Showing papers in "Nature Reviews Genetics in 2016"
TL;DR: These and other strategies are providing researchers and clinicians a variety of tools to probe genomes in greater depth, leading to an enhanced understanding of how genome sequence variants underlie phenotype and disease.
Abstract: Since the completion of the human genome project in 2003, extraordinary progress has been made in genome sequencing technologies, which has led to a decreased cost per megabase and an increase in the number and diversity of sequenced genomes. An astonishing complexity of genome architecture has been revealed, bringing these sequencing technologies to even greater advancements. Some approaches maximize the number of bases sequenced in the least amount of time, generating a wealth of data that can be used to understand increasingly complex phenotypes. Alternatively, other approaches now aim to sequence longer contiguous pieces of DNA, which are essential for resolving structurally complex regions. These and other strategies are providing researchers and clinicians a variety of tools to probe genomes in greater depth, leading to an enhanced understanding of how genome sequence variants underlie phenotype and disease.
3,096 citations
TL;DR: This Review describes special events in the lifetimes of lncRNAs — before, during and after transcription — and discusses how these events ultimately shape the unique characteristics and functional roles of lNCRNAs.
Abstract: Long non-coding RNAs (lncRNAs) are a diverse class of RNAs that engage in numerous biological processes across every branch of life. Although initially discovered as mRNA-like transcripts that do not encode proteins, recent studies have revealed features of lncRNAs that further distinguish them from mRNAs. In this Review, we describe special events in the lifetimes of lncRNAs - before, during and after transcription - and discuss how these events ultimately shape the unique characteristics and functional roles of lncRNAs.
2,568 citations
TL;DR: A personal perspective on the development of epigenetics, from its historical origins to what is defined as 'the modern era of epigenetic research', is provided.
Abstract: Over the past 20 years, breakthrough discoveries of chromatin-modifying enzymes and associated mechanisms that alter chromatin in response to physiological or pathological signals have transformed our knowledge of epigenetics from a collection of curious biological phenomena to a functionally dissected research field. Here, we provide a personal perspective on the development of epigenetics, from its historical origins to what we define as 'the modern era of epigenetic research'. We primarily highlight key molecular mechanisms of and conceptual advances in epigenetic control that have changed our understanding of normal and perturbed development.
1,764 citations
TL;DR: The evidence for and against the ceRNA hypothesis are critically evaluated to assess the impact of endogenous miRNA-sponge interactions and to propose an alternative function for messenger RNAs.
Abstract: The competitive endogenous RNA (ceRNA) hypothesis proposes that transcripts with shared microRNA (miRNA) binding sites compete for post-transcriptional control. This hypothesis has gained substantial attention as a unifying function for long non-coding RNAs, pseudogene transcripts and circular RNAs, as well as an alternative function for messenger RNAs. Empirical evidence supporting the hypothesis is accumulating but not without attracting scepticism. Recent studies that model transcriptome-wide binding-site abundance suggest that physiological changes in expression of most individual transcripts will not compromise miRNA activity. In this Review, we critically evaluate the evidence for and against the ceRNA hypothesis to assess the impact of endogenous miRNA-sponge interactions.
1,463 citations
TL;DR: This Review provides a comprehensive discussion of RADseq methods to aid researchers in choosing among the many different approaches and avoiding erroneous scientific conclusions from RADseq data, a problem that has plagued other genetic marker types in the past.
Abstract: High-throughput techniques based on restriction site-associated DNA sequencing (RADseq) are enabling the low-cost discovery and genotyping of thousands of genetic markers for any species, including non-model organisms, which is revolutionizing ecological, evolutionary and conservation genetics. Technical differences among these methods lead to important considerations for all steps of genomics studies, from the specific scientific questions that can be addressed, and the costs of library preparation and sequencing, to the types of bias and error inherent in the resulting data. In this Review, we provide a comprehensive discussion of RADseq methods to aid researchers in choosing among the many different approaches and avoiding erroneous scientific conclusions from RADseq data, a problem that has plagued other genetic marker types in the past.
1,102 citations
TL;DR: An overview of the current state of the field of single-cell genome sequencing is provided, focusing on the technical challenges of making measurements that start from a single molecule of DNA, and how some of these recent methodological advancements have enabled the discovery of unexpected new biology.
Abstract: Single-cell genome sequencing can provide detailed insights into the composition of single genomes that are not readily apparent when studying bulk cell populations. This Review discusses the considerable technical challenges of amplifying and interrogating genomes from single cells, emerging innovative solutions and various applications in microbiology and human disease, in particular in cancer.
1,061 citations
TL;DR: As epigenetic drugs target the epigenome as a whole, these true 'genomic medicines' lessen the need for precision approaches to individualized therapies.
Abstract: Next-generation sequencing has revealed that more than 50% of human cancers harbour mutations in enzymes that are involved in chromatin organization. Tumour cells not only are activated by genetic and epigenetic alterations, but also routinely use epigenetic processes to ensure their escape from chemotherapy and host immune surveillance. Hence, a growing emphasis of recent drug discovery efforts has been on targeting the epigenome, including DNA methylation and histone modifications, with several new drugs being tested and some already approved by the US Food and Drug Administration (FDA). The future will see the increasing success of combining epigenetic drugs with other therapies. As epigenetic drugs target the epigenome as a whole, these true 'genomic medicines' lessen the need for precision approaches to individualized therapies.
837 citations
TL;DR: An overview of RNA splicing mechanisms is provided followed by a discussion of disease-associated errors, with an emphasis on recently described mutations that have provided new insights into splicing regulation.
Abstract: Complex and intricate RNA splicing mechanisms are crucial for gene regulation and for maximizing proteomic diversity. This Review discusses how alterations to splicing mechanisms — such as mutations in pre-mRNAs, or mutations and dysregulation of core spliceosome proteins and other RNA-binding proteins — results in diverse molecular consequences and various diseases. Opportunities for therapeutic correction of these defects are also explored.
824 citations
TL;DR: The insights into chromatin architecture that have been gained through recent technological developments in quantitative biology, genomics and cell and molecular biology approaches are discussed and how these new concepts have been used to address important biological questions in development and disease are explained.
Abstract: Understanding how chromatin is organized within the nucleus and how this 3D architecture influences gene regulation, cell fate decisions and evolution are major questions in cell biology. Despite spectacular progress in this field, we still know remarkably little about the mechanisms underlying chromatin structure and how it can be established, reset and maintained. In this Review, we discuss the insights into chromatin architecture that have been gained through recent technological developments in quantitative biology, genomics and cell and molecular biology approaches and explain how these new concepts have been used to address important biological questions in development and disease.
810 citations
TL;DR: This work suggests a framework for cancer epigenetics involving three types of genes: 'epigenetic mediators', corresponding to the tumour progenitor genes suggested earlier; 'Epigenetic modifiers' of the mediators, which are frequently mutated in cancer; and 'epigetic modulators' upstream of the modifiers, which is responsive to changes in the cellular environment and often linked to the nuclear architecture.
Abstract: This year is the tenth anniversary of the publication in this journal of a model suggesting the existence of 'tumour progenitor genes'. These genes are epigenetically disrupted at the earliest stages of malignancies, even before mutations, and thus cause altered differentiation throughout tumour evolution. The past decade of discovery in cancer epigenetics has revealed a number of similarities between cancer genes and stem cell reprogramming genes, widespread mutations in epigenetic regulators, and the part played by chromatin structure in cellular plasticity in both development and cancer. In the light of these discoveries, we suggest here a framework for cancer epigenetics involving three types of genes: 'epigenetic mediators', corresponding to the tumour progenitor genes suggested earlier; 'epigenetic modifiers' of the mediators, which are frequently mutated in cancer; and 'epigenetic modulators' upstream of the modifiers, which are responsive to changes in the cellular environment and often linked to the nuclear architecture. We suggest that this classification is helpful in framing new diagnostic and therapeutic approaches to cancer.
666 citations
TL;DR: This work concludes that the drift-barrier hypothesis is consistent with comparative measures of mutation rates, provides a simple explanation for the existence of error-prone polymerases and yields a formal counter-argument to the view that selection fine-tunes gene-specific mutation rates.
Abstract: Mutation is the source of genetic diversity on which natural selection acts, therefore understanding the rates of mutations is crucial for understanding evolutionary trajectories. In this Opinion article, the authors discuss how emerging experimental mutation-rate data from genome-wide sequencing studies, combined with population-genetic theory, can provide unifying explanations for the diversity in mutation rates between species and across genomic locations.
TL;DR: A deeper understanding of disease will be realized that will allow its targeting with much greater therapeutic precision, and global sharing of more accurate genotypic and phenotypic data will accelerate the determination of causality for novel genes or variants.
Abstract: Precision medicine is a strategy for tailoring clinical decision making to the underlying genetic causes of disease. This Review describes how, despite the straightforward overall principles of precision medicine, adopting it responsibly into clinical practice will require many technical and conceptual hurdles to be overcome. Such challenges include optimized sequencing strategies, clinically focused bioinformatics pipelines and reliable metrics for the disease causality of genetic variants.
TL;DR: Research progress in the field of enhancer functions and mechanisms is reviewed and several important, unresolved questions regarding the roles and mechanisms of enhancers in gene regulation are discussed.
Abstract: The observation that many, if not all, functional enhancers generate non-coding enhancer RNAs (eRNAs) has raised critical questions regarding the potential biological roles of the enhancer transcription process and, indeed, of eRNAs. This article reviews fundamental insights into the inter-regulation of enhancers and promoters and discusses unresolved questions regarding the functional role of enhancers as transcription units in genome regulation.
TL;DR: The insights obtained from recent studies on the role of genetics in ID and its impact on diagnosis, prognosis and therapy are highlighted and the future directions of genetics research for ID and related neurodevelopmental disorders are discussed.
Abstract: Genetic factors play a major part in intellectual disability (ID), but genetic studies have been complicated for a long time by the extreme clinical and genetic heterogeneity. Recently, progress has been made using different next-generation sequencing approaches in combination with new functional readout systems. This approach has provided novel insights into the biological pathways underlying ID, improved the diagnostic process and offered new targets for therapy. In this Review, we highlight the insights obtained from recent studies on the role of genetics in ID and its impact on diagnosis, prognosis and therapy. We also discuss the future directions of genetics research for ID and related neurodevelopmental disorders.
TL;DR: This Review provides a summary of the methodologies used for building, evaluating and applying risk prediction models that include information from genetic testing and environmental risk factors.
Abstract: Knowledge of genetics and its implications for human health is rapidly evolving in accordance with recent events, such as discoveries of large numbers of disease susceptibility loci from genome-wide association studies, the US Supreme Court ruling of the non-patentability of human genes, and the development of a regulatory framework for commercial genetic tests. In anticipation of the increasing relevance of genetic testing for the assessment of disease risks, this Review provides a summary of the methodologies used for building, evaluating and applying risk prediction models that include information from genetic testing and environmental risk factors. Potential applications of models for primary and secondary disease prevention are illustrated through several case studies, and future challenges and opportunities are discussed.
TL;DR: Advances in experimental and computational approaches are revealing not just cancer pathways controlled by single miRNAAs but also intermeshed regulatory networks controlled by multiple miRNAs, which often engage in reciprocal feedback interactions with the targets that they regulate.
Abstract: MicroRNAs (miRNAs) participate in most aspects of cellular differentiation and homeostasis, and consequently have roles in many pathologies, including cancer These small non-coding RNAs exert their effects in the context of complex regulatory networks, often made all the more extensive by the inclusion of transcription factors as their direct targets In recent years, the increased availability of gene expression data and the development of methodologies that profile miRNA targets en masse have fuelled our understanding of miRNA functions, and of the sources and consequences of miRNA dysregulation Advances in experimental and computational approaches are revealing not just cancer pathways controlled by single miRNAs but also intermeshed regulatory networks controlled by multiple miRNAs, which often engage in reciprocal feedback interactions with the targets that they regulate
TL;DR: These questions are addressed, and insights are discussed from genomic studies of gene loss in populations and their relevance in evolutionary biology and biomedicine.
Abstract: The recent increase in genomic data is revealing an unexpected perspective of gene loss as a pervasive source of genetic variation that can cause adaptive phenotypic diversity. This novel perspective of gene loss is raising new fundamental questions. How relevant has gene loss been in the divergence of phyla? How do genes change from being essential to dispensable and finally to being lost? Is gene loss mostly neutral, or can it be an effective way of adaptation? These questions are addressed, and insights are discussed from genomic studies of gene loss in populations and their relevance in evolutionary biology and biomedicine.
Heidelberg University1, University of Cambridge2, Santa Fe Institute3, Albert Einstein College of Medicine4, Howard Hughes Medical Institute5, Smithsonian Institution6, Cincinnati Children's Hospital Medical Center7, University of Vienna8, Max Planck Society9, Wayne State University10, Yale University11
TL;DR: An evolutionary definition of a cell type is proposed that allows cell types to be delineated and compared within and between species, and the distinction between developmental and evolutionary lineages is discussed.
Abstract: Cell types are the basic building blocks of multicellular organisms and are extensively diversified in animals. Despite recent advances in characterizing cell types, classification schemes remain ambiguous. We propose an evolutionary definition of a cell type that allows cell types to be delineated and compared within and between species. Key to cell type identity are evolutionary changes in the 'core regulatory complex' (CoRC) of transcription factors, that make emergent sister cell types distinct, enable their independent evolution and regulate cell type-specific traits termed apomeres. We discuss the distinction between developmental and evolutionary lineages, and present a roadmap for future research.
TL;DR: It is the diversity of RNA species detected through RNA-seq that holds new promise for the multi-faceted clinical applicability of RNA-based measures, including the potential of extracellular RNAs as non-invasive diagnostic indicators of disease.
Abstract: With the emergence of RNA sequencing (RNA-seq) technologies, RNA-based biomolecules hold expanded promise for their diagnostic, prognostic and therapeutic applicability in various diseases, including cancers and infectious diseases. Detection of gene fusions and differential expression of known disease-causing transcripts by RNA-seq represent some of the most immediate opportunities. However, it is the diversity of RNA species detected through RNA-seq that holds new promise for the multi-faceted clinical applicability of RNA-based measures, including the potential of extracellular RNAs as non-invasive diagnostic indicators of disease. Ongoing efforts towards the establishment of benchmark standards, assay optimization for clinical conditions and demonstration of assay reproducibility are required to expand the clinical utility of RNA-seq.
TL;DR: This work reviews sources of experimental and bioinformatic biases that complicate the accurate discovery of circRNAs and discusses statistical approaches to address these biases.
Abstract: The pervasive expression of circular RNAs (circRNAs) is a recently discovered feature of gene expression in highly diverged eukaryotes. Numerous algorithms that are used to detect genome-wide circRNA expression from RNA sequencing (RNA-seq) data have been developed in the past few years, but there is little overlap in their predictions and no clear gold-standard method to assess the accuracy of these algorithms. We review sources of experimental and bioinformatic biases that complicate the accurate discovery of circRNAs and discuss statistical approaches to address these biases. We conclude with a discussion of the current experimental progress on the topic.
TL;DR: These reports showcase the influence of repeat sequences on genomic stability and structural variant complexity and also highlight the tremendous plasticity and dynamic nature of the genome in evolution, health and disease susceptibility.
Abstract: With the recent burst of technological developments in genomics, and the clinical implementation of genome-wide assays, our understanding of the molecular basis of genomic disorders, specifically the contribution of structural variation to disease burden, is evolving quickly. Ongoing studies have revealed a ubiquitous role for genome architecture in the formation of structural variants at a given locus, both in DNA recombination-based processes and in replication-based processes. These reports showcase the influence of repeat sequences on genomic stability and structural variant complexity and also highlight the tremendous plasticity and dynamic nature of our genome in evolution, health and disease susceptibility.
TL;DR: Comparative population genomics is on its way to providing a solution to 'Lewontin's paradox' — the discrepancy between the many orders of magnitude of variation in population size and the much narrower distribution of diversity levels.
Abstract: The degree of genetic diversity differs greatly among species and across genomic loci within genomes. The wide ranges in genetic diversity have important implications, including for evolution, conservation and management of wild and domesticated species. In this Review, the authors discuss how genome-scale sequencing strategies are providing insight into the varied determinants of genetic variation both among species and across genomic regions.
TL;DR: Evidence is emerging to suggest that transcription factors lacking a MBD can also interact with methylated DNA, and the identification of these proteins and the elucidation of their characteristics and the biological consequences are important stepping stones towards a mechanistic understanding of methylation-mediated biological processes.
Abstract: Recent technological advances have made it possible to decode DNA methylomes at single-base-pair resolution under various physiological conditions. Many aberrant or differentially methylated sites have been discovered, but the mechanisms by which changes in DNA methylation lead to observed phenotypes, such as cancer, remain elusive. The classical view of methylation-mediated protein-DNA interactions is that only proteins with a methyl-CpG binding domain (MBD) can interact with methylated DNA. However, evidence is emerging to suggest that transcription factors lacking a MBD can also interact with methylated DNA. The identification of these proteins and the elucidation of their characteristics and the biological consequences of methylation-dependent transcription factor-DNA interactions are important stepping stones towards a mechanistic understanding of methylation-mediated biological processes, which have crucial implications for human development and disease.
TL;DR: The current understanding of non-coding variants in cancer is reviewed, including the great diversity of the mutation types — from single nucleotide variants to large genomic rearrangements — and the wide range of mechanisms by which they affect gene expression to promote tumorigenesis.
Abstract: Genomic analyses of cancer genomes have largely focused on mutations in protein-coding regions, but the functional importance of alterations to non-coding regions is becoming increasingly appreciated through whole-genome sequencing. This Review discusses our current understanding of non-coding sequence variants in cancer — both somatic mutations and germline variants, and their interplay — including their identification, computational and experimental evidence for functional impact, and their diverse mechanisms of action for dysregulating coding genes and non-coding RNAs.
TL;DR: The lessons learned so far from genome-wide mapping and comparisons of lncRNAs across different species are reviewed and how comparative analyses can help to understand lncRNA function are discussed.
Abstract: Long non-coding RNAs (lncRNAs) have emerged in recent years as major players in a multitude of pathways across species, but it remains challenging to understand which of them are important and how their functions are performed. Comparative sequence analysis has been instrumental for studying proteins and small RNAs, but the rapid evolution of lncRNAs poses new challenges that demand new approaches. Here, I review the lessons learned so far from genome-wide mapping and comparisons of lncRNAs across different species. I also discuss how comparative analyses can help us to understand lncRNA function and provide practical considerations for examining functional conservation of lncRNA genes.
TL;DR: The different types of engineered gene drives and their potential applications are discussed, as well as current policies regarding the safety and regulation of gene drives for the manipulation of wild populations.
Abstract: Engineered gene drives - the process of stimulating the biased inheritance of specific genes - have the potential to enable the spread of desirable genes throughout wild populations or to suppress harmful species, and may be particularly useful for the control of vector-borne diseases such as malaria. Although several types of selfish genetic elements exist in nature, few have been successfully engineered in the laboratory thus far. With the discovery of RNA-guided CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-CRISPR-associated 9) nucleases, which can be utilized to create, streamline and improve synthetic gene drives, this is rapidly changing. Here, we discuss the different types of engineered gene drives and their potential applications, as well as current policies regarding the safety and regulation of gene drives for the manipulation of wild populations.
TL;DR: The state-of-the-art understanding of target DNA recognition and cleavage by CRISPR–Cas9 nucleases is outlined, methods to determine and improve their specificities, and key considerations for how to evaluate and reduce off-target effects for research and therapeutic applications are outlined.
Abstract: CRISPR-Cas9 RNA-guided nucleases are a transformative technology for biology, genetics and medicine owing to the simplicity with which they can be programmed to cleave specific DNA target sites in living cells and organisms. However, to translate these powerful molecular tools into safe, effective clinical applications, it is of crucial importance to carefully define and improve their genome-wide specificities. Here, we outline our state-of-the-art understanding of target DNA recognition and cleavage by CRISPR-Cas9 nucleases, methods to determine and improve their specificities, and key considerations for how to evaluate and reduce off-target effects for research and therapeutic applications.
TL;DR: Insight is reviewed into the possible mechanisms by which sperm become acquisitive following environmental–somatic–germline interactions, and how they transmit paternally acquired phenotypes by shaping early embryonic development.
Abstract: Once deemed heretical, emerging evidence now supports the notion that the inheritance of acquired characteristics can occur through ancestral exposures or experiences and that certain paternally acquired traits can be 'memorized' in the sperm as epigenetic information. The search for epigenetic factors in mammalian sperm that transmit acquired phenotypes has recently focused on RNAs and, more recently, RNA modifications. Here, we review insights that have been gained from studying sperm RNAs and RNA modifications, and their roles in influencing offspring phenotypes. We discuss the possible mechanisms by which sperm become acquisitive following environmental-somatic-germline interactions, and how they transmit paternally acquired phenotypes by shaping early embryonic development.
TL;DR: Here, focusing strictly on the fate decision events, it is suggested that fate transitions occur in a discontinuous, stochastic manner whereby signals modulate the probability of the transition events.
Abstract: Formal representations of Waddington's epigenetic landscape represent cell fate decisions as smooth, continuous events in which cells follow predetermined trajectories. Here, the authors provide an alternative interpretation and posit that fate decisions are discontinuous, stochastic events within cell lineages. Waddington's epigenetic landscape is an abstract metaphor frequently used to represent the relationship between gene activity and cell fates during development. Over the past few years, it has become a useful framework for interpreting results from single-cell transcriptomics experiments. It has led to the proposal that, during fate transitions, cells experience smooth, continuous progressions of global transcriptional activity, which can be captured by (pseudo)temporal dynamics. Here, focusing strictly on the fate decision events, we suggest an alternative view: that fate transitions occur in a discontinuous, stochastic manner whereby signals modulate the probability of the transition events.
TL;DR: The overall developmental dynamics of human and mouse germline cells appear to be similar, but there are crucial mechanistic differences in PGC specification, reflecting divergence in the regulation of pluripotency and early development.
Abstract: Primordial germ cells (PGCs), the precursors of sperm and eggs, are established in perigastrulation-stage embryos in mammals. Signals from extra-embryonic tissues induce a unique gene regulatory network in germline-competent cells for PGC specification. This network also initiates comprehensive epigenome resetting, including global DNA demethylation and chromatin reorganization. Mouse germline development has been studied extensively, but the extent to which such knowledge applies to humans was unclear. Here, we review the latest advances in human PGC specification and epigenetic reprogramming. The overall developmental dynamics of human and mouse germline cells appear to be similar, but there are crucial mechanistic differences in PGC specification, reflecting divergence in the regulation of pluripotency and early development.