-cell suspensions from 10 non-fibrotic control and 20 PF lungs. Analysis of 114,396 cells identified 31 distinct cell types. We report a remarkable shift in epithelial cell phenotypes occurs in the peripheral lung in PF, and identify several previously unrecognized epithelial cell phenotypes including a KRT5-/KRT17+, pathologic ECM-producing epithelial cell population that was highly enriched in PF lungs. Multiple fibroblast subtypes were observed to contribute to ECM expansion in a spatially-discrete manner. Together these data provide high-resolution insights into the complexity and plasticity of the distal lung epithelium in human disease, and indicate a diversity of epithelial and mesenchymal cells contribute to pathologic lung fibrosis.

49: Single molecule localization microscopy with autonomous feedback loops for ultrahigh precision
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Posted to bioRxiv 05 Dec 2018

Single molecule localization microscopy with autonomous feedback loops for ultrahigh precision
1,014 downloads biophysics

Simao Coelho, Jongho Baek, Matthew S Graus, James M Halstead, Philip R Nicovich, Kristen Feher, Hetvi Gandhi, Katharina Gaus

Single-molecule localization microscopy (SMLM) promises to provide truly molecular scale images of biological specimens. However, mechanical instabilities in the instrument, readout errors and sample drift constitute significant challenges and severely limit both the useable data acquisition length and the localization accuracy of single molecule emitters. Here, we developed an actively stabilized total internal fluorescence (TIRF) microscope that performs 3D real-time drift corrections and achieves a stability of ≤1 nm. Self-alignment of the emission light path and corrections of readout errors of the camera automate channel alignment and ensure localization precisions of 1-4 nm in DNA origami structures and cells for different labels. We used Feedback SMLM to measure the separation distance of signaling receptors and phosphatases in T cells. Thus, an improved SMLM enables direct distance measurements between molecules in intact cells on the scale between 1-20 nm, potentially replacing Forster resonance energy transfer (FRET) to quantify molecular interactions. In summary, by overcoming the major bottlenecks in SMLM imaging, it is possible to generate molecular images with nanometer accuracy and conduct distance measurements on the biological relevant length scales.

50: Template plasmid integration in germline genome-edited cattle.
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Posted to bioRxiv 28 Jul 2019

Template plasmid integration in germline genome-edited cattle.
1,012 downloads genomics

Alexis Norris, Stella S. Lee, Kevin J. Greenlees, Daniel A. Tadesse, Mayumi F Miller, Heather Lombardi

We analyzed publicly available whole genome sequencing data from cattle which were germline genome-edited to introduce polledness. Our analysis discovered the unintended heterozygous integration of the plasmid and a second copy of the repair template sequence, at the target site. Our finding underscores the importance of employing screening methods suited to reliably detect the unintended integration of plasmids and multiple template copies.

51: Cardelino: Integrating whole exomes and single-cell transcriptomes to reveal phenotypic impact of somatic variants
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Posted to bioRxiv 10 Sep 2018

Cardelino: Integrating whole exomes and single-cell transcriptomes to reveal phenotypic impact of somatic variants
1,009 downloads genomics

Davis McCarthy, Raghd Rostom, Yuanhua Huang, Daniel J Kunz, Petr Danecek, Marc Jan Bonder, Tzachi Hagai, HipSci Consortium, Wenyi Wang, Daniel J Gaffney, Benjamin D Simons, Oliver Stegle, Sarah A Teichmann

Decoding the clonal substructures of somatic tissues sheds light on cell growth, development and differentiation in health, ageing and disease. DNA-sequencing, either using bulk or using single-cell assays, has enabled the reconstruction of clonal trees from frequency and co-occurrence patterns of somatic variants. However, approaches to systematically characterize phenotypic and functional variations between individual clones are not established. Here we present cardelino (https://github.com/PMBio/cardelino), a computational method for inferring the clone of origin of individual cells that have been assayed using single-cell RNA-seq (scRNA-seq). After validating our model using simulations, we apply cardelino to matched scRNA-seq and exome sequencing data from 32 human dermal fibroblast lines, identifying hundreds of differentially expressed genes between cells from different somatic clones. These genes are frequently enriched for cell cycle and proliferation pathways, indicating a key role for cell division genes in non-neutral somatic evolution.

52: Improved metagenomic analysis with Kraken 2
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Posted to bioRxiv 07 Sep 2019

Improved metagenomic analysis with Kraken 2
1,002 downloads bioinformatics

Derrick E Wood, Jennifer Lu, Benjamin Langmead

Although Kraken's k-mer-based approach provides fast taxonomic classification of metagenomic sequence data, its large memory requirements can be limiting for some applications. Kraken 2 improves upon Kraken 1 by reducing memory usage by 85%, allowing greater amounts of reference genomic data to be used, while maintaining high accuracy and increasing speed five-fold. Kraken 2 also introduces a translated search mode, providing increased sensitivity in viral metagenomics analysis.

53: Daisyfield gene drive systems harness repeated genomic elements as a generational clock to limit spread
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Posted to bioRxiv 06 Feb 2017

Daisyfield gene drive systems harness repeated genomic elements as a generational clock to limit spread
1,000 downloads synthetic biology

John Min, Charleston Noble, Devora Najjar, Kevin M Esvelt

Methods of altering wild populations are most useful when inherently limited to local geographic areas. Here we describe a novel form of gene drive based on the introduction of multiple copies of an engineered 'daisy' sequence into repeated elements of the genome. Each introduced copy encodes guide RNAs that target one or more engineered loci carrying the CRISPR nuclease gene and the desired traits. When organisms encoding a drive system are released into the environment, each generation of mating with wild-type organisms will reduce the average number of the guide RNA elements per 'daisyfield' organism by half, serving as a generational clock. The loci encoding the nuclease and payload will exhibit drive only as long as a single copy remains, placing an inherent limit on the extent of spread.

54: Integrated Proteogenomic Deep Sequencing and Analytics Accurately Identify Non-Canonical Peptides in Tumor Immunopeptidomes
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Posted to bioRxiv 06 Sep 2019

Integrated Proteogenomic Deep Sequencing and Analytics Accurately Identify Non-Canonical Peptides in Tumor Immunopeptidomes
987 downloads cancer biology

Chloe Chong, Markus Muller, HuiSong Pak, Dermot Harnett, Florian Huber, Delphine Grun, Marion Leleu, Aymeric Auger, Marion Arnaud, Brian J Stevenson, Justine Michaux, Ilija Bilic, Antje Hirsekorn, Lorenzo Calviello, Laia Simo-Riudalbas, Evarist Planet, Jan Lubinski, Marta Bryskiewicz, Maciej Wiznerowicz, Ioannis Xenarios, Lin Zhang, Didier Trono, Alexandre Harari, Uwe Ohler, George Coukos, Michal Bassani-Sternberg

Efforts to precisely identify tumor human leukocyte antigen (HLA) bound peptides capable of mediating T cell-based tumor rejection still face important challenges. Recent studies suggest that non-canonical tumor-specific HLA peptides that derive from annotated non-coding regions could elicit anti-tumor immune responses. However, sensitive and accurate mass-spectrometry (MS)-based proteogenomics approaches are required to robustly identify these non-canonical peptides. We present an MS-based analytical approach that characterizes the non-canonical tumor HLA peptide repertoire, by incorporating whole exome sequencing, bulk and single cell transcriptomics, ribosome profiling, and a combination of two MS/MS search tools. This approach results in the accurate identification of hundreds of shared and tumor-specific non-canonical HLA peptides and of an immunogenic peptide from a downstream reading frame in the melanoma stem cell marker gene ABCB5. It holds great promise for the discovery of novel cancer antigens for cancer immunotherapy.

55: Cell type-specific enhancer-promoter connectivity maps in the human brain and disease risk association
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Posted to bioRxiv 22 Sep 2019

Cell type-specific enhancer-promoter connectivity maps in the human brain and disease risk association
985 downloads neuroscience

Alexi Nott, Inge R Holtman, Nicole G Coufal, Johannes C.M. Schlachetzki, Miao Yu, Rong Hu, Claudia Z Han, Monique Pena, Jiayang Xiao, Yin Wu, Zahara Keuelen, Martina P. Pasillas, Carolyn O'Connor, Simon T. Schafer, Zeyang Shen, Robert A Rissman, James B. Brewer, David Gosselin, David D. Gonda, Michael L. Levy, Michael G. Rosenfeld, Graham P McVicker, Fred H. Gage, Bing Ren, Christopher K Glass

Unique cell type-specific patterns of activated enhancers can be leveraged to interpret non-coding genetic variation associated with complex traits and diseases such as neurological and psychiatric disorders. Here, we have defined active promoters and enhancers for major cell types of the human brain. Whereas psychiatric disorders were primarily associated with regulatory regions in neurons, idiopathic Alzheimer's disease (AD) variants were largely confined to microglia enhancers. Interactome maps connecting GWAS variants in cell type-specific enhancers to gene promoters revealed an extended microglia gene network in AD. Deletion of a microglia-specific enhancer harboring AD-risk variants ablated BIN1 expression in microglia but not in neurons or astrocytes. These findings revise and expand the genes likely to be influenced by non-coding variants in AD and suggest the probable brain cell types in which they function.

56: HIV-1 Gag specifically restricts PI(4,5)P2 and cholesterol mobility in living cells creating a nanodomain platform for virus assembly.
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Posted to bioRxiv 21 Feb 2019

HIV-1 Gag specifically restricts PI(4,5)P2 and cholesterol mobility in living cells creating a nanodomain platform for virus assembly.
975 downloads biophysics

Cyril Favard, Jakub Chojnacki, Peggy Merida, Naresh Yandrapalli, Johnson Mak, Christian Eggeling, Delphine Muriaux

HIV-1 Gag protein self-assembles at the plasma membrane of infected cells for viral particle formation. Gag targets lipids, mainly the phosphatidylinositol (4,5) bisphosphate, at the inner leaflet of this membrane. Here, we address the question whether Gag is able to trap specifically PI(4,5)P2 or other lipids during HIV-1 assembly in the host CD4+ T lymphocytes. Lipid dynamics within and away from HIV-1 assembly sites was determined using super-resolution STED microscopy coupled with scanning Fluorescence Correlation Spectroscopy in living T cells. Analysis of HIV-1 infected cells revealed that, upon assembly, HIV-1 is able to specifically trap PI(4,5)P2, and cholesterol, but not phosphatidylethanolamine or sphingomyelin. Furthermore, our data show that Gag is the main driving force to restrict PI(4,5)P2 and cholesterol mobility at the cell plasma membrane. This is first direct evidence showing that HIV-1 creates its own specific lipid environment by selectively recruiting PI(4,5)P2 and cholesterol, as a membrane nano-platform for virus assembly.

57: Distinct RhoGEFs activate apical and junctional actomyosin contractility under control of G proteins during epithelial morphogenesis
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Posted to bioRxiv 04 Mar 2019

Distinct RhoGEFs activate apical and junctional actomyosin contractility under control of G proteins during epithelial morphogenesis
972 downloads developmental biology

Alain Garcia De Las Bayonas, Jean-Marc Philippe, Annemarie C. Lellouch, Thomas Lecuit

Small RhoGTPases and Myosin-II direct cell shape changes and movements during tissue morphogenesis. Their activities are tightly regulated in space and time to specify the desired pattern of contractility that supports tissue morphogenesis. This is expected to stem from polarized surface stimuli and from polarized signaling processing inside cells. We examined this general problem in the context of cell intercalation that drives extension of the Drosophila ectoderm. In the ectoderm, G protein coupled receptors (GPCRs) and their downstream heterotrimeric G proteins (Gα and Gβγ) activate Rho1 both medial-apically, where it exhibits pulsed dynamics, and at junctions, where its activity is planar polarized (Kerridge et al., 2016; Munjal et al., 2015). However, the mechanisms responsible for polarizing Rho1 activity are unclear. In particular, it is unknown how Rho1 activity is controlled at junctions. We report a division of labor in the mechanisms of Rho1 activation in that distinct guanine exchange factors (GEFs), that serve as activators of Rho1, operate in these distinct cellular compartments. RhoGEF2 acts uniquely to activate medial-apical Rho1. Although RhoGEF2 is recruited both medial-apically and at junctions by Gα12/13-GTP, also called Concertina (Cta) in Drosophila, its activity is restricted to the medial-apical compartment. Furthermore, we characterize a novel RhoGEF, p114RhoGEF/Wireless (Wrl), and report its requirement for cell intercalation in the extending ectoderm. p114RhoGEF/Wireless activates Rho1 specifically at junctions. Strikingly it is restricted to adherens junctions and is under Gβ13F/Gγ1 control. Gβ13F/Gγ1 activates junctional Rho1 and exerts quantitative control over planar polarization of Rho1. In particular, overexpression of Gβ13F/Gγ1 leads to hyper planar polarization of Rho1 and MyoII. Finally, we found that p114RhoGEF/Wireless is absent in the mesoderm, arguing for a tissue-specific control over junctional Rho1 activity. These results shed light on the mechanisms of polarization of Rho1 activity in different cellular compartments and reveal that distinct GEFs are sensitive tuning parameters of cell contractility in remodeling epithelia.

58: Microtubules promote intercellular contractile force transmission during tissue folding
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Posted to bioRxiv 04 Feb 2019

Microtubules promote intercellular contractile force transmission during tissue folding
964 downloads developmental biology

Clint Shijun Ko, Vardges Tserunyan, Adam C Martin

During development, forces transmitted between cells are critical for sculpting epithelial tissues. Actomyosin contractility in the middle of the cell apex (medioapical) can change cell shape (e.g., apical constriction), but can also result in force transmission between cells via attachments to adherens junctions. How actomyosin networks maintain attachments to adherens junctions under tension is poorly understood. Here, we discovered that microtubules promote actomyosin intercellular attachments in epithelia during Drosophila mesoderm invagination. First, we used live imaging to show a novel arrangement of the microtubule cytoskeleton during apical constriction: medioapical Patronin (CAMSAP) foci formed by actomyosin contraction organized an apical non-centrosomal microtubule network. Microtubules were required for mesoderm invagination but were not necessary for initiating apical contractility or adherens junction assembly. Instead, microtubules promoted connections between medioapical actomyosin and adherens junctions. These results delineate a role for coordination between actin and microtubule cytoskeletal systems in intercellular force transmission during tissue morphogenesis.

59: The Spatio-Temporal Control of Zygotic Genome Activation
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Posted to bioRxiv 06 Dec 2018

The Spatio-Temporal Control of Zygotic Genome Activation
963 downloads developmental biology

George E Gentsch, Nick D L Owens, James C Smith

One of the earliest and most significant events in embryonic development is zygotic genome activation (ZGA). In several species, bulk transcription begins at the mid-blastula transition (MBT) when, after a certain number of cleavages, the embryo attains a particular nuclear-to-cytoplasmic (N/C) ratio, maternal repressors become sufficiently diluted, and the cell cycle slows down. Here we resolve the frog ZGA in time and space by profiling RNA polymerase II (RNAPII) engagement and its transcriptional readout. We detect a gradual increase in both the quantity and the length of RNAPII elongation before the MBT, revealing that >1,000 zygotic genes disregard the N/C timer for their activation, and that the sizes of newly transcribed genes are not necessarily constrained by cell cycle duration. We also find that Wnt, Nodal and BMP signaling together generate most of the spatio-temporal dynamics of regional ZGA, directing the formation of orthogonal body axes and proportionate germ layers.

60: Distinguishing between parallel and serial processing in visual attention from neurobiological data
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Posted to bioRxiv 02 Aug 2018

Distinguishing between parallel and serial processing in visual attention from neurobiological data
955 downloads neuroscience

Kang Li, Mikiko Kadohisa, Makoto Kusunoki, John Duncan, Claus Bundesen, Susanne Ditlevsen

Serial and parallel processing in visual search have been long debated in psychology but the processing mechanism remains an open issue. Serial processing allows only one object at a time to be processed, whereas parallel processing assumes that various objects are processed simultaneously. Here we present novel neural models for the two types of processing mechanisms based on analysis of simultaneously recorded spike trains using electrophysiological data from prefrontal cortex of rhesus monkeys while processing task-relevant visual displays. We combine mathematical models describing neuronal attention and point process models for spike trains. The same model can explain both serial and parallel processing by adopting different parameter regimes. We present statistical methods to distinguish between serial and parallel processing based on both maximum likelihood estimates and decoding analysis of the attention when two stimuli are presented simultaneously. Results show that both processing mechanisms are in play for the simultaneously recorded neurons, but neurons tend to follow parallel processing in the beginning after the onset of the stimulus pair, whereas they tend to serial processing later on. This could be explained by parallel processing being related to sensory bottom-up signals or feedforward processing, which typically occur in the beginning after stimulus onset, whereas top-down signals related to cognitive modulatory influences guiding attentional effects in recurrent feedback connections occur after a small delay, and is related to serial processing, where all processing capacities are being directed towards the attended object.

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