Genomic profiling of human vascular cells identifies TWIST1 as a causal gene for common vascular diseases

Author summary Genome-wide association studies (GWAS) have identified hundreds of genetic variants that are associated with human vascular disease including coronary artery disease. These are predominantly common single nucleotide polymorphisms (SNPs) in non-coding regions, which makes the identification of the causal genes and their underlying connection to pathophysiology challenging. Mapping of expression quantitative trait loci (eQTLs) has been performed to associate GWAS SNPs with risk genes in vascular cells and tissues. However, atherosclerotic vascular tissues contain multiple cell types. We perform deep transcriptomic profiling of genotyped human-derived vascular cells-endothelial cells and smooth muscle cells-and use splicing quantitative trait locus, allele-specific expression, and colocalization analyses to annotate genetic variants associated with vascular diseases and gain insight into their potential function in a cell-type specific manner. Based on these analyses, we identified computationally and then validate experimentally an association between the CAD risk locus rs2107595 and the gene TWIST1. We propose that the minor allele for this locus can affect transcription factor binding and provide data supporting a role for TWIST1 in modulating smooth muscle cell phenotype. Genome-wide association studies have identified multiple novel genomic loci associated with vascular diseases. Many of these loci are common non-coding variants that affect the expression of disease-relevant genes within coronary vascular cells. To identify such genes on a genome-wide level, we performed deep transcriptomic analysis of genotyped primary human coronary artery smooth muscle cells (HCASMCs) and coronary endothelial cells (HCAECs) from the same subjects, including splicing Quantitative Trait Loci (sQTL), allele-specific expression (ASE), and colocalization analyses. We identified sQTLs for TARS2, YAP1, CFDP1, and STAT6 in HCASMCs and HCAECs, and 233 ASE genes, a subset of which are also GTEx eGenes in arterial tissues. Colocalization of GWAS association signals for coronary artery disease (CAD), migraine, stroke and abdominal aortic aneurysm with GTEx eGenes in aorta, coronary artery and tibial artery discovered novel candidate risk genes for these diseases. At the CAD and stroke locus tagged by rs2107595 we demonstrate colocalization with expression of the proximal gene TWIST1. We show that disrupting the rs2107595 locus alters TWIST1 expression and that the risk allele has increased binding of the NOTCH signaling protein RBPJ. Finally, we provide data that TWIST1 expression influences vascular SMC phenotypes, including proliferation and calcification, as a potential mechanism supporting a role for TWIST1 in CAD.