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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 55,243 bioRxiv papers from 254,840 authors.

Most downloaded bioRxiv papers, since beginning of last month

52,136 results found. For more information, click each entry to expand.

341: Garcinia cambogia extract removes calcium oxalate kidney stones in both genetic and non-genetic Drosophila models of nephrolithiasis
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Posted to bioRxiv 27 Nov 2018

Garcinia cambogia extract removes calcium oxalate kidney stones in both genetic and non-genetic Drosophila models of nephrolithiasis
326 downloads pharmacology and toxicology

Qiuxia Fan, Xiaoming Feng, Xizhen Hong, Siqiao Gong, Jianwei Tian, Fanfan Hou, Fujian Zhang

Kidney stone formers with family history have a high rate of stone recurrence after kidney stone removal surgery and there is no effective medication available for treatment. Here, we show that Garcinia cambogia extract (GCE) efficiently removes calcium oxalate kidney stones from Malpighian tubules in both genetic and non-genetic Drosophila models of nephrolithiasis, and hydroxycitrate -a major component of GCE, directly dissolves calcium oxalate stones in Drosophila Malpighian tubules ex vivo. Our study discovers a potential novel therapeutic strategy for the clinical treatment of nephrolithiasis and suggests that clinical-grade Garcinia cambogia extract could be used to treat patients with nephrolithiasis in the future.

342: Tracking of antibiotic resistance transfer and rapid plasmid evolution in a hospital setting by Nanopore sequencing
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Posted to bioRxiv 17 May 2019

Tracking of antibiotic resistance transfer and rapid plasmid evolution in a hospital setting by Nanopore sequencing
326 downloads genomics

Silke Peter, Mattia Bosio, Caspar Gross, Daniela Bezdan, Javier Gutierrez, Philipp Oberhettinger, Jan Liese, Wichard Vogel, Daniela Doerfel, Lennard Berger, Matthias Marschal, Matthias Willmann, Ivo Gut, Marta Gut, Ingo Autenrieth, Stephan Ossowski

Background: Infection of patients with multidrug-resistant (MDR) bacteria often leave very limited or no treatment options. The transfer of antimicrobial resistance genes (ARG) carrying plasmids between bacterial species by horizontal gene transfer represents an important mode of expansion of ARGs. Here, we evaluated the application of Nanopore sequencing technology in a hospital setting for monitoring the transfer and rapid evolution of antibiotic resistance plasmids within and across multiple species. Results: In 2009 we experienced an outbreak with an extensively multidrug resistant P. aeruginosa harboring the carbapenemase enzyme blaIMP-8, and in 2012 the first Citrobacter freundii and Citrobacter werkmanii harboring the same enzyme were detected. Using Nanopore and Illumina sequencing we conducted a comparative analysis of all blaIMP-8 bacteria isolated in our hospital over a 6-year period (n = 54). We developed the computational platforms pathoLogic and plasmIDent for Nanopore-based characterization of clinical isolates and monitoring of ARG transfer, comprising de-novo assembly of genomes and plasmids, polishing, QC, plasmid circularization, ARG annotation, comparative genome analysis of multiple isolates and visualization of results. Using plasmIDent we identified a 40 kb plasmid carrying blaIMP-8 in P. aeruginosa and C. freundii, verifying that plasmid transfer had occurred. Within C. freundii the plasmid underwent further evolution and plasmid fusion, resulting in a 164 kb mega-plasmid, which was transferred to C. werkmanii. Moreover, multiple rearrangements of the multidrug resistance gene cassette were detected in P. aeruginosa, including deletions and translocations of complete ARGs. Conclusion: Plasmid transfer, plasmid fusion and rearrangement of the multidrug resistance gene cassette mediated the rapid evolution of opportunistic pathogens in our hospital. We demonstrated the feasibility of tracking plasmid evolution dynamics and ARG transfer in clinical settings in a timely manner. The approach will allow for successful countermeasures to contain not only clonal, but also plasmid mediated outbreaks.

343: Real-time cryo-EM data pre-processing with Warp
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Posted to bioRxiv 14 Jun 2018

Real-time cryo-EM data pre-processing with Warp
325 downloads biophysics

Dimitry Tegunov, Patrick Cramer

The acquisition of cryo-electron microscopy (cryo-EM) data from biological specimens is currently largely uncoupled from subsequent data evaluation, correction and processing. Therefore, the acquisition strategy is difficult to optimize during data collection, often leading to suboptimal microscope usage and disappointing results. Here we provide Warp, a software for real-time evaluation, correction, and processing of cryo-EM data during their acquisition. Warp evaluates and monitors key parameters for each recorded micrograph or tomographic tilt series in real time. Warp also rapidly corrects micrographs for global and local motion, and estimates the local defocus with the use of novel algorithms. The software further includes a deep learning-based particle picking algorithm that rivals human accuracy to make the pre-processing pipeline truly automated. The output from Warp can be directly fed into established tools for particle classification and 3D image reconstruction. In a benchmarking study we show that Warp automatically processed a published cryo-EM data set for influenza virus hemagglutinin, leading to an improvement of the nominal resolution from 3.9 Å to 3.2 Å. Warp is easy to install, computationally inexpensive, and has an intuitive and streamlined user interface.

344: Single-cell profiling guided combinatorial immunotherapy for fast-evolving CDK4/6 inhibitor resistant HER2-positive breast cancer
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Posted to bioRxiv 14 Jun 2019

Single-cell profiling guided combinatorial immunotherapy for fast-evolving CDK4/6 inhibitor resistant HER2-positive breast cancer
324 downloads cancer biology

Qingfei Wang, Ian M Guldner, Samantha M Golomb, Longhua Sun, Jack Harris, Xin Lu, Siyuan Zhang

Development of acquired resistance to targeted cancer therapy is one of the most significant clinical challenges. Acquiring resistance under drug selection pressure is a result of evolutionary adaptation to a complex and dynamic tumor microenvironment (TME). New therapy regimens combining CDK4/6 inhibitor are under active investigation in clinical trials to treat HER2+ breast cancer patients. In parallel with clinical trial settings, in this study, we sought to prospectively model the tumor evolution in response to a targeted therapy regimen in vivo and identify a clinically actionable strategy to combat potential acquired resistance. Notably, despite a promising initial response, acquired resistance emerged rapidly to the anti-Her2/Neu antibody plus CDK4/6 inhibitor Palbociclib combination treatment. By leveraging high-throughput single-cell analyses of the evolving tumors over the course of treatments, we revealed a distinct immunosuppressive immature myeloid cell (IMC) population infiltrated in the resistant TME. Guided by single-cell transcriptome analysis, we demonstrated a combinatorial immunotherapy of IMC-targeting tyrosine kinase inhibitor cabozantinib and immune checkpoint blockades enhanced anti-tumor immunity, and overcame the resistance. Further, sequential combinatorial immunotherapy enabled a sustained control of the rapidly evolving CDK4/6 inhibitor-resistant tumors. Our study demonstrates a translational framework for treating rapidly evolving tumors through preclinical modeling and single-cell analyses. Our findings provide a rationale for an immediate clinical proposition of combinatorial immunotherapy for HER2+ breast cancer as a strategy to mitigate the emergence of resistance.

345: scVAE: Variational auto-encoders for single-cell gene expression data
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Posted to bioRxiv 16 May 2018

scVAE: Variational auto-encoders for single-cell gene expression data
323 downloads bioinformatics

Christopher Heje Grønbech, Maximillian Fornitz Vording, Pascal Nordgren Timshel, Casper Kaae Sønderby, Tune Hannes Pers, Ole Winther

Motivation: Models for analysing and making relevant biological inferences from massive amounts of complex single-cell transcriptomic data typically require several individual data- processing steps, each with their own set of hyperparameter choices. With deep generative models one can work directly with count data, make likelihood-based model comparison, learn a latent representation of the cells and capture more of the variability in different cell populations. Results: We propose a novel method based on variational auto-encoders (VAEs) for analysis of single-cell RNA sequencing (scRNA-seq) data. It avoids data preprocessing by using raw count data as input and can robustly estimate the expected gene expression levels and a latent representation for each cell. We tested several count likelihood functions and a variant of the VAE that has a priori clustering in the latent space. We show for several scRNA-seq data sets that our method outperforms recently proposed scRNA-seq methods in clustering cells and that the resulting clusters reflect cell types. Availability and implementation: Our method, called scVAE, is implemented in Python using the TensorFlow machine-learning library, and it is freely available at https://github. com/chgroenbech/scVAE.

346: Accurate estimation of cell composition in bulk expression through robust integration of single-cell information
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Posted to bioRxiv 15 Jun 2019

Accurate estimation of cell composition in bulk expression through robust integration of single-cell information
323 downloads bioinformatics

Brandon Jew, Marcus Alvarez, Elior Rahmani, Zong Miao, Arthur Ko, Jae Hoon Sul, Kirsi H Pietiläinen, Päivi Pajukanta, Eran Halperin

We present Bisque, a tool for estimating cell type proportions in bulk expression. Bisque implements a regression-based approach that utilizes single-cell RNA-seq (scRNA-seq) data to generate a reference expression profile and learn gene-specific bulk expression transformations to robustly decompose RNA-seq data. These transformations significantly improve decomposition performance compared to existing methods when there is significant technical variation in the generation of the reference profile and observed bulk expression. Importantly, compared to existing methods, our approach is extremely efficient, making it suitable for the analysis of large genomic datasets that are becoming ubiquitous. When applied to subcutaneous adipose and dorsolateral prefrontal cortex expression datasets with both bulk RNA-seq and single-nucleus RNA-seq (snRNA-seq) data, Bisque was able to replicate previously reported associations between cell type proportions and measured phenotypes across abundant and rare cell types. Bisque requires a single-cell reference dataset that reflects physiological cell type composition and can further leverage datasets that includes both bulk and single cell measurements over the same samples for improved accuracy. We further propose an additional mode of operation that merely requires a set of known marker genes. Bisque is available as an R package at: https://github.com/cozygene/bisque.

347: Developmental myelination is modified by microglial pruning
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Posted to bioRxiv 03 Jun 2019

Developmental myelination is modified by microglial pruning
323 downloads neuroscience

Alexandria N. Hughes, Bruce Appel

During development, oligodendrocytes contact and wrap neuronal axons with myelin. Similar to neurons and synapses, excess myelin sheaths are produced and selectively eliminated. However, unlike these other structures, almost nothing is known about myelin sheath elimination. Microglia, the resident immune cells of the CNS, refine the developing CNS by engulfing surplus neurons and synapses. To determine if microglia also prune myelin sheaths, we used zebrafish to visualize and manipulate interactions between microglia, oligodendrocytes, and neurons during development. We found that microglia closely associate with oligodendrocytes and specifically phagocytose myelin sheaths. Silencing neuronal activity with botulinum toxin (BoNT/B) increased myelin engulfment by microglia. Furthermore, oligodendrocytes maintained excessive myelin sheaths following microglial ablation. Our work reveals a neuronal activity-regulated role for microglia in regulating myelination by oligodendrocytes.

348: Direct RNA nanopore sequencing of full-length coronavirus genomes provides novel insights into structural variants and enables modification analysis
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Posted to bioRxiv 30 Nov 2018

Direct RNA nanopore sequencing of full-length coronavirus genomes provides novel insights into structural variants and enables modification analysis
322 downloads genomics

Adrian Viehweger, Sebastian Krautwurst, Kevin Lamkiewicz, Ramakanth Madhugiri, John Ziebuhr, Martin Hölzer, Manja Marz

Sequence analyses of RNA virus genomes remain challenging due to the exceptional genetic plasticity of these viruses. Because of high mutation and recombination rates, genome replication by viral RNA-dependent RNA polymerases leads to populations of closely related viruses that are generally referred to as quasispecies. Although standard (short-read) sequencing technologies allow to readily determine consensus sequences for these quasispecies, it is far more difficult to reconstruct large numbers of full-length haplotypes of (i) RNA virus genomes and (ii) subgenome-length (sg) RNAs comprised of noncontiguous genome regions that may be present in these virus populations. Here, we used a full-length, direct RNA sequencing (DRS) approach without any amplification step to characterize viral RNAs produced in cells infected with a human coronavirus representing one of the largest RNA virus genomes known to date. Using DRS, we were able to map the longest (~26 kb) contiguous read to the viral reference genome. By combining Illumina and nanopore sequencing, a highly accurate consensus sequence of the human coronavirus (HCoV) 229E genome (27.3 kb) was reconstructed. Furthermore, using long reads that did not require an assembly step, we were able to identify, in infected cells, diverse and novel HCoV-229E sg RNAs that remain to be characterized. Also, the DRS approach, which does not require reverse transcription and amplification of RNA, allowed us to detect methylation sites in viral RNAs. Our work paves the way for haplotype-based analyses of viral quasispecies by demonstrating the feasibility of intra-sample haplotype separation. We also show how supplementary short-read sequencing (Illumina) can be used to reduce the error rate of nanopore sequencing. Even though a number of technical challenges remain to be addressed to fully exploit the potential of the nanopore technology, our work illustrates that direct RNA sequencing may significantly advance genomic studies of complex virus populations, including predictions on long-range interactions in individual full-length viral RNA haplotypes.

349: Gastruloid development competence discriminates different states of pluripotency between naïve and primed
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Posted to bioRxiv 08 Jun 2019

Gastruloid development competence discriminates different states of pluripotency between naïve and primed
322 downloads developmental biology

Federica Cermola, Cristina D'Aniello, Rosarita Tatè, Dario De Cesare, Alfonso Martinez-Arias, Gabriella Minchiotti, Eduardo J Patriarca

Floating spheroidal aggregates (aggregomes) of mouse embryonic stem cells (mESCs) can develop into polarized/elongated organoids, namely gastruloids. Here we report a high-performing assay to measure gastruloids formation efficiency (GFE), i.e. the fraction of gastruloid-developing aggregomes. By exploiting this procedure, we provide morphological and molecular evidence that gastruloid development relies on Cripto. We also demonstrate that GFE decreases as pluripotency progresses from naive to primed state. Indeed, naive ESC-derived aggregomes efficiently elongate (GFE≥95%), while primed EpiSCs fail to aggregate and consequently to generate gastruloids (GFE=0%). Conversely, while early-primed EpiLCs properly aggregate, EpiLC-derived aggregomes are mostly abortive (GFE=0%). Unlike EpiLCs, L-Proline-treated ESCs (PiCs) generate productive aggregomes (GFE≥50%), which however begin to elongate earlier and generate smaller gastruloids that appear more differentiated. Like EpiLCs, PiCs are competent to differentiate into primordial germ cell-like cells (PGCLCs), suggesting that PiCs capture an EpiLC-like state with unique competence for both gastruloid formation and differentiation into PGCLCs. Thus we propose GFE assay as a simple and robust in vitro method to discriminate different phenotypic/functional states of the pluripotency continuum.

350: Electrophilic PROTACs that degrade nuclear proteins by engaging DCAF16
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Posted to bioRxiv 15 Oct 2018

Electrophilic PROTACs that degrade nuclear proteins by engaging DCAF16
322 downloads biochemistry

Xiaoyu Zhang, Vincent M Crowley, Thomas G Wucherpfennig, Melissa M Dix, Benjamin F Cravatt

Ligand-dependent protein degradation has emerged as a compelling strategy to pharmacologically control the protein content of cells. So far, only a limited number of E3 ligases have been found to support this process. Here, we use a chemical proteomic strategy to discover that DCAF16 - a poorly characterized substrate recognition component of CUL4-DDB1 E3 ubiquitin ligases - promotes nuclear-restricted protein degradation upon modification by cysteine-directed heterobifunctional electrophilic compounds.

351: Distinct Contribution of DNA Methylation and Histone Acetylation to the Genomic Occupancy of Transcription Factors
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Posted to bioRxiv 13 Jun 2019

Distinct Contribution of DNA Methylation and Histone Acetylation to the Genomic Occupancy of Transcription Factors
321 downloads molecular biology

Martin Cusack, Hamish W King, Paolo Spingardi, Benedikt Kessler, Robert J Klose, Skirmantas Kriaucionis

Epigenetic modifications on chromatin play important roles in regulating gene expression. While chromatin states are often governed by multi-layered structure, how individual pathways contribute to gene expression remains poorly understood. For example, DNA methylation is known to regulate transcription factor binding but also to recruit methyl-CpG binding proteins that affect chromatin structure through the activity of histone deacetylase complexes (HDACs). Both of these mechanisms can potentially affect gene expression, but the importance of each, and whether these activities are integrated to achieve appropriate gene regulation, remains largely unknown. To address this important question, we measured gene expression, chromatin accessibility, and transcription factor occupancy in wild-type or DNA methylation-deficient mouse embryonic stem cells following HDAC inhibition. Interestingly, we observe widespread increases in chromatin accessibility at repeat elements when HDACs are inhibited, and this is magnified when cells also lack DNA methylation. A subset of these elements have elevated binding of the YY1 and GABPA transcription factors and increased expression. The pronounced additive effect of HDAC inhibition in DNA methylation deficient cells demonstrate that DNA methylation and histone deacetylation act largely independently to suppress transcription factor binding and gene expression.

352: RamaNet: Computational De Novo Protein Design using a Long Short-Term Memory Generative Adversarial Neural Network
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Posted to bioRxiv 14 Jun 2019

RamaNet: Computational De Novo Protein Design using a Long Short-Term Memory Generative Adversarial Neural Network
321 downloads bioinformatics

Sari Sabban, Mikhail Markovsky

The ability to perform De novo protein design will allow researchers to expand the pool and variety of available proteins, by designing synthetic structures computationally they can make available more structures than are available in the Protein Data Bank, design structures that are not found in nature, or direct the design of proteins to acquire a specific desired structure. While some researchers attempt to design proteins from first physical and thermodynamic principals, we decided to attempt to perform de novo protein design statistically using machine learning by building a model that uses a long short-term memory generative adversarial neural network architecture. The LSTM based GAN model used the Φ and Ψ angles of each residue from an augmented dataset of only helical protein structures. Though the network's output structures were not perfect, they were idealised and evaluated post prediction where the bad structures were filtered out and the adequate structures kept. The results were successful in developing a logical, rigid, compact, helical protein backbone topology. This backbone topology was then used to computationally design side chains that should allow the final protein to fold to the designed structure.

353: Patterns of genetic differentiation and the footprints of historical migrations in the Iberian Peninsula
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Posted to bioRxiv 12 Mar 2018

Patterns of genetic differentiation and the footprints of historical migrations in the Iberian Peninsula
320 downloads genomics

Clare Bycroft, Ceres Fernández-Rozadilla, Clara Ruiz-Ponte, Iéns Quintela-García, Ángel Carracedo, Peter Donnelly, Simon Myers

Genetic differences within or between human populations (population structure) has been studied using a variety of approaches over many years. Recently there has been an increasing focus on studying genetic differentiation at fine geographic scales, such as within countries. Identifying such structure allows the study of recent population history, and identifies the potential for confounding in association studies, particularly when testing rare, often recently arisen variants. The Iberian Peninsula is linguistically diverse, has a complex demographic history, and is unique among European regions in having a centuries-long period of Muslim rule. Previous genetic studies of Spain have examined either a small fraction of the genome or only a few Spanish regions. Thus, the overall pattern of fine-scale population structure within Spain remains uncharacterised. Here we analyse genome-wide genotyping array data for 1,413 Spanish individuals sampled from all regions of Spain. We identify extensive fine-scale structure, down to unprecedented scales, smaller than 10 Km in some places. We observe a major axis of genetic differentiation that runs from east to west of the peninsula. In contrast, we observe remarkable genetic similarity in the north-south direction, and evidence of historical north-south population movement. Finally, without making particular prior assumptions about source populations, we show that modern Spanish people have regionally varying fractions of ancestry from a group most similar to modern north Moroccans. The north African ancestry results from an admixture event, which we date to 860 - 1120 CE, corresponding to the early half of Muslim rule. Our results indicate that it is possible to discern clear genetic impacts of the Muslim conquest and population movements associated with the subsequent Reconquista.

354: Germline maintenance through the multifaceted activities of GLH/Vasa in Caenorhabditis elegans P granules
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Posted to bioRxiv 06 Jun 2019

Germline maintenance through the multifaceted activities of GLH/Vasa in Caenorhabditis elegans P granules
320 downloads developmental biology

Elisabeth A Marnik, J Heath Fuqua, Catherine S Sharp, Jesse D Rochester, Emily L Xu, Sarah E Holbrook, Dustin L Updike

Vasa is a highly conserved member of the ATP-dependent DEAD box helicase family, a multipotency factor, and a critical component for the specification and maintenance of the germline. Its homologs have been shown to regulate translation, small RNA amplification, and serve as a molecular solvent for single-stranded RNA; however, the function of Vasa defining domains and what they interact with are unclear. To address this, 28 mutant alleles of the C. elegans Vasa homolog GLH-1 were generated in conserved motifs. Mutations in the flanking and helicase domains show that GLH-1 retains its association with P granules through its helicase activity and not through static interactions with other P-granule proteins. Changes outside of these domains retain GLH-1 in P granules but still compromise fertility, and removal of glycine-rich repeats progressively diminish P-granule wetting-like interactions at the nuclear periphery. A mutation that facilitates Vasa aggregation was previously leveraged in insects and mammals to identify the transient association of Vasa with piRNA amplifying Argonautes. This same mutation in GLH-1 also stimulates aggregation and association with Argonautes, suggesting that the transient amplifying complex is evolutionarily conserved even though the method of piRNA amplification in C. elegans is not. Mass spectrometry analysis of proteins that co-immunoprecipitate with wild type and mutant GLH-1 reveal an affinity for all three PCI (26S Proteasome Lid, COP9, eIF3) scaffolding complexes, which regulate protein turnover and translation, and a possible aversion for ribosomes and the 26S proteasome core. These results suggest that phase-separated P granules compartmentalize the cytoplasm to exclude large protein assemblies and emphasize the role of Vasa homologs in maintaining proteostasis.

355: CRISPR adenine and cytosine base editors with reduced RNA off-target activities
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Posted to bioRxiv 09 May 2019

CRISPR adenine and cytosine base editors with reduced RNA off-target activities
319 downloads molecular biology

Julian Grunewald, Ronghao Zhou, Sowmya Iyer, Caleb A Lareau, Sara P. Garcia, Martin J Aryee, J. Keith Joung

CRISPR-guided DNA base editors enable the efficient installation of targeted single-nucleotide changes. Cytosine or adenine base editors (CBEs or ABEs), which are fusions of cytidine or adenosine deaminases to CRISPR-Cas nickases, can efficiently induce DNA C-to-T or A-to-G alterations in DNA, respectively. We recently demonstrated that both the widely used CBE BE3 (harboring a rat APOBEC1 cytidine deaminase) and the optimized ABEmax editor can induce tens of thousands of guide RNA-independent, transcriptome-wide RNA base edits in human cells with high efficiencies. In addition, we showed the feasibility of creating SElective Curbing of Unwanted RNA Editing (SECURE)-BE3 variants that exhibit substantially reduced unwanted RNA editing activities while retaining robust and more precise on-target DNA editing. Here we describe structure-guided engineering of SECURE-ABE variants that not only possess reduced off-target RNA editing with comparable on-target DNA activities but are also the smallest Streptococcus pyogenes Cas9 (SpCas9) base editors described to date. In addition, we tested CBEs composed of cytidine deaminases other than APOBEC1 and found that human APOBEC3A (hA3A) cytidine deaminase CBE induces substantial transcriptome-wide RNA base edits with high efficiencies. By contrast, a previously described enhanced A3A (eA3A) cytidine deaminase CBE or a human activation-induced cytidine deaminase (hAID) CBE induce substantially reduced or near background levels of RNA edits. In sum, our work describes broadly useful SECURE-ABE and -CBE base editors and reinforces the importance of minimizing RNA editing activities of DNA base editors for research and therapeutic applications.

356: Assembly of a persistent apical actin network by the formin Frl/Fmnl tunes epithelial cell deformability
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Posted to bioRxiv 23 Jun 2019

Assembly of a persistent apical actin network by the formin Frl/Fmnl tunes epithelial cell deformability
319 downloads developmental biology

Benoit Dehapiot, Raphaël Clément, Gabriella Gazsó-Gerhát, Jean-Marc Philippe, Thomas Lecuit

Tissue remodeling during embryogenesis is driven by the apical contractility of the epithelial cell cortex. This behavior arises notably from Rho1/Rok induced transient accumulation of non-muscle myosin II (MyoII pulses) pulling on actin filaments (F-Actin) of the medio-apical cortex. While recent studies begin to highlight the mechanisms governing the emergence of Rho1/Rok/MyoII pulsatility in different organisms, little is known about how the F-Actin organization influences this process. Focusing on Drosophila ectodermal cells during germband extension and amnioserosa cells during dorsal closure, we show that the medio-apical actomyosin cortex consists of two entangled F-Actin subpopulations. One exhibits pulsatile dynamics of actin polymerization in a Rho1 dependent manner. The other forms a persistent and homogeneous network independent of Rho1. We identify the Frl/Fmnl formin as a critical nucleator of the persistent network since modulating its level, in mutants or by overexpression, decreases or increases the network density. Absence of this network yields sparse connectivity affecting the homogeneous force transmission to the cell boundaries. This reduces the propagation range of contractile forces and results in tissue scale morphogenetic defects. Our work sheds new lights on how the F-Actin cortex offers multiple levels of regulation to affect epithelial cells dynamics.

357: Pre-existent adult sox10+ cardiomyocytes contribute to myocardial regeneration in the zebrafish
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Posted to bioRxiv 07 Jun 2019

Pre-existent adult sox10+ cardiomyocytes contribute to myocardial regeneration in the zebrafish
319 downloads developmental biology

Marcos Sande-Melón, Inês J Marques, María Galardi-Castilla, Xavier Langa, María Pérez-López, Marius Botos, Gabriela Martínez-Guzmán, David Miguel Ferreira-Francisco, Dinko Pavlinic, Vladimir Benes, Remy Bruggmann, Nadia Mercader

During heart regeneration in the zebrafish, fibrotic tissue is replaced by newly formed cardiomyocytes derived from pre-existing ones. It is unclear whether the heart is comprised of several cardiomyocyte populations bearing different capacity to replace lost myocardium. Here, using sox10 genetic fate mapping, we identified a subset of pre-existent cardiomyocytes in the adult zebrafish heart with a distinct gene expression profile that expanded massively after cryoinjury. Genetic ablation of sox10+ cardiomyocytes severely impaired cardiac regeneration revealing that they play a crucial role for heart regeneration.

358: c-Jun Overexpressing CAR-T Cells are Exhaustion-Resistant and Mediate Enhanced Antitumor Activity
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Posted to bioRxiv 29 May 2019

c-Jun Overexpressing CAR-T Cells are Exhaustion-Resistant and Mediate Enhanced Antitumor Activity
318 downloads immunology

Rachel Christina Lynn, Evan W Weber, David Gennert, Elena Sotillo, Peng Xu, Zinaida Good, Hima Anbunathan, Robert Jones, Victor Tieu, Jeffrey Granja, Charles DeBourcy, Robbie Majzner, Ansuman Satpathy, Stephen R. Quake, Howard Chang, Crystal L Mackall

CAR T cells mediate antitumor effects in a small subset of cancer patients, but dysfunction due to T cell exhaustion is an important barrier to progress. To investigate the biology of exhaustion in human T cells expressing CAR receptors, we used a model system employing a tonically signaling CAR, which induces hallmarks of exhaustion described in other settings. Exhaustion was associated with a profound defect in IL-2 production alongside increased chromatin accessibility of AP-1 transcription factor motifs, and overexpression of bZIP and IRF transcription factors that have been implicated in driving exhaustion. Here we demonstrate that engineering CAR T cells to overexpress c-Jun, a canonical AP-1 factor, enhanced expansion potential, increased functional capacity, diminished terminal differentiation and improved antitumor potency in five different in vivo tumor models. We conclude that a functional deficiency in c-Jun mediates dysfunction in exhausted human T cells and that engineering CAR T cells to overexpress c-Jun renders them exhaustion-resistant, thereby addressing a major barrier to progress for this emerging class of therapeutics.

359: Minor allele frequency thresholds strongly affect population structure inference with genomic datasets
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Posted to bioRxiv 14 Sep 2017

Minor allele frequency thresholds strongly affect population structure inference with genomic datasets
318 downloads genomics

Ethan B. Linck, C. J. Battey

Across the genome, the effects of different evolutionary processes and historical events can result in different classes of genetic variants (or alleles) characterized by their relative frequency in a given population. As a result, population genetic inference can be strongly affected by biases in laboratory and bioinformatics treatments that affect the site frequency spectrum, or SFS. Yet despite the widespread use of reduced-representation genomic datasets with nonmodel organisms, the potential consequences of these biases for downstream analyses remain poorly examined. Here, we assess the influence of minor allele frequency (MAF) thresholds implemented during variant detection on inference of population structure. We use simulated and empirical datasets to evaluate the effect of MAF thresholds on the ability to discriminate among populations and quantify admixture with both model-based and non-model-based clustering methods. We find model-based inference of population structure is highly sensitive to choice of MAF, and may be confounded by either including singletons or excluding all rare alleles. In contrast, non-model-based clustering is largely robust to MAF choice. Our results suggest that model-based inference of population structure can fail due to either natural demographic processes or assembly artifacts, with broad consequences for phylogeographic and population genetic studies using NGS data. We propose a simple hypothesis to explain this behavior and recommend a set of best practices for researchers seeking to describe population structure using reduced-representation libraries.

360: Ultrastructural details of mammalian chromosome architecture
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Posted to bioRxiv 17 May 2019

Ultrastructural details of mammalian chromosome architecture
318 downloads genomics

Nils Krietenstein, Sameer Abraham, Sergey Venev, Nezar Abdennur, Johan Gibcus, Tsung-Han Hsieh, Krishna Mohan Parsi, Liyan Yang, Rene Maehr, Leonid Mirny, Job Dekker, Oliver Rando

Over the past decade, 3C-related methods, complemented by increasingly detailed microscopic views of the nucleus, have provided unprecedented insights into chromosome folding in vivo. Here, to overcome the resolution limits inherent to the majority of genome-wide chromosome architecture mapping studies, we extend a recently-developed Hi-C variant, Micro-C, to map chromosome architecture at nucleosome resolution in human embryonic stem cells and fibroblasts. Micro-C maps robustly capture well-described features of mammalian chromosome folding including A/B compartment organization, topologically associating domains (TADs), and cis interaction peaks anchored at CTCF binding sites, while also providing a detailed 1-dimensional map of nucleosome positioning and phasing genome-wide. Compared to high-resolution in situ Hi-C, Micro-C exhibits substantially improved signal-to-noise with an order of magnitude greater dynamic range, enabling not only localization of domain boundaries with single-nucleosome accuracy, but also resolving more than 20,000 additional looping interaction peaks in each cell type. Intriguingly, many of these newly-identified peaks are localized along stripe patterns and form transitive grids, consistent with their anchors being pause sites impeding the process of cohesin-dependent loop extrusion. Together, our analyses provide the highest resolution maps of chromosome folding in human cells to date, and provide a valuable resource for studies of chromosome folding mechanisms.

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