338 Interferon alpha 21 levels are elevated in peripheral blood lymphocytes and aortic smooth muscle cells with the 9p21.3 coronary artery disease risk genotype

Abstract

The 9p21.3 locus confers risk for coronary artery disease (CAD) by an unknown mechanism. A recent report identified several long-range enhancers, at CDKN2B, CDKN2A, MTAP and between the interferon omega-1 (IFNW1) and interferon alpha-21 (IFNA21) genes, whose chromatin structure is influenced by single nucleotide polymorphisms within the 9p21.3 risk locus as far as 1 million base pairs away. However, whether protein expression from the genes in the vicinity of these long-range enhancers is correlated with the 9p21.3 risk genotype was not known. Here, we applied immunoblot analysis using antibodies specific to the proteins encoded by the genes near the long-range enhancers to test for their association with the 9p21.3 risk genotype. Using protein extracts from primary cultures of human aortic smooth muscle cells (n = 6) and peripheral blood lymphocytes from patients with CAD (n = 18) genotyped for the 9p21.3 risk locus using SNP microarrays, we found a clear positive correlation (P < 10-4) between IFNA21 levels and 9p21.3 risk genotype in both cell types. No association between MTAP expression and 9p21.3 genotype was seen in either cell type. In contrast, CDKN2A protein expression in both cell types, and CDKN2B protein expression in aortic smooth muscle cells was negatively associated with 9p21.3 risk genotype. Thus, the presence of long-range enhancers influenced by the 9p21.3 risk locus does not predict the direction of associated gene expression. Elevated IFNA21 and reduced CDKN2A protein expression is linked to and likely accounts for the risk of CAD associated with the 9p21.3 locus.