9p21 DNA variants associated with coronary artery disease impair interferon-γ signalling response

Abstract

A non-coding region on chromosome 9p21 was previously shown to associate with coronary artery disease and type 2 diabetes, and the region has been implicated in regulating neighbouring genes. Here the authors identify 33 distinct enhancers within this region and show that single nucleotide polymorphisms in one of the enhancers affect STAT1 binding. They further show that in human vascular endothelium cells, the enhancer interval physically interacts with a number of specific loci, and that interferon-γ activation strongly affects the chromatin structure and transcriptional regulation of the 9p21 locus, including STAT1 binding, long-range enhancer interactions and expression of neighbouring genes. A non-coding region on chromosome 9p21 was previously shown to associate with coronary artery disease and type 2 diabetes, and the region has been implicated in regulating neighbouring genes. Here, 33 distinct enhancers within this region are identified, showing that SNPs in one of the enhancers affect STAT1 binding. Furthermore, it is shown that in human vascular endothelial cells the enhancer interval physically interacts with a number of specific loci and that IFN-γ activation strongly affects the chromatin structure and transcriptional regulation of the 9p21 locus, including STAT1 binding, long-range enhancer interactions and expression of neighbouring genes. Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) in the 9p21 gene desert associated with coronary artery disease (CAD)1,2,3,4 and type 2 diabetes5,6,7. Despite evidence for a role of the associated interval in neighbouring gene regulation8,9,10, the biological underpinnings of these genetic associations with CAD or type 2 diabetes have not yet been explained. Here we identify 33 enhancers in 9p21; the interval is the second densest gene desert for predicted enhancers and six times denser than the whole genome (P < 6.55 × 10−33). The CAD risk alleles of SNPs rs10811656 and rs10757278 are located in one of these enhancers and disrupt a binding site for STAT1. Lymphoblastoid cell lines homozygous for the CAD risk haplotype show no binding of STAT1, and in lymphoblastoid cell lines homozygous for the CAD non-risk haplotype, binding of STAT1 inhibits CDKN2BAS (also known as CDKN2B-AS1) expression, which is reversed by short interfering RNA knockdown of STAT1. Using a new, open-ended approach to detect long-distance interactions, we find that in human vascular endothelial cells the enhancer interval containing the CAD locus physically interacts with the CDKN2A/B locus, the MTAP gene and an interval downstream of IFNA21. In human vascular endothelial cells, interferon-γ activation strongly affects the structure of the chromatin and the transcriptional regulation in the 9p21 locus, including STAT1-binding, long-range enhancer interactions and altered expression of neighbouring genes. Our findings establish a link between CAD genetic susceptibility and the response to inflammatory signalling in a vascular cell type and thus demonstrate the utility of genome-wide association study findings in directing studies to novel genomic loci and biological processes important for disease aetiology.