Showing papers in "Nature Reviews Genetics in 2017"
TL;DR: Genome-wide analyses of the clock transcriptional feedback loop have revealed a global circadian regulation of processes such as transcription factor occupancy, RNA polymerase II recruitment and initiation, nascent transcription, and chromatin remodelling.
Abstract: Circadian clocks are endogenous oscillators that control 24-hour physiological and behavioural processes in organisms. These cell-autonomous clocks are composed of a transcription-translation-based autoregulatory feedback loop. With the development of next-generation sequencing approaches, biochemical and genomic insights into circadian function have recently come into focus. Genome-wide analyses of the clock transcriptional feedback loop have revealed a global circadian regulation of processes such as transcription factor occupancy, RNA polymerase II recruitment and initiation, nascent transcription, and chromatin remodelling. The genomic targets of circadian clocks are pervasive and are intimately linked to the regulation of metabolism, cell growth and physiology.
1,538 citations
TL;DR: How, once polyploidy has been established, the unique retention profile of duplicated genes following whole-genome duplication might explain key longer-term evolutionary transitions and a general increase in biological complexity is discussed.
Abstract: Polyploidy, or the duplication of entire genomes, has been observed in prokaryotic and eukaryotic organisms, and in somatic and germ cells. The consequences of polyploidization are complex and variable, and they differ greatly between systems (clonal or non-clonal) and species, but the process has often been considered to be an evolutionary 'dead end'. Here, we review the accumulating evidence that correlates polyploidization with environmental change or stress, and that has led to an increased recognition of its short-term adaptive potential. In addition, we discuss how, once polyploidy has been established, the unique retention profile of duplicated genes following whole-genome duplication might explain key longer-term evolutionary transitions and a general increase in biological complexity.
1,031 citations
TL;DR: Recent advances in biochemical and structural studies have revealed mechanistic insights into how TET and TDG mediate active DNA demethylation and many regulatory mechanisms of this process have been identified.
Abstract: A key mode of regulating DNA methylation is through active demethylation driven by TET-mediated oxidation of 5-methylcytosine (5mC). This Review discusses our latest understanding of the mechanisms and regulation of active DNA demethylation, and the roles of active demethylation (and the oxidized 5mC intermediates) in gene regulation, genome stability, development and disease.
1,012 citations
TL;DR: Recent findings supporting the long-standing hypothesis that the waves of TE invasions endured by organisms for eons have catalysed the evolution of gene-regulatory networks are reviewed.
Abstract: Transposable elements (TEs) are widely known for their deleterious consequences of selfish propagation and mutagenesis. However, as described in this Review, TEs also provide hosts with rich, beneficial gene-regulatory machinery in the form of regulatory DNA elements and TE-derived gene products. The authors highlight the diverse regulatory contributions of TEs to organismal physiology and pathology, provide a framework for responsibly assigning functional roles to TEs and offer visions for the future.
964 citations
TL;DR: All these approaches to genetic analysis using networks are variations of a unifying mathematical machinery — network propagation — suggesting that it is a powerful data transformation method of broad utility in genetic research.
Abstract: Biological networks are powerful resources for the discovery of genes and genetic modules that drive disease. Fundamental to network analysis is the concept that genes underlying the same phenotype tend to interact; this principle can be used to combine and to amplify signals from individual genes. Recently, numerous bioinformatic techniques have been proposed for genetic analysis using networks, based on random walks, information diffusion and electrical resistance. These approaches have been applied successfully to identify disease genes, genetic modules and drug targets. In fact, all these approaches are variations of a unifying mathematical machinery - network propagation - suggesting that it is a powerful data transformation method of broad utility in genetic research.
502 citations
TL;DR: The major developments in this field are outlined through a structured discussion of detection principles, advantages and drawbacks of new high-throughput methods are laid out, and conventional biophysical identification of modifications as meaningful ways for validation are presented.
Abstract: RNA modifications are emerging players in the field of post-transcriptional regulation of gene expression, and are attracting a comparable degree of research interest to DNA and histone modifications in the field of epigenetics. We now know of more than 150 RNA modifications and the true potential of a few of these is currently emerging as the consequence of a leap in detection technology, principally associated with high-throughput sequencing. This Review outlines the major developments in this field through a structured discussion of detection principles, lays out advantages and drawbacks of new high-throughput methods and presents conventional biophysical identification of modifications as meaningful ways for validation.
448 citations
TL;DR: Genetic testing could enable precision medicine approaches by identifying subgroups of patients at increased risk of coronary artery disease or those with a specific driving pathophysiology in whom a therapeutic or preventive approach would be most useful.
Abstract: Coronary artery disease is the leading global cause of mortality. Long recognized to be heritable, recent advances have started to unravel the genetic architecture of the disease. Common variant association studies have linked approximately 60 genetic loci to coronary risk. Large-scale gene sequencing efforts and functional studies have facilitated a better understanding of causal risk factors, elucidated underlying biology and informed the development of new therapeutics. Moving forwards, genetic testing could enable precision medicine approaches by identifying subgroups of patients at increased risk of coronary artery disease or those with a specific driving pathophysiology in whom a therapeutic or preventive approach would be most useful.
418 citations
TL;DR: Advances in next-generation sequencing technologies are enabling the identification of hundreds of tumour-specific mutations and alterations in gene expression that could be targeted by a synthetic lethality approach.
Abstract: A synthetic lethal interaction occurs between two genes when the perturbation of either gene alone is viable but the perturbation of both genes simultaneously results in the loss of viability. Key to exploiting synthetic lethality in cancer treatment are the identification and the mechanistic characterization of robust synthetic lethal genetic interactions. Advances in next-generation sequencing technologies are enabling the identification of hundreds of tumour-specific mutations and alterations in gene expression that could be targeted by a synthetic lethality approach. The translation of synthetic lethality to therapy will be assisted by the synthesis of genetic interaction data from model organisms, tumour genomes and human cell lines.
413 citations
TL;DR: Recent progress on statistical methods that leverage summary association data to gain insights into the genetic basis of complex traits and diseases are reviewed.
Abstract: During the past decade, genome-wide association studies (GWAS) have been used to successfully identify tens of thousands of genetic variants associated with complex traits and diseases. These studies have produced extensive repositories of genetic variation and trait measurements across large numbers of individuals, providing tremendous opportunities for further analyses. However, privacy concerns and other logistical considerations often limit access to individual-level genetic data, motivating the development of methods that analyse summary association statistics. Here, we review recent progress on statistical methods that leverage summary association data to gain insights into the genetic basis of complex traits and diseases.
387 citations
TL;DR: New advances in genome-wide technologies have paved the way towards an integrative view of epigenome dynamics during cell state transitions, and recent findings in embryonic stem cells highlight how the interplay between different epigenetic layers reshapes the transcriptional landscape.
Abstract: Chromatin, the template for epigenetic regulation, is a highly dynamic entity that is constantly reshaped during early development and differentiation. Epigenetic modification of chromatin provides the necessary plasticity for cells to respond to environmental and positional cues, and enables the maintenance of acquired information without changing the DNA sequence. The mechanisms involve, among others, chemical modifications of chromatin, changes in chromatin constituents and reconfiguration of chromatin interactions and 3D structure. New advances in genome-wide technologies have paved the way towards an integrative view of epigenome dynamics during cell state transitions, and recent findings in embryonic stem cells highlight how the interplay between different epigenetic layers reshapes the transcriptional landscape.
373 citations
TL;DR: This Review explores methodological trends in speciation genomic studies, highlights the difficulty in separating processes related to speciation from those emerging from genome-wide properties that are not related to reproductive isolation, and provides a set of suggestions for future work in this area.
Abstract: As populations diverge, genetic differences accumulate across the genome. Spurred by rapid developments in sequencing technology, genome-wide population surveys of natural populations promise insights into the evolutionary processes and the genetic basis underlying speciation. Although genomic regions of elevated differentiation are the focus of searches for 'speciation genes', there is an increasing realization that such genomic signatures can also arise by alternative processes that are not related to population divergence, such as linked selection. In this Review, we explore methodological trends in speciation genomic studies, highlight the difficulty in separating processes related to speciation from those emerging from genome-wide properties that are not related to reproductive isolation, and provide a set of suggestions for future work in this area.
TL;DR: Findings indicate that aetiological heterogeneity, variable penetrance and genetic pleiotropy are pervasive characteristics of autism genetics.
Abstract: Genetic studies have revealed the involvement of hundreds of gene variants in autism. Their risk effects are highly variable, and they are frequently related to other conditions besides autism. However, many different variants converge on common biological pathways. These findings indicate that aetiological heterogeneity, variable penetrance and genetic pleiotropy are pervasive characteristics of autism genetics. Although this advancing insight should improve clinical care, at present there is a substantial discrepancy between research knowledge and its clinical application. In this Review, we discuss the current challenges and opportunities for the translation of autism genetics knowledge into clinical practice.
TL;DR: A number of recent findings support the hypothesis that certain host genetic variants predispose an individual towards microbiome dysbiosis, a condition in which the normal microbiome population structure is disturbed.
Abstract: Taxonomic and functional changes to the composition of the gut microbiome have been implicated in multiple human diseases. Recent microbiome genome-wide association studies reveal that variants in many human genes involved in immunity and gut architecture are associated with an altered composition of the gut microbiome. Although many factors can affect the microbial organisms residing in the gut, a number of recent findings support the hypothesis that certain host genetic variants predispose an individual towards microbiome dysbiosis. This condition, in which the normal microbiome population structure is disturbed, is a key feature in disorders of metabolism and immunity.
TL;DR: The unusual plasticity in the bipotential system of sex determination and some of the diverse mechanisms that have evolved to control this critical developmental decision are considered, including strong genetic pathways, environmental influences and epigenetic regulation.
Abstract: The discovery of the Sry gene in 1990 triggered a revolution in our understanding of sex determination. More recently, advances in non-model organisms have been fuelled by the rapid evolution of affordable genome and transcriptome technologies. This Review considers the unusual plasticity in the bipotential system of sex determination and some of the diverse mechanisms that have evolved to control this critical developmental decision, including strong genetic pathways, environmental influences and epigenetic regulation. Ideas emerging from model and non-model organisms that suggest that sex determination operates as an antagonistic network with the emergent property of bistability are discussed.
TL;DR: A review of microfluidic methodologies for characterization of the genomes, epigenomes, transcriptomes and proteomes of single cells is presented in this article, with a primary focus on valve-, droplet-and nanowell-based platforms.
Abstract: As the genetic and phenotypic heterogeneities among cells become more appreciated, there is increasing demand for technologies that facilitate high-throughput and high-efficiency single-cell 'omic' analyses in miniaturized and automated formats. This Review discusses the diverse microfluidic methodologies — with a primary focus on valve-, droplet- and nanowell-based platforms — for characterization of the genomes, epigenomes, transcriptomes and proteomes of single cells, and addresses technical considerations and future opportunities.
TL;DR: Refocused, epigenetics research aligns with the field of functional genomics to provide insights into environmental and genetic influences on phenotypic variation in humans.
Abstract: Epigenetic association studies have been carried out to test the hypothesis that environmental perturbations trigger cellular reprogramming, with downstream effects on cellular function and phenotypes. There have now been numerous studies of the potential molecular mediators of epigenetic changes by epigenome-wide association studies (EWAS). However, a challenge for the field is the interpretation of the results obtained. We describe a second-generation EWAS approach, which focuses on the possible cellular models of epigenetic perturbations, studied by rigorous analysis and interpretation of genomic data. Thus refocused, epigenetics research aligns with the field of functional genomics to provide insights into environmental and genetic influences on phenotypic variation in humans.
TL;DR: This work considers this body of work in light of the key computational principles underpinning phylogenetic inference, with the goal of providing practical guidance on the design and analysis of scientifically rigorous tumour phylogeny studies.
Abstract: The use of phylogenetics in cancer genomics is increasing owing to a growing appreciation of the importance of evolutionary theory to cancer progression. The authors provide guidance on the design and analysis of tumour phylogeny studies by surveying the range of phylogenetic methods and tools available to the cancer researcher and discussing their key applications and the unsolved problems in the field.
TL;DR: This work discusses the current state of epigenomic profiling and how functional information can be indirectly inferred and presents new approaches that promise definitive functional answers, collectively referred to as 'epigenome editing', and explores CRISPR-based technologies for single-locus and multi-locate manipulation.
Abstract: A wealth of data is emerging from diverse studies of epigenomics, including genome-scale profiles of DNA methylation, histone modifications and higher-order chromatin features. In this Review, the authors discuss how, despite all this information, many challenges remain for inferring and proving the physiological and pathological functions of chromatin states. They describe the degrees of 'functionality' that are revealed by different experimental approaches, the value of integrative strategies and visions for the future.
TL;DR: Results of these investigations into the identification and characterization of the genomic and cellular traits of the protists most closely related to animals are reviewed and their implications for understanding the earliest stages of animal evolution are discussed.
Abstract: The first animals evolved from an unknown single-celled ancestor in the Precambrian period. Recently, the identification and characterization of the genomic and cellular traits of the protists most closely related to animals have shed light on the origin of animals. Comparisons of animals with these unicellular relatives allow us to reconstruct the first evolutionary steps towards animal multicellularity. Here, we review the results of these investigations and discuss their implications for understanding the earliest stages of animal evolution, including the origin of metazoan genes and genome function.
TL;DR: The strengths and weaknesses of widely used computational approaches are described, their roles in the diagnostic and discovery process are explained and how they can inform (and misinform) expert reviewers are discussed.
Abstract: When investigating Mendelian disease using exome or genome sequencing, distinguishing disease-causing genetic variants from the multitude of candidate variants is a complex, multidimensional task. Many prioritization tools and online interpretation resources exist, and professional organizations have offered clinical guidelines for review and return of prioritization results. In this Review, we describe the strengths and weaknesses of widely used computational approaches, explain their roles in the diagnostic and discovery process and discuss how they can inform (and misinform) expert reviewers. We place variant prioritization in the wider context of gene prioritization, burden testing and genotype-phenotype association, and we discuss opportunities and challenges introduced by whole-genome sequencing.
TL;DR: The elucidation of the molecular mechanisms that cause or modify the risk for different Down syndrome phenotypes could lead to the introduction of previously unimaginable therapeutic options.
Abstract: Down syndrome (also known as trisomy 21) is the model human phenotype for all genomic gain dosage imbalances, including microduplications. The functional genomic exploration of the post-sequencing years of chromosome 21, and the generation of numerous cellular and mouse models, have provided an unprecedented opportunity to decipher the molecular consequences of genome dosage imbalance. Studies of Down syndrome could provide knowledge far beyond the well-known characteristics of intellectual disability and dysmorphic features, as several other important features, including congenital heart defects, early ageing, Alzheimer disease and childhood leukaemia, are also part of the Down syndrome phenotypic spectrum. The elucidation of the molecular mechanisms that cause or modify the risk for different Down syndrome phenotypes could lead to the introduction of previously unimaginable therapeutic options.
TL;DR: The methodologies of GWAS are outlined, the current state of the field of microbial GWAS, and how lessons from human GWAS can direct the future of this field are outlined.
Abstract: The reduced costs of sequencing have led to whole-genome sequences for a large number of microorganisms, enabling the application of microbial genome-wide association studies (GWAS). Given the successes of human GWAS in understanding disease aetiology and identifying potential drug targets, microbial GWAS are likely to further advance our understanding of infectious diseases. These advances include insights into pressing global health problems, such as antibiotic resistance and disease transmission. In this Review, we outline the methodologies of GWAS, the current state of the field of microbial GWAS, and how lessons from human GWAS can direct the future of the field.
TL;DR: A recent explosion of methodological advances in exogenous labelling and single-cell sequencing have enabled lineage tracking at larger scales, in more detail, and in a wider range of species than was previously considered possible.
Abstract: Lineage analyses of multicellular organisms provide key insights into developmental mechanisms and how these developmental trajectories go awry in diverse diseases. This Review discusses the features, technical challenges and latest opportunities of an evolving range of sophisticated genetic techniques for tracking cell lineages in organisms. These strategies include methods for prospective tracking using engineered genetic constructs, as well as retrospective tracking based on naturally occurring somatic mutations.
TL;DR: Post-zygotic variation is an important confounder in medical genetic testing and a promising avenue for research: future studies could involve analyses of sorted and single cells from multiple tissue types to fully explore its potential.
Abstract: Post-zygotic variation refers to genetic changes that arise in the soma of an individual and that are not usually inherited by the next generation. Although there is a paucity of research on such variation, emerging studies show that it is common: individuals are complex mosaics of genetically distinct cells, to such an extent that no two somatic cells are likely to have the exact same genome. Although most types of mutation can be involved in post-zygotic variation, structural genetic variants are likely to leave the largest genomic footprint. Somatic variation has diverse physiological roles and pathological consequences, particularly when acquired variants influence the clonal trajectories of the affected cells. Post-zygotic variation is an important confounder in medical genetic testing and a promising avenue for research: future studies could involve analyses of sorted and single cells from multiple tissue types to fully explore its potential.
TL;DR: The interplay between replication stress and the S phase checkpoint is a key determinant of genome maintenance, and has a major impact on human diseases, notably, tumour initiation and progression.
Abstract: The interplay between replication stress and the S phase checkpoint is a key determinant of genome maintenance, and has a major impact on human diseases, notably, tumour initiation and progression. Recent studies have yielded insights into sequence-dependent and sequence-independent sources of endogenous replication stress. These stresses result in nuclease-induced DNA damage, checkpoint activation and genome-wide replication fork slowing. Several hypotheses have been proposed to account for the mechanisms involved in this complex response. Recent results have shown that the slowing of the replication forks most commonly results from DNA precursor starvation. By concomitantly increasing the density of replication initiation, the cell elicits an efficient compensatory strategy to avoid mitotic anomalies and the inheritance of damage over cell generations.
TL;DR: The informed use of reference standards, and associated statistical principles, ensures rigorous analysis of NGS data and is essential for its future clinical use.
Abstract: Technical errors can hamper the interpretation of next-generation sequencing (NGS) data, which poses a major challenge for the clinical application of this technology. This Review discusses how reference standards circumvent this issue by calibrating NGS measurements and evaluating diagnostic performance of NGS-based genetic tests. Next-generation sequencing (NGS) provides a broad investigation of the genome, and it is being readily applied for the diagnosis of disease-associated genetic features. However, the interpretation of NGS data remains challenging owing to the size and complexity of the genome and the technical errors that are introduced during sample preparation, sequencing and analysis. These errors can be understood and mitigated through the use of reference standards — well-characterized genetic materials or synthetic spike-in controls that help to calibrate NGS measurements and to evaluate diagnostic performance. The informed use of reference standards, and associated statistical principles, ensures rigorous analysis of NGS data and is essential for its future clinical use.
TL;DR: High-throughput profiling of integration sites by next-generation sequencing, combined with large-scale genomic data mining and cellular or biochemical approaches, has revealed that the insertions are usually non-random.
Abstract: Transposable elements and retroviruses are found in most genomes, can be pathogenic and are widely used as gene-delivery and functional genomics tools. Exploring whether these genetic elements target specific genomic sites for integration and how this preference is achieved is crucial to our understanding of genome evolution, somatic genome plasticity in cancer and ageing, host-parasite interactions and genome engineering applications. High-throughput profiling of integration sites by next-generation sequencing, combined with large-scale genomic data mining and cellular or biochemical approaches, has revealed that the insertions are usually non-random. The DNA sequence, chromatin and nuclear context, and cellular proteins cooperate in guiding integration in eukaryotic genomes, leading to a remarkable diversity of insertion site distribution and evolutionary strategies.
TL;DR: It will be important to understand the sources of epigenetic variation and the stability of newly formed epigenetic variants over generations to fully use the potential of epigenetics to improve crops.
Abstract: Plant breeding has traditionally relied on combining the genetic diversity present within a species to develop combinations of alleles that provide desired traits. Epigenetic diversity may provide additional sources of variation within a species that could be captured or created for crop improvement. It will be important to understand the sources of epigenetic variation and the stability of newly formed epigenetic variants over generations to fully use the potential of epigenetic variation to improve crops. The development and application of methods for widespread epigenome profiling and engineering may generate new avenues for using the full potential of epigenetics in crop improvement.
TL;DR: Cross-species comparisons of genomes, transcriptomes and gene regulation are now feasible at unprecedented resolution and throughput, enabling the comparison of human and mouse biology at the molecular level.
Abstract: Cross-species comparisons of genomes, transcriptomes and gene regulation are now feasible at unprecedented resolution and throughput, enabling the comparison of human and mouse biology at the molecular level. Insights have been gained into the degree of conservation between human and mouse at the level of not only gene expression but also epigenetics and inter-individual variation. However, a number of limitations exist, including incomplete transcriptome characterization and difficulties in identifying orthologous phenotypes and cell types, which are beginning to be addressed by emerging technologies. Ultimately, these comparisons will help to identify the conditions under which the mouse is a suitable model of human physiology and disease, and optimize the use of animal models.
TL;DR: In this paper, the authors describe parameters for choosing the optimal combination of method and system, and for interpreting phenotypes within the constraints of each method, taking into account the biological process that is targeted by each method.
Abstract: Our understanding of the genetic mechanisms that underlie biological processes has relied extensively on loss-of-function (LOF) analyses LOF methods target DNA, RNA or protein to reduce or to ablate gene function By analysing the phenotypes that are caused by these perturbations the wild-type function of genes can be elucidated Although all LOF methods reduce gene activity, the choice of approach (for example, mutagenesis, CRISPR-based gene editing, RNA interference, morpholinos or pharmacological inhibition) can have a major effect on phenotypic outcomes Interpretation of the LOF phenotype must take into account the biological process that is targeted by each method The practicality and efficiency of LOF methods also vary considerably between model systems We describe parameters for choosing the optimal combination of method and system, and for interpreting phenotypes within the constraints of each method