SMYD2 promoter DNA methylation is associated with abdominal aortic aneurysm (AAA) and expression in vascular smooth muscle cells.

Abstract

We assessed global methylation in peripheral blood mononuclear cell DNA from 92 individuals with AAA and 93 controls using enzyme-linked immunosorbent assays, identifying hyper-methylation in those with large AAA and a positive linear association with AAA diameter (P < 0.0001, R2 = 0.3175).We then determined CpG methylation status of regulatory regions in genes located at AAA risk loci identified in genome-wide association studies, using bisulphite next-generation sequencing (NGS) in vascular smooth muscle cells (VSMCs) taken from aortic tissues of 44 individuals (24 AAAs and 20 controls). In IL6R, 2 CpGs were hyper-methylated (P = 0.0145); in ERG, 13 CpGs were hyper-methylated (P = 0.0005); in SERPINB9, 6 CpGs were hypo-methylated (P = 0.0037) and 1 CpG was hyper-methylated (P = 0.0098); and in SMYD2, 4 CpGs were hypo-methylated (P = 0.0012).RT-qPCR was performed for each differentially methylated gene on mRNA from the same VSMCs and compared with methylation. This analysis revealed downregulation of SMYD2 and SERPINB9 in AAA, and a direct linear relationship between SMYD2 promoter methylation and SMYD2 expression (P = 0.038). Furthermore, downregulation of SMYD2 at the site of aneurysm in the aortic wall was further corroborated in 6 of the same samples used for methylation and gene expression analysis with immunohistochemistry.