The Cellular and Molecular Role ofGATA4 in Bicuspid Aortic Valve Disease

About This Grant

PROJECT SUMMARY Bicuspid aortic valve (BAV) is the most common congenital cardiovascular malformation, characterized by the fusion of two rather than three aortic valve leaflets, and predisposing affected individuals to severe complications including aortic regurgitation, infective endocarditis, and aortic dissection. Despite its prevalence, the molecular mechanisms that govern BAV formation remain poorly understood. Through exome sequencing of a family with inherited BAV, we identified a missense variant in the transcription factor GATA4 (GATA4S377G) that we hypothesize drives the disease. Introduction of this single nucleotide variant into mice produced BAV in 43 percent of animals, establishing the first genetically precise mouse model of BAV caused by a single point mutation. This discovery provides an unprecedented opportunity to mechanistically define how a specific human GATA4 variant alters valve morphogenesis. In Aim 1, we will comprehensively characterize the Gata4S379G mouse model, quantifying birth rates, mortality, and sex-specific penetrance, and assessing cardiac structure and function by echocardiography and magnetic resonance imaging. In Aim 2, we will apply single-cell RNA sequencing, spatial transcriptomics, and HiChIP to define the cell type-specific regulatory networks disrupted by mutant Gata4 during valve morphogenesis, revealing how altered AP- 1/NFAT/TNFα signaling reprograms transcriptional and chromatin architecture to drive abnormal cusp formation. In Aim 3, we will use patient-derived and isogenic human induced pluripotent stem cells (iPSCs) carrying the GATA4S377G mutation to define how this variant disrupts transcriptional regulation, chromatin architecture, and cellular function across key cardiac lineages: endocardial cells, fibroblasts, and cardiomyocytes. Using multi-omic integration and functional assays of endothelial-to-mesenchymal transition, extracellular matrix remodeling, and cell viability, we will determine how dysregulated AP-1/NFAT/TNFα signaling drives abnormal valve cell behavior. Pharmacologic rescue experiments will test whether correcting AP-1/NFAT activity restores normal phenotypes. Together, these studies will integrate in vivo and human iPSC systems to establish a mechanistic framework linking GATA4-driven transcriptional dysregulation to bicuspid aortic valve pathogenesis and identify actionable molecular targets for therapy.