Human genetic variation

For clinical cases of Mendelian disease that lack a genetic diagnosis, genome and exome sequencing are increasingly used for seeking the genetic cause. This Review discusses the strategies and computational tools for prioritizing the many genetic variants identified in each genome into those that are most likely to be causal for disease. The authors discuss how diverse types of biochemical, evolutionary, pedigree and clinical-phenotype information are used, and they highlight common pitfalls to be aware of for responsible variant prioritization.

Recent microbiome genome-wide association studies have identified numerous associations between human genetic variants and the gut microbiome. Here, the authors review how genetic variation in the host can alter the composition of the gut microbiome towards a disease state, with a focus on disorders of immunity and metabolism.

Recent studies have revealed a ubiquitous role for genome architecture in the formation of structural variants at a given locus, both in DNA recombination-based and in DNA replication-based processes. These reports showcase the influence of repeat sequences on genomic stability and structural variant complexity and the tremendous plasticity and dynamic nature of our genome.

Phenotypic data from electronic health records and epidemiological studies can be exploited to study the impact of genetic variation on the phenome. This Review highlights challenges that need to be overcome for the characterization of the complex human genome–phenome relationship using phenome-wide association studies (PheWAS).

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.

The rapid accumulation and increasing quality of human DNA sequence-variation data brought about by advances in genome-scale sequencing present opportunities to investigate human evolution. The authors discuss the statistical methods and models that can be used to gain insight into the evolution of human populations from analyses of large-scale genomic data sets, as well as the challenges associated with these approaches.

With biomedical datasets growing exponentially in size and number, efforts to increase their utility and availability are essential, but much work remains to maximize exploitability. This Review summarizes trends, developments and future perspectives in the rapidly advancing field of human genotype–phenotype databases.

Many disease-associated genetic variants have been identified, but how genetic variation contributes to protection from disease is less well understood. In this Review, the authors discuss the identification and characterization of protective alleles and modifier variants, and the potential implications of these findings for disease prevention and drug development.

The wealth of existing and emerging DNA-sequencing data provides an opportunity for a comprehensive understanding of human genetic variation, including the discovery of disease-causing variants. This Review describes how the limitations of current reference-genome assemblies confound the characterization of genetic variation and how this can be mitigated by important advances in algorithms and sequencing technology that facilitate thede novoassembly of genomes.

Mitochondrial DNA (mtDNA) mutations have been associated with numerous human diseases, from severe inherited disorders to common late-onset diseases. In this Review, the authors consider the origins of these mtDNA mutations in a single cell, their spread across populations and their contributions to disease risk.

The authors provide a comprehensive survey of international legislation and policies guiding the return of whole-genome-sequencing-based genetic testing results to patients or study participants, within the context of both clinical and research settings.

A large proportion of genetic variants in the human genome have been predicted to be deleterious. This Review examines the frequency and patterns of deleterious alleles in the human genome and considers recent studies with conflicting findings on whether the mutation load, or burden of deleterious alleles, differs across populations.

High-throughput DNA sequencing technologies are providing an ever-expanding wealth of genome sequence data, including detailed information on human genetic variation. However, such data typically lack haplotype information (that is, thecis-connectivity of variants along individual chromosomes). This Review describes diverse recent experimental methods by which genetic variants can be resolved into haplotypes, accompanying computational methods and important applications of these methods in genomics and biomedical science.

Genetic variation in gene expression among individuals is an important contributor to differences in organismal phenotypes. This Review describes key concepts of such variation and provides an update on recent research on the effects of regulatory variants on the transcriptome, proteome and complex traits, including human disease risk.

Douglas Ruderfer, Shaun Purcell and colleagues characterized the rates and properties of rare genic copy number variants in exome sequencing data from nearly 60,000 individuals in the Exome Aggregation Consortium. These data are available through an integrated database that spans the spectrum of human genetic variation, aiding in the interpretation of personal genomes and population-based disease studies.

Xuejun Zhang, Jun Wang, Liangdan Sun, Lennart Hammarström and colleagues sequence the MHC region in 20,635 Han Chinese individuals. Their Han-MHC database allows identification of new susceptibility loci for psoriasis and could serve as a tool for investigating the role of the MHC region in other complex diseases.

Jonathan Marchini, Gonçalo Abecasis, Richard Durbin and colleagues describe the construction of a reference panel of human haplotypes from whole-genome sequencing data. They are able to use this to accurately impute genotypes at low minor allele frequency and present remote server resources for use by the community.

Jaume Bertranpetit, Partha Majumder and colleagues analyze whole-genome sequences from Andamanese individuals and compare them to sequences from mainland Indian and other geographically diverse populations. They find evidence of ancestry from an unknown extinct hominin in South Asian populations and show that distinct Andamanese characteristics derive from strong natural selection.

Joseph Gleeson and colleagues report whole-exome sequencing of a cohort of over 1,000 individuals from the Greater Middle East, characterizing common and rare variants. They find evidence of subregional diversity and historical migrations and use the GME Variome to identify disease-causing mutations.

Chris Tyler-Smith, Carlos Bustamante and colleagues report an analysis of 1,244 human Y chromosomes from the 1000 Genomes Project. They find that copy number variants have a higher predicted functional impact than other variant classes and infer bursts of male population expansion corresponding to historical periods of migration and technological innovations.

Matthew Hurles and colleagues sequence the genomes of three multi-sibling families and investigate the rates and spectra of germline mutation. Their analyses suggest that the mutation rate per cell division is higher during early embryogenesis than in post-pubertal spermatogenesis.

Shamil Sunyaev, Alexander Gimelbrant and colleagues report an analysis of the genetic variability in human monoallelically expressed genes. They find that genes with monoallelic expression show greater genetic diversity than biallelically expressed genes and that this diversity is associated with greater allelic age.

Albert Tenesa and colleagues report an analysis of the heritability of 12 complex diseases in 1,555,906 individuals from the UK Biobank. They find that SNP heritability explains a higher proportion of estimated heritability when shared familial environmental factors are taken into account.

Christian Gilissen, John Niederhuber and colleagues examine de novo mutations with parent-of-origin information from whole-genome sequencing datasets from 816 parent–offspring trios. They find maternal and paternal specific mutation signatures that are more prominent with increased age of the parent as well as clustered mutation signatures with no parental bias.

Elise Robinson, Mark Daly and colleagues present an analysis of genetic data from autism spectrum disorder (ASD) and population-based studies and find evidence for genetic correlations between ASDs and typical variation in social behavior and communication traits. These results may inform genetic models of ASDs and other neuropsychiatric disorders.

Varun Aggarwala and Benjamin Voight analyze human polymorphism data and develop an expanded sequence context model that explains >81% of variability in substitution probabilities, highlighting mutation-promoting motifs. Using their model, they present substitution intolerance scores for genes and a new intolerance score for amino acids, and demonstrate clinical use of the model in neuropsychiatric diseases.

Ashley Winslow, Roy Perlis, David Hinds and colleagues report the identification of 15 genetic loci associated with risk of major depressive disorder in individuals of European descent. They find that several loci are also associated with risk of other psychiatric traits, including schizophrenia and neuroticism.

Aarno Palotie and colleagues present results of a large genome-wide association study of migraine. They identified significant associations at 38 distinct loci and found enrichment for genes expressed in vascular and smooth muscle tissues.

Stephen McGarvey and colleagues identify a missense variant in CREBRF strongly associated with body mass index in Samoans. This variant is rare in other populations but is common in Samoans and has a much larger effect size than other known common obesity risk variants, including variation in FTO.

Daniel Benjamin, Meike Bartels, Philipp Koellinger and colleagues report a genome-wide association meta-analysis of subjective well-being, depressive symptoms and neuroticism. The study leverages a large sample size together with genetic correlations between the phenotypes to identify, with high confidence, loci associated with each phenotype.

Christopher Haiman, Bogdan Pasaniuc, David Reich and colleagues report a major role for low-frequency variation in the risk for prostate cancer. They show that alleles with >1% minor allele frequency contribute an order of magnitude more to risk for prostate cancer than these alleles do to overall genetic variation.

Gonçalo Abecasis, Francesco Cucca, David Schlessinger, Serena Sanna and colleagues report ~17.6 million genetic variants from whole-genome sequencing of 2,120 Sardinians. They assess the impact of these variants on circulating lipid levels and five inflammatory biomarkers.

Brendan Bulik-Sullivan, Benjamin Neale, Hilary Finucane, Alkes Price and colleagues introduce a new technique for estimating genetic correlation that requires only genome-wide association summary statistics and that is not biased by sample overlap. Using this method, they find genetic correlations between anorexia nervosa and schizophrenia, and between educational attainment and autism spectrum disorder.

Philip Awadalla and colleagues report an analysis of the relationship between recombination and deleterious variation using high-coverage sequence data from over 1,400 individuals. They find that the recombination rate modulates the distribution of putatively deleterious variants across the human genome.