Project 2 - Shh and Etv2 Signaling Pathways and Cardiovascular Repair in Mouse and Pig

ABSTRACT Cardiovascular disease is common and deadly. While lower organisms have a tremendous capacity for regeneration, the adult mammalian heart is more limited in its capacity for regeneration and remuscularization of the damaged tissue following an injury such as a myocardial infarction. Recently, we defined an evolutionary conserved Shh signaling pathway in newt and mouse that promotes cardiomyocyte proliferation in vitro and cardiac repair. Our preliminary data support the hypothesis that Gli1 (a downstream effector of Shh) is a direct upstream regulator of Sox4 gene expression and Gli1 overexpression promotes cardiomyocyte proliferation in vitro. Furthermore, we have demonstrated that Etv2 is a master regulator of the endothelial lineage and is necessary and sufficient for angiogenesis in mouse and pig. Importantly, the results of these studies provide a platform for the proposed studies that will dissect the mechanisms that govern cardiovascular repair and proliferation. Therefore, our overall hypothesis is that the Shh downstream effectors, Gli1/Gli2, regulate cardiomyocyte proliferation in a Sox4 dependent manner and Etv2 promotes endothelial/vascular development to collectively promote cardiac regeneration. In these proposed studies, we will use a number of novel genetic models and large animal models that are available in our laboratory (and the cores), bioinformatics algorithms that we developed and we take an innovative approach to dissect the role of Gli1, Etv2 and Sox4 as important factors that govern cardiovascular repair and proliferation. To examine our hypotheses, the revised Project 2 proposal will address the following specific aims: Specific Aim #1: To define the capacity of Gli and Etv2 deficient hearts for growth and regeneration; Specific Aim #2: To determine the impact of Gli1 and Etv2 overexpression on cardiac repair and regeneration and Specific Aim #3: To define the mechanistic role of Sox4 in the cardiomyocyte lineage. These aims will complement and synergize with the other projects. They will utilize our recently engineered genetic mouse models, inducible viral vectors, modified mRNA-GFP constructs, mouse and pig models, molecular analyses and bioinformatics algorithms to comprehensively define the role for Gli1, Etv2 and Sox4 as essential factors that govern cardiac repair and regeneration by promoting cardiomyocyte proliferation and angiogenesis following injury. Given the tremendous morbidity and mortality of cardiovascular disease in our society, the potential impact of this proposal is tremendous.