Abstract 13554: High-Throughput Investigation of Human Genes and Variants Affecting LDL Cholesterol Uptake

Abstract

Introduction: Genetic differences in cholesterol metabolism are major contributors to the risk of coronary artery disease (CAD), which is the leading cause of death in the USA. Genome-wide association screens have identified over 300 independent genomic loci where genetic variation is associated with serum LDL cholesterol (LDL-C) levels. While several of these loci are important drug targets, for the vast majority of loci, it is unknown which exact genetic variants, genes and cellular pathways are impacted by these variants. Hypothesis: We hypothesize that combining high-throughput CRISPR-Cas9 screening, gene clustering and network analysis, and human genetic biobank cohort analysis will increase our power to reveal the genetic basis behind human variation in cholesterol levels. Methods: We have devised sensitive high-throughput CRISPR-Cas9-based screens to gain insight into the genetic mechanisms that impact cellular cholesterol metabolism. Results: Through a combination of CRISPR-Cas9-nuclease and CRISPR base editing screens, we have identified hundreds of human genes and GWAS-associated variants that influence cellular LDL-C uptake in liver cells. We have developed experimental and computational methods to group these genes into biological pathways, uncovering previously unappreciated cellular mechanisms driving variation in LDL-C uptake. We have connected these novel LDL-C uptake-altering genes and pathways to serum LDL-C levels by analyzing rare coding variant burden from a UK Biobank exome sequencing cohort, identifying functional gene modules for which damaging coding variants in the population have significant effects LDL-C levels. Finally, we have identified GWAS-associated non-coding variants that alter LDL-C uptake through modulating expression of previously unappreciated cholesterol-related genes. Conclusions: Through high-throughput CRISPR screening followed by mechanistic follow-up, we have made progress in dissecting the non-coding loci, genes, and pathways that underlie variation in human cellular cholesterol uptake.