Abstract 218: Integration Of Coronary Artery Disease GWAS With Bulk And Single-cell Transcriptomics From Atherosclerotic Plaques By Deconvolution, Reveals Novel Smooth Muscle Cell Genes

Abstract

Background and Aim: A central role of vascular smooth muscle cells (SMCs) in atherosclerosis has recently evolved that suggests causal genetic links to disease processes. Single cell sequencing studies of atherosclerotic plaques have identified multiple mesenchymal transition cell populations within the plaques. Here, we correlated cell fractions from plaques to coronary artery disease (CAD) related gene polymorphisms to identify novel SMC targets and study their influence on SMC function in atherosclerosis. Methods: Deconvolution analysis was performed on bulk microarray data from carotid plaques in the Biobank of Karolinska Endarterectomies (BiKE, n=127) using single cell sequencing data from coronary plaques (n=5). CAD-associated GWAS loci associated with mesenchymal cell fractions were identified, followed by functional analyses of these genes in SMC in vitro using migration, proliferation and apoptosis assays. Results: We identified 5 mesenchymal cell-specific genetic variants associated with CAD, BiKE patient symptomatology and gene expression eQTLs in BiKE plaque tissue and GTex normal arteries. These variants were harbored in genetic loci of ARNTL, LDLR, MIA3, PAK1 and ARHGAP15 . Microarray analysis revealed increased expression of ARHGAP15 and PAK1 and decreased levels of LDLR in carotid plaques compared with normal arteries (n=127 vs. 10 respectively, student’s t-test). Immunohistochemistry demonstrated increased expression of corresponding proteins in the fibrous cap of plaques compared to normal arteries (n=5). To investigate their function in SMCs, the genes were silenced using siRNAs followed by migration, proliferation and apoptosis assays. Preliminary results indicated that silencing of MIA3, LDLR and ARNTL inhibited SMC proliferation. Conclusions: The results of this project may reveal novel SMC-specific genetic links to the disease, which may serve as therapeutic targets to be explored for improved treatment of atherosclerosis.