Cardiovascular diseases are both common and deadly. For example, peripheral artery disease affects more than 10M Americans resulting in more than 150,000 limb amputations each year in the U.S. In addition, more than 300,000 patients have coronary artery bypass grafting (surgical revascularization). Current medical therapies for vascular disease include limb amputation and vascular bypass grafting--these therapeutic interventions have significant limitations. These diseases are chronic, debilitating, lethal and they warrant new and novel therapies. Previous studies have demonstrated the essential role for pioneer factors that modulate chromatin accessibility and thereby impact the binding of early transcriptional regulators for lineage specification. We have recently demonstrated that ETV2 is an essential pioneer factor for endothelial, vascular and blood lineages. We have used global and conditional gene disruption strategies, fate-mapping, gene editing, single cell RNA-seq, ATAC-seq and ChIP-seq assays to provide supportive data for this application. In addition, we defined an important ETV2-miR130a-PDGFRa cascade that governs endothelial development. Furthermore, our recent publications and our preliminary data support the overall hypothesis that ETV2 is a pioneer factor that regulates the specification of the endothelial lineage. In these proposed studies, we will use a number of unique genetic models that we have engineered and we take an innovative strategy to define the mechanisms whereby ETV2 functions as a pioneer factor to regulate cardiovascular regeneration. To examine our hypotheses, we will address the following specific aims: Specific Aim #1: Specific Aim #1: To further define the mechanisms whereby ETV2 functions as a pioneer factor during embryogenesis and reprogramming to the endothelial lineage; Specific Aim #2: To define the role of chromatin modifying factors and ETV2 during embryogenesis and reprogramming to the endothelial lineage and Specific Aim #3: To examine the factors that promote ETV2 mediated reprogramming of the endothelial lineage in vitro and in vivo. These aims will utilize our recently engineered genetic mouse models, ATAC-seq, MNase-seq, ChIP-seq, inducible mouse model, cardiac injury model in the adult mouse, novel and bioinformatics algorithms to comprehensively define the mechanisms whereby ETV2 functions as a pioneer factor and will serve as prelude for therapeutic initiatives to engineer and promote regeneration of the cardiovascular lineages. Given the tremendous morbidity and mortality of cardiovascular disease in our society, the potential impact of this proposal is significant.

Cardiovascular disease is common and contributes to the morbidity and mortality of our patients. The longterm goal and the clinical significance of this proposal are to define the initial factors that govern the stem cell/progenitors to promote the formation of new vessels in response to injury or disease. The results from these studies will serve as an important platform for therapeutic initiatives focused on cardiovascular disease.