CRISPRi- Perturb-seq In Endothelial Cells Links Atherosclerosis Risk Loci To Novel Klf2/4 Regulatory Genes

Introduction: Genome-wide association studies (GWAS) have discovered >300 associations for CAD. Few loci are functionally characterized and may represent new mechanisms of disease. Hypothesis: Can an unbiased transcriptional screen for the >2000 candidate GWAS genes in endothelial cells (ECs) identify causal genes and disease-relevant pathways at CAD GWAS loci. Methods: We applied CRISPRi-Perturb-seq to knock down expression of genes within 500 Kb of coronary artery disease GWAS loci (2,300 genes in total) and measure their transcriptomic effects using single-cell RNA-seq. Validation of candidate causal genes was conducted in primary human ECs and zebrafish. Results: We identified 50 programs of co-expressed genes, which represent core cellular pathways (i.e. ribosome biogenesis) and 13 EC-specific pathways such as flow response and angiogenesis. The EC-specific programs show the greatest contribution to CAD heritability. 5 EC-specific programs have the greatest number of GWAS candidate genes. We find that 43 of 306 CAD GWAS signals converge onto these 5 gene programs, and all are regulated by genes in the cerebral cavernous malformations (CCM) pathway—which coordinates KLF2/4 transcriptional responses in endothelial cells, but has not been linked to CAD risk. The strongest regulator of these programs is TLNRD1 , which we show is a new CAD gene and novel regulator of the CCM pathway. TLNRD1 loss-of-function alters actin organization and barrier function in endothelial cells in vitro , and heart development in zebrafish in vivo . Conclusions: High-throughput functional analysis of 2,300 genes proximal to CAD GWAS loci prioritized pathways—such as angiogenesis and EC migration—that are regulated by multiple risk SNPs. Our study identifies new genes that likely influence risk for CAD, identifies convergence of CAD genes into certain pathways in endothelial cells, and prioritizes study of genes in the CCM-signaling pathway for contribution to CAD risk.