Showing papers by "Howard Hughes Medical Institute published in 2015"
TL;DR: The 1000 Genomes Project set out to provide a comprehensive description of common human genetic variation by applying whole-genome sequencing to a diverse set of individuals from multiple populations, and has reconstructed the genomes of 2,504 individuals from 26 populations using a combination of low-coverage whole-generation sequencing, deep exome sequencing, and dense microarray genotyping.
Abstract: The 1000 Genomes Project set out to provide a comprehensive description of common human genetic variation by applying whole-genome sequencing to a diverse set of individuals from multiple populations. Here we report completion of the project, having reconstructed the genomes of 2,504 individuals from 26 populations using a combination of low-coverage whole-genome sequencing, deep exome sequencing, and dense microarray genotyping. We characterized a broad spectrum of genetic variation, in total over 88 million variants (84.7 million single nucleotide polymorphisms (SNPs), 3.6 million short insertions/deletions (indels), and 60,000 structural variants), all phased onto high-quality haplotypes. This resource includes >99% of SNP variants with a frequency of >1% for a variety of ancestries. We describe the distribution of genetic variation across the global sample, and discuss the implications for common disease studies.
12,661 citations
TL;DR: Drop-seq will accelerate biological discovery by enabling routine transcriptional profiling at single-cell resolution by separating them into nanoliter-sized aqueous droplets, associating a different barcode with each cell's RNAs, and sequencing them all together.
5,506 citations
Massachusetts Institute of Technology1, Broad Institute2, University of California, Los Angeles3, University of British Columbia4, Baylor College of Medicine5, Howard Hughes Medical Institute6, University of Washington7, Ludwig Institute for Cancer Research8, University of California, San Francisco9, University of Connecticut10, University of Zagreb11, University of Texas at Austin12, Washington University in St. Louis13, University of Queensland14, Harvard University15, Cold Spring Harbor Laboratory16, University of Southern California17, University of California, Santa Cruz18, Simon Fraser University19, Morgridge Institute for Research20, University of Texas at Dallas21, National Institutes of Health22
TL;DR: It is shown that disease- and trait-associated genetic variants are enriched in tissue-specific epigenomic marks, revealing biologically relevant cell types for diverse human traits, and providing a resource for interpreting the molecular basis of human disease.
Abstract: The reference human genome sequence set the stage for studies of genetic variation and its association with human disease, but epigenomic studies lack a similar reference. To address this need, the NIH Roadmap Epigenomics Consortium generated the largest collection so far of human epigenomes for primary cells and tissues. Here we describe the integrative analysis of 111 reference human epigenomes generated as part of the programme, profiled for histone modification patterns, DNA accessibility, DNA methylation and RNA expression. We establish global maps of regulatory elements, define regulatory modules of coordinated activity, and their likely activators and repressors. We show that disease- and trait-associated genetic variants are enriched in tissue-specific epigenomic marks, revealing biologically relevant cell types for diverse human traits, and providing a resource for interpreting the molecular basis of human disease. Our results demonstrate the central role of epigenomic information for understanding gene regulation, cellular differentiation and human disease.
5,037 citations
TL;DR: Modifications to the CTFFIND algorithm are described which make it significantly faster and more suitable for use with images collected using modern technologies such as dose fractionation and phase plates.
3,512 citations
01 May 2015
TL;DR: Drop-seq as discussed by the authors analyzes mRNA transcripts from thousands of individual cells simultaneously while remembering transcripts' cell of origin, and identifies 39 transcriptionally distinct cell populations, creating a molecular atlas of gene expression for known retinal cell classes and novel candidate cell subtypes.
Abstract: Cells, the basic units of biological structure and function, vary broadly in type and state. Single-cell genomics can characterize cell identity and function, but limitations of ease and scale have prevented its broad application. Here we describe Drop-seq, a strategy for quickly profiling thousands of individual cells by separating them into nanoliter-sized aqueous droplets, associating a different barcode with each cell's RNAs, and sequencing them all together. Drop-seq analyzes mRNA transcripts from thousands of individual cells simultaneously while remembering transcripts' cell of origin. We analyzed transcriptomes from 44,808 mouse retinal cells and identified 39 transcriptionally distinct cell populations, creating a molecular atlas of gene expression for known retinal cell classes and novel candidate cell subtypes. Drop-seq will accelerate biological discovery by enabling routine transcriptional profiling at single-cell resolution. VIDEO ABSTRACT.
3,365 citations
TL;DR: In a unified mechanism of m(6)A-based regulation in the cytoplasm, YTHDF2-mediated degradation controls the lifetime of target transcripts, whereasYTHDF1-mediated translation promotion increases translation efficiency, ensuring effective protein production from dynamic transcripts that are marked by m( 6)A.
2,179 citations
TL;DR: A fine-mapping algorithm is developed to identify candidate causal variants for 21 autoimmune diseases from genotyping data, and it is found that most non-coding risk variants, including those that alter gene expression, affect non-canonical sequence determinants not well-explained by current gene regulatory models.
Abstract: Genome-wide association studies have identified loci underlying human diseases, but the causal nucleotide changes and mechanisms remain largely unknown. Here we developed a fine-mapping algorithm to identify candidate causal variants for 21 autoimmune diseases from genotyping data. We integrated these predictions with transcription and cis-regulatory element annotations, derived by mapping RNA and chromatin in primary immune cells, including resting and stimulated CD4(+) T-cell subsets, regulatory T cells, CD8(+) T cells, B cells, and monocytes. We find that ∼90% of causal variants are non-coding, with ∼60% mapping to immune-cell enhancers, many of which gain histone acetylation and transcribe enhancer-associated RNA upon immune stimulation. Causal variants tend to occur near binding sites for master regulators of immune differentiation and stimulus-dependent gene activation, but only 10-20% directly alter recognizable transcription factor binding motifs. Rather, most non-coding risk variants, including those that alter gene expression, affect non-canonical sequence determinants not well-explained by current gene regulatory models.
1,622 citations
TL;DR: This report reports multiplexed error-robust FISH (MERFISH), a single-molecule imaging method that allows thousands of RNA species to be imaged in single cells by using combinatorial FISH labeling with encoding schemes capable of detecting and/or correcting errors.
Abstract: INTRODUCTION: The copy number and in- tracellular localization of RNA are important regulators of gene expression. Measurement of these properties at the transcriptome scale in single cells will give answers to many ques- tions related to gene expression and regulation. Single-molecule RNA imaging approaches, such as single-molecule fluorescence in situ hybrid- ization(smFISH), are powerful toolsforcount- ing and mappingRNA; however, the number of RNA species that can be simultaneously im- aged in individual cells has been limited. This makes it challenging to perform transcriptomic analysis of single cells in a spatially resolved manner. Here, we report multiplexed error- robust FISH (MERFISH), a single-molecule im- aging method that allows thousands of RNA species to be imaged in single cells by using combinatorial FISH labeling with encoding schemes capable of detecting and/or correct- ing errors. RATIONALE: We labeled each cellular RNA with a set of encoding probes, which contain targeting sequences that bind the RNA and readout sequences that bind fluorescently la- beled readout probes. Each RNA species is encodedwithaparticular combinationofread- out sequences. We used successive rounds of hybridization and imaging, each with a differ- ent readout probe, to identify the readout se- quences bound to each RNA and to decode the RNA. In principle, combinatorial labeling al- lows the number of detectable RNA species to
1,576 citations
TL;DR: It is shown that the lifetime risk of cancers of many different types is strongly correlated with the total number of divisions of the normal self-renewing cells maintaining that tissue’s homeostasis, suggesting that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions.
Abstract: Some tissue types give rise to human cancers millions of times more often than other tissue types. Although this has been recognized for more than a century, it has never been explained. Here, we show that the lifetime risk of cancers of many different types is strongly correlated (0.81) with the total number of divisions of the normal self-renewing cells maintaining that tissue’s homeostasis. These results suggest that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions. The majority is due to “bad luck,” that is, random mutations arising during DNA replication in normal, noncancerous stem cells. This is important not only for understanding the disease but also for designing strategies to limit the mortality it causes.
1,519 citations
University of Adelaide1, Harvard University2, Broad Institute3, Howard Hughes Medical Institute4, University of Mainz5, Max Planck Society6, University of Tübingen7, Hungarian Academy of Sciences8, Stockholm University9, Facultad de Filosofía y Letras10, The Heritage Foundation11, University of Basel12, Autonomous University of Barcelona13, University of Valladolid14, Hartwick College15
TL;DR: In this paper, the authors generated genome-wide data from 69 Europeans who lived between 8,000-3,000 years ago by enriching ancient DNA libraries for a target set of almost 400,000 polymorphisms.
Abstract: We generated genome-wide data from 69 Europeans who lived between 8,000-3,000 years ago by enriching ancient DNA libraries for a target set of almost 400,000 polymorphisms. Enrichment of these positions decreases the sequencing required for genome-wide ancient DNA analysis by a median of around 250-fold, allowing us to study an order of magnitude more individuals than previous studies and to obtain new insights about the past. We show that the populations of Western and Far Eastern Europe followed opposite trajectories between 8,000-5,000 years ago. At the beginning of the Neolithic period in Europe, ∼8,000-7,000 years ago, closely related groups of early farmers appeared in Germany, Hungary and Spain, different from indigenous hunter-gatherers, whereas Russia was inhabited by a distinctive population of hunter-gatherers with high affinity to a ∼24,000-year-old Siberian. By ∼6,000-5,000 years ago, farmers throughout much of Europe had more hunter-gatherer ancestry than their predecessors, but in Russia, the Yamnaya steppe herders of this time were descended not only from the preceding eastern European hunter-gatherers, but also from a population of Near Eastern ancestry. Western and Eastern Europe came into contact ∼4,500 years ago, as the Late Neolithic Corded Ware people from Germany traced ∼75% of their ancestry to the Yamnaya, documenting a massive migration into the heartland of Europe from its eastern periphery. This steppe ancestry persisted in all sampled central Europeans until at least ∼3,000 years ago, and is ubiquitous in present-day Europeans. These results provide support for a steppe origin of at least some of the Indo-European languages of Europe.
1,332 citations
TL;DR: It is found that m6A alters the local structure in mRNA and long non-coding RNA (lncRNA) to facilitate binding of heterogeneous nuclear ribonucleoprotein C (HNRNPC), an abundant nuclear RNA-binding protein responsible for pre-mRNA processing.
Abstract: RNA-binding proteins control many aspects of cellular biology through binding single-stranded RNA binding motifs (RBMs). However, RBMs can be buried within their local RNA structures, thus inhibiting RNA-protein interactions. N(6)-methyladenosine (m(6)A), the most abundant and dynamic internal modification in eukaryotic messenger RNA, can be selectively recognized by the YTHDF2 protein to affect the stability of cytoplasmic mRNAs, but how m(6)A achieves its wide-ranging physiological role needs further exploration. Here we show in human cells that m(6)A controls the RNA-structure-dependent accessibility of RBMs to affect RNA-protein interactions for biological regulation; we term this mechanism 'the m(6)A-switch'. We found that m(6)A alters the local structure in mRNA and long non-coding RNA (lncRNA) to facilitate binding of heterogeneous nuclear ribonucleoprotein C (HNRNPC), an abundant nuclear RNA-binding protein responsible for pre-mRNA processing. Combining photoactivatable-ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP) and anti-m(6)A immunoprecipitation (MeRIP) approaches enabled us to identify 39,060 m(6)A-switches among HNRNPC-binding sites; and global m(6)A reduction decreased HNRNPC binding at 2,798 high-confidence m(6)A-switches. We determined that these m(6)A-switch-regulated HNRNPC-binding activities affect the abundance as well as alternative splicing of target mRNAs, demonstrating the regulatory role of m(6)A-switches on gene expression and RNA maturation. Our results illustrate how RNA-binding proteins gain regulated access to their RBMs through m(6)A-dependent RNA structural remodelling, and provide a new direction for investigating RNA-modification-coded cellular biology.
École Polytechnique Fédérale de Lausanne1, MIND Institute2, Technical University of Madrid3, Spanish National Research Council4, Hebrew University of Jerusalem5, Howard Hughes Medical Institute6, Imperial College London7, Yale University8, University of Debrecen9, King Juan Carlos University10, Karolinska Institutet11, University of Nottingham12, Tufts University13, Wenzhou Medical College14
TL;DR: A first-draft digital reconstruction of the microcircuitry of somatosensory cortex of juvenile rat is presented, finding a spectrum of network states with a sharp transition from synchronous to asynchronous activity, modulated by physiological mechanisms.
TL;DR: It is demonstrated that the disordered regions of key RNP granule components and the full-length granule protein hnRNPA1 can phase separate in vitro, producing dynamic liquid droplets.
TL;DR: It is reported that common cationic lipid nucleic acid transfection reagents can potently deliver proteins that are fused to negatively supercharged proteins, that contain natural anionic domains or that natively bind to anionic nucleic acids.
Abstract: Efficient intracellular delivery of proteins is needed to fully realize the potential of protein therapeutics. Current methods of protein delivery commonly suffer from low tolerance for serum, poor endosomal escape and limited in vivo efficacy. Here we report that common cationic lipid nucleic acid transfection reagents can potently deliver proteins that are fused to negatively supercharged proteins, that contain natural anionic domains or that natively bind to anionic nucleic acids. This approach mediates the potent delivery of nM concentrations of Cre recombinase, TALE- and Cas9-based transcription activators, and Cas9:sgRNA nuclease complexes into cultured human cells in media containing 10% serum. Delivery of unmodified Cas9:sgRNA complexes resulted in up to 80% genome modification with substantially higher specificity compared to DNA transfection. This approach also mediated efficient delivery of Cre recombinase and Cas9:sgRNA complexes into the mouse inner ear in vivo, achieving 90% Cre-mediated recombination and 20% Cas9-mediated genome modification in hair cells.
TL;DR: Using high-throughput affinity-purification mass spectrometry, BioPlex is used to identify interacting partners for 2,594 human proteins in HEK293T cells and reveals associations among thousands of protein domains, suggesting a basis for examining structurally related proteins.
University of California, San Francisco1, University of Chicago2, Yale University3, Harvard University4, Broad Institute5, Bilkent University6, Carnegie Mellon University7, Peking University8, Icahn School of Medicine at Mount Sinai9, University of Pittsburgh10, Stanford University11, Baylor College of Medicine12, University of California, Los Angeles13, Oregon Health & Science University14, Cornell University15, University of Michigan16, Brown University17, Vanderbilt University18, Howard Hughes Medical Institute19, Geisinger Health System20, University of Illinois at Chicago21
TL;DR: Analysis of de novo CNVs from the full Simons Simplex Collection replicates prior findings of strong association with autism spectrum disorders (ASDs) and confirms six risk loci, including 6 CNV regions.
TL;DR: It is shown that moderate mtDNA stress elicited by TFAM deficiency engages cytosolic antiviral signalling to enhance the expression of a subset of interferon-stimulated genes, and it is suggested that cellular monitoring of mtDNA homeostasis cooperates with canonical virus sensing mechanisms to fully engage antiviral innate immunity.
Abstract: Mitochondrial DNA (mtDNA) is normally present at thousands of copies per cell and is packaged into several hundred higher-order structures termed nucleoids The abundant mtDNA-binding protein TFAM (transcription factor A, mitochondrial) regulates nucleoid architecture, abundance and segregation Complete mtDNA depletion profoundly impairs oxidative phosphorylation, triggering calcium-dependent stress signalling and adaptive metabolic responses However, the cellular responses to mtDNA instability, a physiologically relevant stress observed in many human diseases and ageing, remain poorly defined Here we show that moderate mtDNA stress elicited by TFAM deficiency engages cytosolic antiviral signalling to enhance the expression of a subset of interferon-stimulated genes Mechanistically, we find that aberrant mtDNA packaging promotes escape of mtDNA into the cytosol, where it engages the DNA sensor cGAS (also known as MB21D1) and promotes STING (also known as TMEM173)-IRF3-dependent signalling to elevate interferon-stimulated gene expression, potentiate type I interferon responses and confer broad viral resistance Furthermore, we demonstrate that herpesviruses induce mtDNA stress, which enhances antiviral signalling and type I interferon responses during infection Our results further demonstrate that mitochondria are central participants in innate immunity, identify mtDNA stress as a cell-intrinsic trigger of antiviral signalling and suggest that cellular monitoring of mtDNA homeostasis cooperates with canonical virus sensing mechanisms to fully engage antiviral innate immunity
TL;DR: An improved transcriptional regulator obtained through the rational design of a tripartite activator, VP64-p65-Rta (VPR), fused to nuclease-null Cas9 is described and demonstrated in activating endogenous coding and noncoding genes and stimulating neuronal differentiation of human induced pluripotent stem cells (iPSCs).
Abstract: The RNA-guided nuclease Cas9 can be reengineered as a programmable transcription factor. However, modest levels of gene activation have limited potential applications. We describe an improved transcriptional regulator obtained through the rational design of a tripartite activator, VP64-p65-Rta (VPR), fused to nuclease-null Cas9. We demonstrate its utility in activating endogenous coding and noncoding genes, targeting several genes simultaneously and stimulating neuronal differentiation of human induced pluripotent stem cells (iPSCs).
TL;DR: Inspired by molecular modeling, the N,N-dimethylamino substituents in tetramethylrhodamine are replaced with four-membered azetidine rings, which doubles the quantum efficiency and improves the photon yield of the dye in applications ranging from in vitro single-molecule measurements to super-resolution imaging.
Abstract: Specific labeling of biomolecules with bright fluorophores is the keystone of fluorescence microscopy. Genetically encoded self-labeling tag proteins can be coupled to synthetic dyes inside living cells, resulting in brighter reporters than fluorescent proteins. Intracellular labeling using these techniques requires cell-permeable fluorescent ligands, however, limiting utility to a small number of classic fluorophores. Here we describe a simple structural modification that improves the brightness and photostability of dyes while preserving spectral properties and cell permeability. Inspired by molecular modeling, we replaced the N,N-dimethylamino substituents in tetramethylrhodamine with four-membered azetidine rings. This addition of two carbon atoms doubles the quantum efficiency and improves the photon yield of the dye in applications ranging from in vitro single-molecule measurements to super-resolution imaging. The novel substitution is generalizable, yielding a palette of chemical dyes with improved quantum efficiencies that spans the UV and visible range.
TL;DR: The findings are the first to demonstrate a link between a genetically defined subtype of cancer and its corresponding expression of immune checkpoints in the tumor microenvironment, and suggest that blockade of specific checkpoints may be selectively efficacious in the MSI subset of colorectal cancer.
Abstract: We examined the immune microenvironment of primary colorectal cancer using immunohistochemistry, laser capture microdissection/qRT-PCR, flow cytometry, and functional analysis of tumor-infiltrating lymphocytes. A subset of colorectal cancer displayed high infiltration with activated CD8+ cytotoxic T lymphocyte (CTL) as well as activated Th1 cells characterized by IFNγ production and the Th1 transcription factor TBET. Parallel analysis of tumor genotypes revealed that virtually all of the tumors with this active Th1/CTL microenvironment had defects in mismatch repair, as evidenced by microsatellite instability (MSI). Counterbalancing this active Th1/CTL microenvironment, MSI tumors selectively demonstrated highly upregulated expression of multiple immune checkpoints, including five—PD-1, PD-L1, CTLA-4, LAG-3, and IDO—currently being targeted clinically with inhibitors. These findings link tumor genotype with the immune microenvironment, and explain why MSI tumors are not naturally eliminated despite a hostile Th1/CTL microenvironment. They further suggest that blockade of specific checkpoints may be selectively efficacious in the MSI subset of colorectal cancer.
Significance: The findings reported in this article are the first to demonstrate a link between a genetically defined subtype of cancer and its corresponding expression of immune checkpoints in the tumor microenvironment. The mismatch repair–defective subset of colorectal cancer selectively upregulates at least five checkpoint molecules that are targets of inhibitors currently being clinically tested. Cancer Discov; 5(1); 43–51. ©2014 AACR.
See related commentary by Xiao and Freeman, [p. 16][1]
This article is highlighted in the In This Issue feature, [p. 1][2]
[1]: /lookup/volpage/5/16?iss=1
[2]: /lookup/volpage/5/1?iss=1
Harvard University1, Broad Institute2, Howard Hughes Medical Institute3, University College Dublin4, Emory University5, University of Copenhagen6, Trinity College, Dublin7, University of Adelaide8, Russian Academy of Sciences9, Complutense University of Madrid10, Rovira i Virgili University11, University of Valladolid12, Max Planck Society13, University of Tübingen14, Danube Private University15, University of Basel16, Hartwick College17, Pompeu Fabra University18
TL;DR: A genome-wide scan for selection using ancient DNA is reported, capitalizing on the largest ancient DNA data set yet assembled: 230 West Eurasians who lived between 6500 and 300 bc, including 163 with newly reported data.
Abstract: Ancient DNA makes it possible to observe natural selection directly by analysing samples from populations before, during and after adaptation events. Here we report a genome-wide scan for selection using ancient DNA, capitalizing on the largest ancient DNA data set yet assembled: 230 West Eurasians who lived between 6500 and 300 bc, including 163 with newly reported data. The new samples include, to our knowledge, the first genome-wide ancient DNA from Anatolian Neolithic farmers, whose genetic material we obtained by extracting from petrous bones, and who we show were members of the population that was the source of Europe's first farmers. We also report a transect of the steppe region in Samara between 5600 and 300 bc, which allows us to identify admixture into the steppe from at least two external sources. We detect selection at loci associated with diet, pigmentation and immunity, and two independent episodes of selection on height.
TL;DR: A browser for the first new human genome reference assembly in 4 years in December 2013, a watershed comparative genomics annotation (100-species multiple alignment and conservation), and a novel distribution mechanism for the browser are among the highlights of the past year.
Abstract: Launched in 2001 to showcase the draft human genome assembly, the UCSC Genome Browser database (http://genome.ucsc.edu) and associated tools continue to grow, providing a comprehensive resource of genome assemblies and annotations to scientists and students worldwide. Highlights of the past year include the release of a browser for the first new human genome reference assembly in 4 years in December 2013 (GRCh38, UCSC hg38), a watershed comparative genomics annotation (100-species multiple alignment and conservation) and a novel distribution mechanism for the browser (GBiB: Genome Browser in a Box). We created browsers for new species (Chinese hamster, elephant shark, minke whale), 'mined the web' for DNA sequences and expanded the browser display with stacked color graphs and region highlighting. As our user community increasingly adopts the UCSC track hub and assembly hub representations for sharing large-scale genomic annotation data sets and genome sequencing projects, our menu of public data hubs has tripled.
TL;DR: This Review highlights emerging mechanisms of acquired resistance to contemporary therapies targeting the AR pathway, which fall into the three broad categories of restored AR signalling, AR bypass signalling and complete AR independence.
Abstract: During the past 10 years, preclinical studies implicating sustained androgen receptor (AR) signalling as the primary driver of castration-resistant prostate cancer (CRPC) have led to the development of novel agents targeting the AR pathway that are now in widespread clinical use. These drugs prolong the survival of patients with late-stage prostate cancer but are not curative. In this Review, we highlight emerging mechanisms of acquired resistance to these contemporary therapies, which fall into the three broad categories of restored AR signalling, AR bypass signalling and complete AR independence. This diverse range of resistance mechanisms presents new challenges for long-term disease control, which may be addressable through early use of combination therapies guided by recent insights from genomic landscape studies of CRPC.
TL;DR: New metabolic checkpoints for T cell activity are uncovered and it is demonstrated that metabolic reprogramming of tumor-reactive T cells can enhance anti-tumor T cell responses, illuminating new forms of immunotherapy.
TL;DR: This Historical Commentary reflects on the scientific landscape of this decade-long transition between microbial opsin engineering and modular genetic methods for cell-type targeting, with the publication of thousands of discoveries and insights into the function of nervous systems and beyond.
Abstract: Over the past 10 years, the development and convergence of microbial opsin engineering, modular genetic methods for cell-type targeting and optical strategies for guiding light through tissue have enabled versatile optical control of defined cells in living systems, defining modern optogenetics. Despite widespread recognition of the importance of spatiotemporally precise causal control over cellular signaling, for nearly the first half (2005-2009) of this 10-year period, as optogenetics was being created, there were difficulties in implementation, few publications and limited biological findings. In contrast, the ensuing years have witnessed a substantial acceleration in the application domain, with the publication of thousands of discoveries and insights into the function of nervous systems and beyond. This Historical Commentary reflects on the scientific landscape of this decade-long transition.
TL;DR: It is demonstrated that micronucleus formation can indeed generate a spectrum of genomic rearrangements, some of which recapitulate all known features of chromothripsis.
Abstract: Genome sequencing has uncovered a new mutational phenomenon in cancer and congenital disorders called chromothripsis. Chromothripsis is characterized by extensive genomic rearrangements and an oscillating pattern of DNA copy number levels, all curiously restricted to one or a few chromosomes. The mechanism for chromothripsis is unknown, but we previously proposed that it could occur through the physical isolation of chromosomes in aberrant nuclear structures called micronuclei. Here, using a combination of live cell imaging and single-cell genome sequencing, we demonstrate that micronucleus formation can indeed generate a spectrum of genomic rearrangements, some of which recapitulate all known features of chromothripsis. These events are restricted to the mis-segregated chromosome and occur within one cell division. We demonstrate that the mechanism for chromothripsis can involve the fragmentation and subsequent reassembly of a single chromatid from a micronucleus. Collectively, these experiments establish a new mutational process of which chromothripsis is one extreme outcome.
TL;DR: These co-transcriptional silencing mechanisms form powerful RNA surveillance systems that detect and silence inappropriate transcription events, and provide a memory of these events via self-reinforcing epigenetic loops.
Abstract: Diverse classes of RNA, ranging from small to long non-coding RNAs, have emerged as key regulators of gene expression, genome stability and defence against foreign genetic elements. Small RNAs modify chromatin structure and silence transcription by guiding Argonaute-containing complexes to complementary nascent RNA scaffolds and then mediating the recruitment of histone and DNA methyltransferases. In addition, recent advances suggest that chromatin-associated long non-coding RNA scaffolds also recruit chromatin-modifying complexes independently of small RNAs. These co-transcriptional silencing mechanisms form powerful RNA surveillance systems that detect and silence inappropriate transcription events, and provide a memory of these events via self-reinforcing epigenetic loops.
Paris Descartes University1, Institut Gustave Roussy2, Mount Sinai Hospital3, University of Texas Southwestern Medical Center4, University of Kiel5, Thomas Jefferson University6, Seconda Università degli Studi di Napoli7, University of Toronto8, University of Massachusetts Medical School9, Louisiana State University10, Ghent University11, Flanders Institute for Biotechnology12, Cancer Research UK13, Queen Mary University of London14, Roswell Park Cancer Institute15, Karolinska Institutet16, University of Freiburg17, University of California, San Francisco18, Buck Institute for Research on Aging19, French Institute of Health and Medical Research20, Université Paris-Saclay21, University College London22, University of Rome Tor Vergata23, Northwestern University24, Memorial Sloan Kettering Cancer Center25, National Institutes of Health26, Technion – Israel Institute of Technology27, Johns Hopkins University28, University of Chieti-Pescara29, University of Ulm30, Genentech31, New York University32, Pennsylvania State University33, University of Salento34, Yale University35, Goethe University Frankfurt36, University of Burgundy37, Pasteur Institute38, University of Strasbourg39, University of Zurich40, University of Tokyo41, Technische Universität München42, University of Bern43, University of Michigan44, Medical Research Council45, University of South Australia46, University of Adelaide47, Medical University of South Carolina48, Howard Hughes Medical Institute49, University of Texas at Dallas50, St. John's University51, University of Oviedo52, University of Graz53, Istituto Superiore di Sanità54, Katholieke Universiteit Leuven55, Trinity College, Dublin56, University of Geneva57, University of Amsterdam58, Stony Brook University59, University of Washington60, University of Ferrara61, Royal College of Surgeons in Ireland62, La Trobe University63, University of Buenos Aires64, University of Virginia65, University of Padua66, University of Lisbon67, University of Cambridge68, University of Würzburg69, Soochow University (Suzhou)70, Columbia University71, University of Glasgow72, University of Crete73, Foundation for Research & Technology – Hellas74, Innsbruck Medical University75, Carlos III Health Institute76, Rutgers University77, University of Minnesota78, Harvard University79, City University of New York80, Moscow State University81
TL;DR: The Nomenclature Committee on Cell Death formulates a set of recommendations to help scientists and researchers to discriminate between essential and accessory aspects of cell death.
Abstract: Cells exposed to extreme physicochemical or mechanical stimuli die in an uncontrollable manner, as a result of their immediate structural breakdown. Such an unavoidable variant of cellular demise is generally referred to as ‘accidental cell death’ (ACD). In most settings, however, cell death is initiated by a genetically encoded apparatus, correlating with the fact that its course can be altered by pharmacologic or genetic interventions. ‘Regulated cell death’ (RCD) can occur as part of physiologic programs or can be activated once adaptive responses to perturbations of the extracellular or intracellular microenvironment fail. The biochemical phenomena that accompany RCD may be harnessed to classify it into a few subtypes, which often (but not always) exhibit stereotyped morphologic features. Nonetheless, efficiently inhibiting the processes that are commonly thought to cause RCD, such as the activation of executioner caspases in the course of apoptosis, does not exert true cytoprotective effects in the mammalian system, but simply alters the kinetics of cellular demise as it shifts its morphologic and biochemical correlates. Conversely, bona fide cytoprotection can be achieved by inhibiting the transduction of lethal signals in the early phases of the process, when adaptive responses are still operational. Thus, the mechanisms that truly execute RCD may be less understood, less inhibitable and perhaps more homogeneous than previously thought. Here, the Nomenclature Committee on Cell Death formulates a set of recommendations to help scientists and researchers to discriminate between essential and accessory aspects of cell death.
Icahn School of Medicine at Mount Sinai1, University of Zurich2, Genomics Institute of the Novartis Research Foundation3, Discovery Institute4, Oregon State University5, University of Massachusetts Medical School6, Brigham and Women's Hospital7, Howard Hughes Medical Institute8, University of Texas Southwestern Medical Center9, Columbia University10, Harvard University11, Max Planck Society12, University of California, San Francisco13, Paul Ehrlich Institute14
TL;DR: A meta-analysis of data from eight published RNAi screens and integrated with three protein interaction datasets revealed a functionally validated biochemical landscape of the influenza-host interface, which illuminates a viral-host network of high-confidence human proteins that are essential for influenza A virus replication.
TL;DR: The method for single-cell analysis reveals aspects of epigenetic heterogeneity not captured by transcriptional analysis alone, and identifies a spectrum of subpopulations defined by differences in chromatin signatures of pluripotency and differentiation priming.
Abstract: Chromatin profiling provides a versatile means to investigate functional genomic elements and their regulation. However, current methods yield ensemble profiles that are insensitive to cell-to-cell variation. Here we combine microfluidics, DNA barcoding and sequencing to collect chromatin data at single-cell resolution. We demonstrate the utility of the technology by assaying thousands of individual cells and using the data to deconvolute a mixture of ES cells, fibroblasts and hematopoietic progenitors into high-quality chromatin state maps for each cell type. The data from each single cell are sparse, comprising on the order of 1,000 unique reads. However, by assaying thousands of ES cells, we identify a spectrum of subpopulations defined by differences in chromatin signatures of pluripotency and differentiation priming. We corroborate these findings by comparison to orthogonal single-cell gene expression data. Our method for single-cell analysis reveals aspects of epigenetic heterogeneity not captured by transcriptional analysis alone.