Chromatin accessibility and gene expression during adipocyte differentiation identify context-dependent effects at cardiometabolic GWAS loci [RNA-seq]

Chromatin accessibility and gene expression in relevant cell contexts can guide identification of regulatory elements and mechanisms at genome-wide association study (GWAS) loci. To identify regulatory elements that display differential activity across adipocyte differentiation, we performed ATAC-seq and RNA-seq in a cell model of preadipocytes and adipocytes at days 4 and 14 of differentiation. For comparison, we created a consensus map of ATAC-seq peaks in 11 subcutaneous adipose tissue samples. A set of 15,919 adipocyte-dependent peaks showed stronger enrichment (60.1%) of adipocyte nuclei enhancers than 51,855 adipose tissue peaks (44.6%) or 18,244 preadipocyte-dependent peaks (11.5%). We linked context-dependent peaks to genes based on adipocyte promoter capture Hi-C data, overlap with adipose eQTL variants, and differential gene expression. Of 16,167 context-dependent peaks that could be linked to a gene, 5,184 were linked by two or more strategies to 1,675 genes. Among GWAS loci for cardiometabolic traits, adipocyte peaks showed the strongest enrichment for waist-to-hip ratio, coronary artery disease, and HDL-cholesterol, while adipose tissue peaks also showed significant enrichment for LDL-cholesterol and triglyceride levels. We identified 666 peaks linked to 507 genes by two or more methods and overlapping a GWAS signal, suggesting a regulatory mechanism at these loci. At one GWAS locus for palmitoleic acid, rs603424 was located in an adipocyte-dependent peak linked to SCD and exhibited allelic differences in transcriptional activity in adipocytes (P=0.003) but not preadipocytes (P=0.09). These results demonstrate that context-dependent peaks and genes can guide discovery of regulatory variants at GWAS loci and aid identification of regulatory mechanisms. Overall design: RNA-seq on SGBS preadipocytes and adipocytes at days 0, 2, 4, and 14 of differentiation