A framework for detecting noncoding rare variant associations of large-scale whole-genome sequencing studies

Large-scale whole-genome sequencing studies have enabled analysis of noncoding rare variants' (RVs) associations with complex human traits. Variant set analysis is a powerful approach to study RV association, and a key component of it is constructing RV sets for analysis. However, existing methods have limited ability to define analysis units in the noncoding genome. Furthermore, there is a lack of robust pipelines for comprehensive and scalable noncoding RV association analysis. Here we propose a computationally-efficient noncoding RV association-detection framework that uses STAAR (variant-set test for association using annotation information) to group noncoding variants in gene-centric analysis based on functional categories. We also propose SCANG (scan the genome)-STAAR, which uses dynamic window sizes and incorporates multiple functional annotations, in a non-gene-centric analysis. We furthermore develop STAARpipeline to perform flexible noncoding RV association analysis, including gene-centric analysis as well as fixed-window-based and dynamic-window-based non-gene-centric analysis. We apply STAARpipeline to identify noncoding RV sets associated with four quantitative lipid traits in 21,015 discovery samples from the Trans-Omics for Precision Medicine (TOPMed) program and replicate several noncoding RV associations in an additional 9,123 TOPMed samples.

A compendium of uniformly processed human gene expression and splicing quantitative trait loci

Many gene expression quantitative trait locus (eQTL) studies have published their summary statistics, which can be used to gain insight into complex human traits by downstream analyses, such as fine mapping and co-localization. However, technical differences between these datasets are a barrier to their widespread use. Consequently, target genes for most genome-wide association study (GWAS) signals have still not been identified. In the present study, we present the eQTL Catalogue (https://www.ebi.ac.uk/eqtl), a resource of quality-controlled, uniformly re-computed gene expression and splicing QTLs from 21 studies. We find that, for matching cell types and tissues, the eQTL effect sizes are highly reproducible between studies. Although most QTLs were shared between most bulk tissues, we identified a greater diversity of cell-type-specific QTLs from purified cell types, a subset of which also manifested as new disease co-localizations. Our summary statistics are freely available to enable the systematic interpretation of human GWAS associations across many cell types and tissues.

The individual and global impact of copy number variants on complex human traits

Copy number variations (CNVs) have been involved in multiple genomic disorders but their impact on complex traits remains understudied. We called CNVs in the UK Biobank and performed genome-wide association scans (GWASs) between the copy-number of CNV-proxy probes and 57 continuous traits, revealing 131 signals spanning 47 phenotypes. Our analysis recapitulated well-known associations (1q21 and height), revealed the pleiotropy of recurrent CNVs (26 traits for 16p11.2-BP4-BP5), and suggested new gene functionalities (MARF1 in female reproduction). Forty CNV signals overlapped known GWAS loci (RHD deletion and hematological traits). Conversely, others overlapped Mendelian disorder regions, suggesting variable expressivity and a broad impact of these loci, as illustrated by signals mapping to Rotor syndrome (SLCO1B1/3), renal cysts and diabetes (HNF1B), or Charcot-Marie-Tooth (PMP22) loci. The total CNV burden negatively impacted 35 traits, leading to increased adiposity, liver/kidney damage, and decreased intelligence and physical capacity. Thirty traits remained burden-associated after correcting for CNV-GWAS signals, pointing to a polygenic CNV-architecture. The burden negatively correlated with socio-economic indicators, parental lifespan, and age (survivorship proxy), suggesting that CNVs contribute to decreased longevity. Together, our results showcase how studying CNVs can reveal new biological insights, emphasizing the critical role of this mutational class in shaping complex traits.

An autoimmune disease risk variant: A trans master regulatory effect mediated by IRF1 under immune stimulation?

Functional mechanisms remain unknown for most genetic loci associated to complex human traits and diseases. In this study, we first mapped trans-eQTLs in a data set of primary monocytes stimulated with LPS, and discovered that a risk variant for autoimmune disease, rs17622517 in an intron of C5ORF56, affects the expression of the transcription factor IRF1 20 kb away. The cis-regulatory effect specific to IRF1 is active under early immune stimulus, with a large number of trans-eQTL effects across the genome under late LPS response. Using CRISPRi silencing, we showed that perturbation of the SNP locus downregulates IRF1 and causes widespread transcriptional effects. Genome editing by CRISPR had suggestive recapitulation of the LPS-specific trans-eQTL signal and lent support for the rs17622517 site being functional. Our results suggest that this common genetic variant affects inter-individual response to immune stimuli via regulation of IRF1. For this autoimmune GWAS locus, our work provides evidence of the functional variant, demonstrates a condition-specific enhancer effect, identifies IRF1 as the likely causal gene in cis, and indicates that overactivation of the downstream immune-related pathway may be the cellular mechanism increasing disease risk. This work not only provides rare experimental validation of a master-regulatory trans-eQTL, but also demonstrates the power of eQTL mapping to build mechanistic hypotheses amenable for experimental follow-up using the CRISPR toolkit.

Modeling regulatory network topology improves genome-wide analyses of complex human traits

Genome-wide association studies (GWAS) have cataloged many significant associations between genetic variants and complex traits. However, most of these findings have unclear biological significance, because they often have small effects and occur in non-coding regions. Integration of GWAS with gene regulatory networks addresses both issues by aggregating weak genetic signals within regulatory programs. Here we develop a Bayesian framework that integrates GWAS summary statistics with regulatory networks to infer genetic enrichments and associations simultaneously. Our method improves upon existing approaches by explicitly modeling network topology to assess enrichments, and by automatically leveraging enrichments to identify associations. Applying this method to 18 human traits and 38 regulatory networks shows that genetic signals of complex traits are often enriched in interconnections specific to trait-relevant cell types or tissues. Prioritizing variants within enriched networks identifies known and previously undescribed trait-associated genes revealing biological and therapeutic insights.

A model and test for coordinated polygenic epistasis in complex traits

Interactions between genetic variants—epistasis—is pervasive in model systems and can profoundly impact evolutionary adaption, population disease dynamics, genetic mapping, and precision medicine efforts. In this work, we develop a model for structured polygenic epistasis, called coordinated epistasis (CE), and prove that several recent theories of genetic architecture fall under the formal umbrella of CE. Unlike standard epistasis models that assume epistasis and main effects are independent, CE captures systematic correlations between epistasis and main effects that result from pathway-level epistasis, on balance skewing the penetrance of genetic effects. To test for the existence of CE, we propose the even-odd (EO) test and prove it is calibrated in a range of realistic biological models. Applying the EO test in the UK Biobank, we find evidence of CE in 18 of 26 traits spanning disease, anthropometric, and blood categories. Finally, we extend the EO test to tissue-specific enrichment and identify several plausible tissue–trait pairs. Overall, CE is a dimension of genetic architecture that can capture structured, systemic forms of epistasis in complex human traits.

Identifying the genetic basis and molecular mechanisms underlying phenotypic correlation between complex human traits using a gene-based approach

Phenotypic correlations between complex human traits have long been observed based on epidemiological studies. However, the genetic basis and underlying mechanisms are largely unknown. The recent accumulation of GWAS data has made it possible to analyze the genetic similarity between human traits through comparative analysis. Here we developed a gene-based approach to measure genetic similarity between a pair of traits and to delineate the shared genes/pathways, through three steps: 1) translating SNP-phenotype association profile to genephenotype association profile by integrating GWAS with eQTL data; 2) measuring the similarity between a pair of traits by a normalized distance between the two gene-phenotype association profiles; 3) delineating genes/pathways supporting the similarity. Application of this approach to a set of GWAS data covering 59 human traits detected significant similarity between many known and unexpected pairs of traits; a significant fraction of them are not detectable by SNP based similarity measures. Examples include Height and Schizophrenia, Cancer and Alzheimer’s Disease, and Rheumatoid Arthritis and Crohn’s disease. Functional analysis revealed specific genes/pathways shared by these pairs. For example, Height and Schizophrenia are co-associated with genes involved in neural development, skeletal muscle regeneration, protein synthesis, magnesium homeostasis, and immune response, suggesting growth and development as a common theme underlying both traits. Our approach can detect yet unknown relationships between complex traits and generate mechanistic hypotheses, and has the potential to improve diagnosis and treatment by transferring knowledge from one disease to another.

Identifying the genetic basis and molecular mechanisms underlying phenotypic correlation between complex human traits using a gene-based approach

Phenotypic correlations between complex human traits have long been observed based on epidemiological studies. However, the genetic basis and underlying mechanisms are largely unknown. The recent accumulation of GWAS data has made it possible to analyze the genetic similarity between human traits through comparative analysis. Here we developed a gene-based approach to measure genetic similarity between a pair of traits and to delineate the shared genes/pathways, through three steps: 1) translating SNP-phenotype association profile to gene-phenotype association profile by integrating GWAS with eQTL data; 2) measuring the similarity between a pair of traits by a normalized distance between the two gene-phenotype association profiles; 3) delineating genes/pathways supporting the similarity. Application of this approach to a set of GWAS data covering 59 human traits detected significant similarity between many known and unexpected pairs of traits; a significant fraction of them are not detectable by SNP based similarity measures. Examples include Height and Schizophrenia, Cancer and Alzheimer’s Disease, and Rheumatoid Arthritis and Crohn’s disease. Functional analysis revealed specific genes/pathways shared by these pairs. For example, Height and Schizophrenia are co-associated with genes involved in neural development, skeletal muscle regeneration, protein synthesis, magnesium homeostasis, and immune response, suggesting growth and development as a common theme underlying both traits. Our approach can detect yet unknown relationships between complex traits and generate mechanistic hypotheses, and has the potential to improve diagnosis and treatment by transferring knowledge from one disease to another.

Signatures Of Tspan8 Variants Associated With Human Metabolic Regulation And Diseases

Here, with the example of common copy number variation (CNV) in the TSPAN8 gene, we present an important piece of work in the field of CNV detection, CNV association with complex human traits such as 1H NMR metabolomic phenotypes and an example of functional characterization of CNVs among human induced pluripotent stem cells (HipSci). We report TSPAN8 exon 11 as a new locus associated with metabolomic regulation and show that its biology is associated with several metabolic diseases such as type 2 diabetes (T2D), obesity and cancer. Our results further demonstrate the power of multivariate association models over univariate methods and define new metabolomic signatures for several new genomic loci, which can act as a catalyst for new diagnostics and therapeutic approaches.