Project 2: Smooth muscle cell programs for coronary artery disease

Project 2 With the identification of over 300 replicated loci, genome wide association studies (GWAS) have provided the first opportunity for the discovery of cellular and molecular pathways that regulate risk for coronary artery disease (CAD). Genomic studies employing these data have indicated that much of CAD risk resides in endothelial cell (EC) and smooth muscle cell (SMC) lineages. Our studies have identified and linked a small number of causal genes to complex phenotypic transitions in SMCs. We have shown that genes protective toward disease risk, such as TCF21 and SMAD3, promote SMC transition to a fibroblast-like fibromyocyte (FMC) phenotype and inhibit transition to a chondrogenic chondromyocyte (CMC) phenotype, while risk-promoting genes like PDGFD promote the development of CMCs. We are just beginning to link GWAS loci genes together into biological pathways, in an effort to map causal cellular and molecular mechanisms of disease risk. However, study of individual loci in isolation is slow and arduous, is costly and requires years of work for each locus gene. A critical need in the field is to expand the number of causal genes in GWAS associated loci and link them together in specific programs, thus extending available knowledge and promoting further mechanistic studies to validate and explore their relevant biology. Furthermore, while similar SMC transitions have been observed in other diseases such as pulmonary artery hypertension (PAH), it remains unclear how the disease gene programs underlying these transitions may have functions specific to one or another vascular bed, and how they may influence neighboring EC phenotypes. To address these questions, we will leverage technologies from our Perturb-seq and Mouse Model Cores, and collaborations with Projects 1 and 3, to systematically map these SMC gene programs, and evaluate how they modulate SMC transition states and interact with ECs to regulate the atherosclerotic process. Our hypothesis for Project 2 is that many CAD GWAS loci converge to affect a small number of shared gene programs that regulate SMC transition phenotypes in human coronary SMCs, and signal to neighboring ECs to modulate a coordinated response to vascular stress. We will investigate this hypothesis with the following Aims. In Aim 1, we will perform in vitro CRISPRi screens in human coronary artery SMCs to identify candidate causal genes in CAD associated loci, and map their convergence onto shared gene programs. In Aim 2, we will further study the CAD genes identified in Aim 1 with classical in vivo gene targeting in mouse models, focusing on those that affect SMC phenotype and communication to neighboring EC. In Aim 3, we will perform in vivo perturb-seq in ECs on the background of SMC-specific Smad3 KO to investigate the crosstalk between SMCs and ECs. Together, these studies will provide an unprecedented advance toward understanding the mechanisms by which CAD genes expressed in SMC mediate disease risk directly through regulating phenotypic transitions, and indirectly through mediating SMC-EC crosstalk. Project Number: 1P01HL180323-01 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: THOMAS QUERTERMOUS | Institution: STANFORD UNIVERSITY, STANFORD, CA | Award Amount: $501,611 | Activity Code: P01 | Study Section: Heart, Lung, and Blood Program Project Study Section[HLBP (MA)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1P01HL18032301