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Rxivist combines preprints from bioRxiv with data from Twitter to help you find the papers being discussed in your field. Currently indexing 54,955 bioRxiv papers from 253,602 authors.

Most downloaded bioRxiv papers, since beginning of last month

in category cell biology

2,439 results found. For more information, click each entry to expand.

1: A Single Cell Transcriptomic Atlas Characterizes Aging Tissues in the Mouse
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Posted to bioRxiv 08 Jun 2019

A Single Cell Transcriptomic Atlas Characterizes Aging Tissues in the Mouse
1,603 downloads cell biology

The Tabula Muris Consortium, Angela Oliveira Pisco, Nicholas Schaum, Aaron McGeever, Jim Karkanias, Norma F. Neff, Spyros Darmanis, Tony Wyss-Coray, Stephen R. Quake

Aging is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. Despite rapid advances over recent years, many of the molecular and cellular processes which underlie progressive loss of healthy physiology are poorly understood. To gain a better insight into these processes we have created a single cell transcriptomic atlas across the life span of Mus musculus which includes data from 18 tissues and organs. We discovered cell-specific changes occurring across multiple cell types and organs, as well as age related changes in the cellular composition of different organs. Using single-cell transcriptomic data we were able to assess cell type specific manifestations of different hallmarks of aging, such as senescence, changes in the activity of metabolic pathways, depletion of stem-cell populations, genomic instability and the role of inflammation as well as other changes in the organism's immune system. This Tabula Muris Senis provides a wealth of new molecular information about how the most significant hallmarks of aging are reflected in a broad range of tissues and cell types.

2: Atlas of Subcellular RNA Localization Revealed by APEX-seq
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Posted to bioRxiv 26 Oct 2018

Atlas of Subcellular RNA Localization Revealed by APEX-seq
866 downloads cell biology

Furqan M Fazal, Shuo Han, Pornchai Kaewsapsak, Kevin R Parker, Jin Xu, Alistair N Boettiger, Howard Y. Chang, Alice Y. Ting

We introduce APEX-seq, a method for RNA sequencing based on spatial proximity to the peroxidase enzyme APEX2. APEX-seq in nine distinct subcellular locales produced a nanometer-resolution spatial map of the human transcriptome, revealing extensive and exquisite patterns of localization for diverse RNA classes and transcript isoforms. We uncover a radial organization of the nuclear transcriptome, which is gated at the inner surface of the nuclear pore for cytoplasmic export of processed transcripts. We identify two distinct pathways of messenger RNA localization to mitochondria, each associated with specific sets of transcripts for building complementary macromolecular machines within the organelle. APEX-seq should be widely applicable to many systems, enabling comprehensive investigations of the spatial transcriptome.

3: Single-Cell Signalling Analysis of Heterocellular Organoids
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Posted to bioRxiv 06 Jun 2019

Single-Cell Signalling Analysis of Heterocellular Organoids
671 downloads cell biology

Xiao Qin, Jahangir Sufi, Petra Vlckova, Pelagia Kyriakidou, Sophie E Acton, Vivian S. W. Li, Mark Nitz, Christopher J Tape

Organoids are biomimetic 3D models of healthy and diseased tissue. Despite their widespread adoption, methods to analyse cell-type specific signalling networks in organoids are absent. Here we report multiplexed single-cell analysis of post-translational modification (PTM) signalling networks in organoids by mass cytometry. Simultaneous analysis of 28 PTMs in >1 million single-organoid cells reveals cell-type and cell-state specific signalling networks in stem, Paneth, enteroendocrine, goblet, tuft cells, and enterocytes during intestinal organoid development. We demonstrate that Thiol-reactive Organoid Barcoding in situ (TOB is ) enables high-throughput multiplexed organoid signalling analysis in a single-tube − opening this technology to single-cell organoid screening. Comparison of colorectal cancer (CRC) oncogenic mutations ( Apc , Kras , and Trp53 ) and microenvironmental cues (fibroblasts and macrophages) revealed CRC driver-mutations mimic signalling normally provided by stromal cells. These results demonstrate mass cytometry is a powerful multiplexed single-cell technology for studying cell-specific signalling in organoid models of healthy and cancerous tissue.

4: Full-featured, real-time database searching platform enables fast and accurate multiplexed quantitative proteomics.
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Posted to bioRxiv 12 Jun 2019

Full-featured, real-time database searching platform enables fast and accurate multiplexed quantitative proteomics.
641 downloads cell biology

Devin K Schweppe, Jimmy K Eng, Derek Bailey, Ramin Rad, Qing Yu, Jose Navarrete-Perea, Edward L Huttlin, Brian K Erickson, Joao A Paulo, Steven P Gygi

Multiplexed quantitative analyses of complex proteomes enable deep biological insight. While a multitude of workflows have been developed for multiplexed analyses, the most quantitatively accurate method (SPS-MS3) suffers from long acquisition duty cycles. We built a new, real-time database search (RTS) platform, Orbiter, to combat the SPS-MS3 method's longer duty cycles. RTS with Orbiter enables the elimination of SPS-MS3 scans if no peptide matches to a given spectrum. With Orbiter's online proteomic analytical pipeline, which includes RTS and false discovery rate analysis, it was possible to process a single spectrum database search in less than 10 milliseconds. The result is a fast, functional means to identify peptide spectral matches using Comet, filter these matches, and more efficiently quantify proteins of interest. Importantly, the use of Comet for peptide spectral matching allowed for a fully featured search, including analysis of post-translational modifications, with well-known and extensively validated scoring. These data could then be used to trigger subsequent scans in an adaptive and flexible manner. In this work we tested the utility of this adaptive data acquisition platform to improve the efficiency and accuracy of multiplexed quantitative experiments. We found that RTS enabled a 2-fold increase in mass spectrometric data acquisition efficiency. Orbiter's RTS was able to quantify more than 8000 proteins across 10 proteomes in half the time of an SPS-MS3 analysis (18 hours for RTS, 36 hours for SPS-MS3).

5: Cellular and Molecular Probing of Intact Transparent Human Organs
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Posted to bioRxiv 21 May 2019

Cellular and Molecular Probing of Intact Transparent Human Organs
612 downloads cell biology

Shan Zhau, Mihail Ivilinov Todorov, Ruiyao Cai, Hanno Steinke, Elisabeth Kemter, Eckhard Wolf, Jan Lipfert, Ingo Bechmann, Ali Erturk

Optical tissue transparency permits cellular and molecular investigation of complex tissues in 3D, a fundamental need in biomedical sciences. Adult human organs are particularly challenging for this approach, owing to the accumulation of dense and sturdy molecules in decades-aged human tissues. Here, we introduce SHANEL method utilizing a new tissue permeabilization approach to clear and label stiff human organs. We used SHANEL to generate the first intact transparent adult human brain and kidney, and perform 3D histology using antibodies and dyes in centimeters depth. Thereby, we revealed structural details of the sclera, iris and suspensory ligament in the human eye, and the vessels and glomeruli in the human kidney. We also applied SHANEL on transgenic pig organs to map complex structures of EGFP expressing beta cells in >10 cm size pancreas. Overall, SHANEL is a robust and unbiased technology to chart the cellular and molecular architecture of intact large mammalian organs.

6: CRISPR interference-based platform for multimodal genetic screens in human iPSC-derived neurons
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Posted to bioRxiv 07 Jan 2019

CRISPR interference-based platform for multimodal genetic screens in human iPSC-derived neurons
447 downloads cell biology

Ruilin Tian, Mariam A Gachechiladze, Connor H Ludwig, Matthew T. Laurie, Jason Y Hong, Diane Nathaniel, Anika V Prabhu, Michael S Fernandopulle, Rajan Patel, Mehrnoosh Abshari, Michael E Ward, Martin Kampmann

CRISPR/Cas9-based functional genomics have transformed our ability to elucidate mammalian cell biology. However, most previous CRISPR-based screens were conducted in cancer cell lines, rather than healthy, differentiated cells. Here, we describe a CRISPR interference (CRISPRi)-based platform for genetic screens in human neurons derived from induced pluripotent stem cells (iPSCs). We demonstrate robust and durable knockdown of endogenous genes in such neurons, and present results from three complementary genetic screens. First, a survival-based screen revealed neuron-specific essential genes and genes that improved neuronal survival upon knockdown. Second, a screen with a single-cell transcriptomic readout uncovered several examples of genes whose knockdown had strikingly cell-type specific consequences. Third, a longitudinal imaging screen detected distinct consequences of gene knockdown on neuronal morphology. Our results highlight the power of unbiased genetic screens in iPSC-derived differentiated cell types and provide a platform for systematic interrogation of normal and disease states of neurons.

7: Actin chromobody imaging reveals sub-organellar actin dynamics
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Posted to bioRxiv 15 May 2019

Actin chromobody imaging reveals sub-organellar actin dynamics
395 downloads cell biology

Cara R. Schiavon, Tong Zhang, Bing Zhao, Leonardo R. Andrade, Melissa Wu, Tsung-Chang Sung, Yelena Dayn, Jasmine W. Feng, Omar A Quintero, Robert Grosse, Uri Manor

The actin cytoskeleton plays multiple critical roles in cells, from cell migration to organelle dynamics. The small and transient actin structures regulating organelle dynamics are difficult to detect with fluorescence microscopy. We developed an approach using fluorescent protein-tagged actin nanobodies targeted to organelle membranes to enable live cell imaging of previously undetected sub-organellar actin dynamics with high spatiotemporal resolution. These probes reveal that ER-associated actin drives fission of multiple organelles including mitochondria, endosomes, lysosomes, peroxisomes, and the Golgi. ![Figure][1]</img> [1]: pending:yes

8: Fungal Feature Tracker (FFT): A tool for quantitatively characterizing the morphology and growth of filamentous fungi
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Posted to bioRxiv 04 Jun 2019

Fungal Feature Tracker (FFT): A tool for quantitatively characterizing the morphology and growth of filamentous fungi
362 downloads cell biology

Guillermo Vidal-Diez de Ulzurrun, Tsung-Yu Huang, Ching-Wen Chang, Hung-Che Lin, Yen-Ping Hsueh

Filamentous fungi are ubiquitous in nature and serve as important biological models in various scientific fields including genetics, cell biology, ecology, evolution, and chemistry. A significant obstacle in studying filamentous fungi is the lack of tools for characterizing their growth and morphology in an efficient and quantitative manner. Consequently, assessments of the growth of filamentous fungi are often subjective and imprecise. In order to remedy this problem, we developed Fungal Feature Tracker (FFT), a user-friendly software comprised of different image analysis tools to automatically quantify different fungal characteristics, such as spore number, spore morphology, and measurements of total length, number of hyphal tips and the area covered by the mycelium. In addition, FFT can recognize and quantify specialized structures such as the traps generated by nematode-trapping fungi, which could be tuned to quantify other distinctive fungal structures in different fungi. We present a detailed characterization and comparison of a few fungal species as a case study to demonstrate the capabilities and potential of our software. Using FFT, we were able to quantify various features at strain and species level, such as mycelial growth over time and the length and width of spores, which would be difficult to track using classical approaches. In summary, FFT is a powerful tool that enables quantitative measurements of fungal features and growth, allowing objective and precise characterization of fungal phenotypes.

9: Light-regulated collective contractility in a multicellular choanoflagellate
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Posted to bioRxiv 06 Jun 2019

Light-regulated collective contractility in a multicellular choanoflagellate
355 downloads cell biology

Thibuat Brunet, Ben T. Larson, Tess Linden, Mark J. A. Vermeij, Kent L. McDonald, Nicole King

Collective cell contractions that generate global tissue deformations are a signature feature of animal movement and morphogenesis. Nonetheless, the ancestry of collective contractility in animals remains mysterious. While surveying the Caribbean island of Curaçao for choanoflagellates, the closest living relatives of animals, we isolated a previously undescribed species (here named Choanoeca flexa sp. nov.), that forms multicellular cup-shaped colonies. The colonies rapidly invert their curvature in response to changing light levels, which they detect through a rhodopsin-cGMP pathway. Inversion requires actomyosin-mediated apical contractility and allows alternation between feeding and swimming behavior. C. flexa thus rapidly converts sensory inputs directly into multicellular contractions. In this respect, it may inform reconstructions of hypothesized animal ancestors that existed before the evolution of specialized sensory and contractile cells.

10: Multiscale activity imaging in the mammary gland reveals how oxytocin enables lactation
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Posted to bioRxiv 03 Jun 2019

Multiscale activity imaging in the mammary gland reveals how oxytocin enables lactation
348 downloads cell biology

Alexander J Stevenson, Gilles Vanwalleghem, Teneale A. Stewart, Nicholas D Condon, Bethan Lloyd-Lewis, Natascia Marino, James W Putney, Ethan K. Scott, Adam D Ewing, Felicity M Davis

The mammary epithelium is indispensable for the continued survival of more than 5000 mammalian species. For some, the volume of milk ejected in a single day exceeds their entire blood volume. Here, we unveil the spatiotemporal properties of physiological signals that orchestrate milk ejection. Using quantitative, multidimensional imaging of mammary cell ensembles, we reveal how stimulus-evoked Ca2+ oscillations couple to contraction in basal epithelial cells. Moreover, we show that Ca2+-dependent contractions generate the requisite force to physically-deform the innermost layer of luminal cells, forcing them to discharge the fluid that they produced and housed. Through the collective action of thousands of these biological positive-displacement pumps, each linked to a contractile ductal network, milk is delivered into the mouth of the dependent neonate, seconds after the command.

11: Highly multiplexed in situ protein imaging with signal amplification by Immuno-SABER
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Posted to bioRxiv 28 Dec 2018

Highly multiplexed in situ protein imaging with signal amplification by Immuno-SABER
337 downloads cell biology

Sinem K. Saka, Yu Wang, Jocelyn Y. Kishi, Allen Zhu, Yitian Zeng, Wenxin Xie, Koray Kirli, Clarence Yapp, Marcelo Cicconet, Brian J. Beliveau, Sylvain W Lapan, Siyuan Yin, Millicent Lin, Edward S Boyden, Pascal S Kaeser, German Pihan, George M Church, Peng Yin

Probing the molecular organization of tissues requires in situ analysis by microscopy. However current limitations in multiplexing, sensitivity, and throughput collectively constitute a major barrier for comprehensive single-cell profiling of proteins. Here, we report Immunostaining with Signal Amplification By Exchange Reaction (Immuno-SABER), a rapid, highly multiplexed signal amplification method that simultaneously tackles these key challenges. Immuno-SABER utilizes DNA-barcoded antibodies and provides a method for highly multiplexed signal amplification via modular orthogonal DNA concatemers generated by Primer Exchange Reaction. This approach offers the capability to preprogram and control the amplification level independently for multiple targets without in situ enzymatic reactions, and the intrinsic scalability to rapidly amplify and image a large number of protein targets. We validated our approach in diverse sample types including cultured cells, cryosections, FFPE sections, and whole mount tissues. We demonstrated independently tunable 5-180-fold amplification for multiple targets, covering the full signal range conventionally achieved by secondary antibodies to tyramide signal amplification, as well as simultaneous signal amplification for 10 different proteins using standard equipment and workflow. We further combined Immuno-SABER with Expansion Microscopy to enable rapid and highly multiplexed super-resolution tissue imaging. Overall, Immuno-SABER presents an effective and accessible platform for rapid, multiplexed imaging of proteins across scales with high sensitivity.

12: Functional classification of noncoding RNAs associated with distinct histone modifications by PIRCh-seq
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Posted to bioRxiv 11 Jun 2019

Functional classification of noncoding RNAs associated with distinct histone modifications by PIRCh-seq
325 downloads cell biology

Jingwen Fang, Qing Ma, Ci Chu, Beibei Huang, Lingjie Li, Pengfei Cai, Pedro J. Batista, Karen Erisse Martin Tolentino, Jin Xu, Rui Li, Pengcheng Du, Kun Qu, Howard Chang

Many long noncoding RNAs (lncRNAs) regulate gene transcription through binding to histone modification complexes. Therefore, a comprehensive study of nuclear RNAs in a histone modification-specific manner is critical to understand their regulatory mechanisms. Here we develop a method named Profiling Interacting RNAs on Chromatin by deep sequencing (PIRCh-seq), in which we profile chromatin-associated transcriptome in 5 different cell types using antibodies recognizing histone H3 and 6 distinct histone modifications associated with active or repressive chromatin states. PIRCh-seq identified chromatin-associated RNAs with substantially less contamination by nascent transcripts, as compared to existing methods. We classified chromatin-enriched lncRNAs into 6 functional groups based on the patterns of their association with specific histone modifications. LncRNAs were enriched with different chromatin modifications in different cell types, suggesting lncRNAs' regulation may also be cell type-specific. By integrating profiles of RNA secondary structure and RNA m6A modification, we found that RNA bases which bind to chromatin tend to be more single stranded. We discovered hundreds of allele-specific RNA-chromatin interactions, nominating specific single nucleotide variants that alter RNA association with chromatin. These results provide a unique resource to globally study the functions of chromatin-associated lncRNAs and elucidate the basic mechanisms of chromatin-RNA interaction.

13: Preparation of Organ Scaffolds by Decellularization of Pancreas and Re-functionalization
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Posted to bioRxiv 07 Jan 2019

Preparation of Organ Scaffolds by Decellularization of Pancreas and Re-functionalization
311 downloads cell biology

Uday Chandrika K, Rekha Tripathi, Avinash Raj T, Sairam N, Vasundhara Kamineni Parlikar, Swami VB, Nandini Rangaraj, Mahesh Kumar Jerald, Shashi Singh

Extracellular matrix of each tissue is unique in composition, architecture and finer details that support the very identity of the organ by regulating the status/character of the cells within it. Tissue engineering centers around creating a niche similar to the natural one, with a purpose of developing an organ/oid. In this study, whole organ decellularization of pancreas was attempted followed by reseeding it with adult mesenchymal stem cells. Decellularization completely removes cells leaving behind extracellular matrix rich scaffold. After reseeding, mesenchymal stem cells differentiate into pancreas specific cells. Upon transplantation of recellularized pancreas in streptozotocin induced diabetic mice, this organ was capable of restoring its histomorphology and normal functioning. Restoration of endocrine islets, the exocrine acinar region, and vascular network was seen in transplanted pancreas. The entire process of functional recovery took about 20 days when the mice demonstrated glucoregulation, though none achieved gluconormalization. Transplanted mice upon feeding show insulin and c-peptide in circulation. This process demonstrates that natural scaffolds of soft organs can be refunctionalized using recipients cells to counter immune problems arising due to organ transplantation.

14: Unconventional cell division cycles from marine-derived yeasts
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Posted to bioRxiv 02 Jun 2019

Unconventional cell division cycles from marine-derived yeasts
300 downloads cell biology

Lorna M. Y. Mitchison-Field, José M. Vargas-Muñiz, Benjamin M Stormo, Ellysa J. D. Vogt, Sarah Van Dierdonck, Christoph Ehrlich, Daniel Lew, Christine Field, Amy Gladfelter

Fungi have been found in every marine habitat that has been explored, however, the diversity and functions of fungi in the ocean are poorly understood. In this study, fungi were cultured from the marine environment in the vicinity of Woods Hole, MA, USA including from plankton, sponge and coral. Our sampling resulted in 36 unique species across 20 genera. We observed many isolates by time-lapse differential interference contrast (DIC) microscopy and analyzed modes of growth and division. Several black yeasts displayed highly unconventional cell division cycles compared to those of traditional model yeast systems. Black yeasts have been found in habitats inhospitable to other life and are known for halotolerance, virulence, and stress-resistance. We find that this group of yeasts also shows remarkable plasticity in terms of cell size control, modes of cell division, and cell polarity. Unexpected behaviors include division through a combination of fission and budding, production of multiple simultaneous buds, and cell division by sequential orthogonal septations. These marine-derived yeasts reveal alternative mechanisms for cell division cycles that seem likely to expand the repertoire of rules established from classic model system yeasts.

15: Mammary mechanobiology: PIEZO1 mechanically-activated ion channels in lactation and involution
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Posted to bioRxiv 26 May 2019

Mammary mechanobiology: PIEZO1 mechanically-activated ion channels in lactation and involution
289 downloads cell biology

Teneale A. Stewart, Katherine Hughes, Alexander J Stevenson, Natascia Marino, Adler L Ju, Michael Morehead, Felicity M Davis

A mother's ability to produce a nutritionally-complete neonatal food source has provided a powerful evolutionary advantage to mammals. Milk production by secretory mammary epithelial cells is adaptive, its release is exquisitely timed and its own glandular stagnation with the permanent cessation of suckling triggers the programmed cell death and tissue remodeling that enables female mammals to nurse successive progeny. Both chemical and mechanical signals control epithelial expansion, function and remodeling. Despite this duality of input, however, the nature and function of mechanical forces in the mammary gland remain unknown. Here, we characterize the mammary force landscape and the capacity of luminal and basal epithelial cells to experience and exert force. We explore the molecular instruments for force-sensing in the mammary gland and the physiological requirement for PIEZO1 in lactation and involution. Our study supports the existence of a multifaceted system of chemical and mechanical sensing in the mammary gland, and a protective redundancy that ensures continued lactational competence and offspring survival.

16: Negligible-Cost and Weekend-Free Chemically Defined Human iPSC Culture
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Posted to bioRxiv 28 Jun 2019

Negligible-Cost and Weekend-Free Chemically Defined Human iPSC Culture
288 downloads cell biology

Hui-Hsuan Kuo, Xiaozhi Gao, Jean-Marc DeKeyser, K. Ashley Fetterman, Emily A Pinheiro, Carly J Weddle, Michael V Orman, Marisol Romero-Tejeda, Mariam Jouni, Malorie Blancard, Tarek Magdy, Conrad Epting, Alfred L George, Paul W Burridge

Human induced pluripotent stem cell (hiPSC) culture has become routine, yet pluripotent cell media costs, frequent media changes, and reproducibility of differentiation have remained restrictive, limiting the potential for large-scale projects. Here, we describe the formulation of a novel hiPSC culture medium (B8) as a result of the exhaustive optimization of medium constituents and concentrations, establishing the necessity and relative contributions of each component to the pluripotent state and cell proliferation. B8 eliminates 97% of the costs of commercial media, made possible primarily by the in-lab generation of three E. coli -expressed, codon-optimized recombinant proteins: an engineered form of fibroblast growth factor 2 (FGF2) with improved thermostability (FGF2-G3); transforming growth factor β3 (TGFβ3) -a more potent TGFβ able to be expressed in E. coli ; and a derivative of neuregulin 1 (NRG1) containing the EGF-like domain. The B8 formula is specifically optimized for fast growth and robustness at low seeding densities. We demonstrated the derivation of 29 hiPSC lines in B8 as well as maintenance of pluripotency long-term, while conserving karyotype stability. This formula also allows a weekend-free feeding schedule without sacrificing growth rate or capacity for differentiation. Thus, this simple, cost-effective, and open source B8 media, will enable large hiPSC disease modeling projects such as those being performed in pharmacogenomics and large-scale cell production required for regenerative medicine.

17: ESCRT machinery mediates selective microautophagy of endoplasmic reticulum
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Posted to bioRxiv 05 Jun 2019

ESCRT machinery mediates selective microautophagy of endoplasmic reticulum
271 downloads cell biology

Jasmin Schaefer, Julia Schessner, Peter Bircham, Takuma Tsuji, Charlotta Funaya, Katharina Schaeff, Giulia Ruffini, Dimitrios Papagiannidis, Michael Knop, Toyoshi Fujimoto, Sebastian Schuck

ER-phagy, the selective autophagy of endoplasmic reticulum (ER), safeguards organelle homeostasis by eliminating misfolded proteins and regulating ER size. ER-phagy can occur by macroautophagic and microautophagic mechanisms. While dedicated machinery for macro-ER-phagy has been discovered, the molecules and mechanisms mediating micro-ER-phagy remain unknown. Here, we first show that micro-ER-phagy in yeast involves the conversion of stacked cisternal ER into multilamellar ER whorls during microautophagic uptake into lysosomes. Second, we identify the conserved Nem1-Spo7 phosphatase complex and ESCRT proteins as key components for micro-ER-phagy. Third, we demonstrate that macro- and micro-ER-phagy are parallel pathways with distinct molecular requirements. Finally, we provide evidence that ESCRT proteins directly function in scission of the lysosomal membrane to complete the microautophagic uptake of ER. These findings establish a framework for a mechanistic understanding of micro-ER-phagy and, thus, a comprehensive appreciation of the role of autophagy in ER homeostasis.

18: Ultrastructure of the axonal periodic scaffold reveals a braid-like organization of actin rings
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Posted to bioRxiv 13 May 2019

Ultrastructure of the axonal periodic scaffold reveals a braid-like organization of actin rings
265 downloads cell biology

Stephane Vassilopoulos, Solène Gibaud, Angélique Jimenez, Ghislaine Caillol, Christophe Leterrier

Recent super-resolution microscopy studies have unveiled a periodic scaffold of actin rings regularly spaced by spectrins under the plasma membrane of axons. However, ultrastructural details are unknown, limiting a molecular and mechanistic understanding of these enigmatic structures. Here, we combine platinum-replica electron and optical super-resolution microscopy to investigate the cortical cytoskeleton of axons at the ultrastructural level. We resolve actin rings as braids made of two long, intertwined actin filaments connected by a dense mesh of aligned spectrins. This molecular arrangement contrasts with the currently assumed model of actin rings made of short, capped actin filaments. We propose that braided rings explain the stability of the actin-spectrin scaffold and ultimately help preserving the axon integrity.

19: Single Cell Analysis Reveals Immune Cell-Adipocyte Crosstalk Regulating the Transcription of Thermogenic Adipocytes
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Posted to bioRxiv 13 Jun 2019

Single Cell Analysis Reveals Immune Cell-Adipocyte Crosstalk Regulating the Transcription of Thermogenic Adipocytes
241 downloads cell biology

Prashant Rajbhandari, Douglas Arneson, An-Chieh Feng, In Sook Ahn, Graciel Diamante, Nima Zaghari, Brandon Thomas, Laurent Vergnes, Stephen Lee, Karen Reue, Stephen Smale, Xia Yang, Peter Tontonoz

Immune cells are vital constituents of the adipose microenvironment that influence both local and systemic lipid metabolism. Mice lacking IL10 have enhanced thermogenesis, but the roles of specific cell types in the metabolic response to IL10 remain to be defined. We demonstrate here that selective loss of IL10 receptor a in adipocytes recapitulates the beneficial effects of global IL10 deletion, and that local crosstalk between IL10-producing immune cells and adipocytes is a determinant of thermogenesis and systemic energy balance. Single Nuclei Adipocyte RNA-sequencing (SNAP-seq) of subcutaneous adipose tissue defined a metabolically-active mature adipocyte subtype characterized by robust expression of genes involved in thermogenesis whose transcriptome was selectively responsive to IL10Ra deletion. Furthermore, single-cell transcriptomic analysis of adipose stromal populations identified lymphocytes as a key source of IL10 production in response to thermogenic stimuli. These findings implicate adaptive immune cell-adipocyte communication in the maintenance of adipose subtype identity and function.

20: Phase separation of TAZ compartmentalizes the transcription machinery to promote gene expression
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Posted to bioRxiv 14 Jun 2019

Phase separation of TAZ compartmentalizes the transcription machinery to promote gene expression
240 downloads cell biology

Tiantian Wu, Yi Lu, Orit Gutman, Huasong Lu, Qiang Zhou, Yoav I. Henis, Kunxin Luo

TAZ promotes cell proliferation, development, and tumorigenesis by regulating target gene transcription. However, how TAZ orchestrates the transcriptional responses remains poorly defined. Here we demonstrate that TAZ forms nuclear condensates via liquid-liquid phase separation to compartmentalize its DNA binding co-factor TEAD4, the transcription co-activators BRD4 and MED1 and the transcription elongation factor CDK9 for activation of gene expression. TAZ, but not its paralog YAP, forms phase-separated droplets in vitro and liquid-like nuclear condensates in vivo, and this ability is negatively regulated by Hippo signaling via LATS-mediated phosphorylation and mediated by the coiled-coil domain. Deletion of the TAZ coiled-coil domain or substitution with the YAP coiled-coil domain does not affect the interaction of TAZ with its partners, but prevents its phase separation and more importantly, its ability to induce target gene expression. Thus, our study identifies a novel mechanism for the transcriptional activation by TAZ and demonstrates for the first time that pathway-specific transcription factors also engage the phase separation mechanism for efficient transcription activation.

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