Abstract 14418: Epigenetic Landscapes of Stroke Risk Haplotypes Suggest Genetic Risk Operates Through Fibroblasts

Abstract

Introduction: Genome-wide association studies (GWAS) in stroke have identified many single nucleotide polymorphisms (SNPs). However, the mechanisms behind how these SNPs confer genetic risk is unknown. Hypothesis: Stroke variants confer genetic risk by affecting non-coding DNA elements, specifically enhancers, that modulate gene expression in certain cell types. Methods: We analyzed 26 stroke risk SNPs that were validated across multiple studies. We mapped these SNPs to the associated linkage disequilibrium (LD) blocks and used chromatin immunoprecipitation-sequencing data to examine the presence of enhancer-associated histone marks (H3K27ac, H3K4me1, H3K9ac) in each block. This was performed using data for cells of the circulating blood and the vascular tissue (significant enrichment was determined by empirical p-value calculation). In cells with significant enhancer marks, HiC data was used to identify topologically associated domains (TADs) encompassing the LD blocks, which contain genes potentially affected by altered enhancer activity. Disease and biological function term enrichment was performed in Ingenuity Pathway Analysis to investigate the biological significance of these genes. Results: Fibroblasts and smooth muscle cells demonstrated significant enrichment of enhancer-associated histone marks in stroke-associated LD blocks (p<0.05). Bioinformatics analysis on TAD genes reflected enrichment of vessel development (e.g., Angiogenesis, Vasculogenesis) and fibroblast turnover (e.g., Proliferation of Fibroblast Cell Lines, Apoptosis of Fibroblast Cell Lines). Conclusion: Stroke-associated genetic variants confer risk through the vessel wall rather than circulating immune cells. Further studies are needed to experimentally confirm function of these enhancers and identity of causal variants.