Abstract 53: Transcriptomics and Methylomics of Atherosclerosis in Circulating Monocytes - the Multi-Ethnic Study of Atherosclerosis

Little is known regarding the transcriptional and epigenetic basis for atherogenesis and cardiovascular disease (CVD) risk. Here we integrate transcriptomic (Illumina HumanHT-12 v4) and methylomic (Illumina 450K array) data from purified monocytes with concurrent CVD risk factors and measures of atherosclerosis - carotid plaque (CP) identified using ultrasound and coronary artery calcium (CAC), from 1,208 randomly selected participants (554 whites, 260 blacks, 394 Hispanics) of the Multi-Ethnic Study of Atherosclerosis (MESA). Association analysis was performed using linear and logistic regression, adjusting for demographics, technical covariates, and other known CVD risk factors. A false discovery rate (FDR) <0.05 was used to control for multiple comparisons. RESULTS: We identified expression of two genes, ARID5B (a transcription factor) and PDLIM7, positively associated with both CP and CAC, and 17 additional genes associated with only CAC . We also identified 29 and seven differentially methylated CpGs associated with CP and CAC, respectively, including a CpG at ILVBL associated with both CP and CAC. Eleven of these atherosclerosis CpGs were also associated with cis-gene expression, including an ARID5B expression-associated methylation site (cg25953130, ARID5B intron) which overlapped a predicted strong enhancer, a transcription factor binding site (for EP300), and a DNase I hotspot (ENCODE and BLUEPRINT monocyte data). The inverse association between methylation of this ARID5B CpG and atherosclerosis (CP:p=4.3x10-7, FDR=0.01; CAC: p= 2.4x10-5, FDR=0.32) appeared to be mediated through ARID5B expression (CP: p=2.1x10-4, CAC: p=2.1 x10-3, using Structural Equation modeling with bootstrapping). Furthermore, many other known risk factors for CVD (age, ethnicity, body mass index, diabetes, HDL, and interleukin-6 levels) were also associated with ARID5B expression at genome-wide levels of significance. The ARID5B associations with atherosclerosis at gene expression and methylation levels together explain an additional 2.3% variability in CP above and beyond known CVD risk factors, and were consistent across age (< or ≥65 years), sex, race/ethnicity, CVD status, or statin use subgroups, as well as the independent sites of data collection. ARID5B expression was also positively associated with prevalent CVD (p=0.006). CONCLUSIONS: The concurrent multi-omic profiling of atherogenic-related cells coupled with state-of-the-art measurements of atherosclerosis in a large, well-phenotyped, multi-ethnic cohort provide novel insights into the biomarkers and the potential molecular mechanisms of atherosclerosis. In particular, our data on ARID5B , taken together with previously reported experimental evidence for its role in promoting lipid accumulation and smooth muscle cell differentiation, strongly suggests an atherogenic role for this gene.