Identification of epistasis affecting complex human traits has been challenging. Focusing on known coronary artery disease (CAD) risk loci, we explore pairwise statistical interactions between 8,068 SNPs from ten CAD genome-wide association studies (n=30,180). We discovered rs1800769 and rs9458001 in the vicinity of the LPA locus to interact in modulating CAD risk (P=1.75e-13). Specific genotypes (e.g., rs1800769 CT) displayed either significantly decreased or increased risk for CAD in the context of genotypes of the respective other SNP (e.g., rs9458001 GG vs. AA). In the UK Biobank (n=450,112) significant interaction of this SNP pair was replicated for CAD (P=3.09e-22), and was also found for aortic valve stenosis (P=6.95e-7) and peripheral arterial disease (P=2.32e-4). Identical interaction patterns affected circulating lipoprotein(a) (n=5,953; P=8.7e-32) and hepatic apolipoprotein(a) (apo(a)) expression (n=522, P=2.6e-11). We further interrogated potential biological implications of the variants and propose a mechanism explaining epistasis that ultimately may translate to substantial cardiovascular risks.

Cis-epistasis at the LPA locus and risk of coronary artery disease