The goal of this project is to investigate coronary vascular emergence in an important biomedical model of developmental disease. The zebrafish has contributed significantly to the understanding of developmental biological process, including cardiac development. At the present time, neither the timing of the appearance of the first coronaries in the zebrafish, nor the sources of the cells that contribute to its developing myocardial coronary plexus is known. Here we seek 1) to determine the spatiotemporal characteristics of coronary vessels development, 2) to identify a set of embryonic endocardial progenitor cells that contributes to its emergence, and 3) to ascertain whether these cells have import on coronary regeneration in the setting of injury. First, the spatiotemporal aspects of coronary development in the zebrafish will be accomplished by a combination of parallel approaches including the imaging of vascular-specific labeled fluorescent transgenics, light microscopic imaging of plastic sections and the use of focused ion beam- scanning electron microscopy (FIB-SEM), a powerful and novel approach that will provide ultrastructural three dimensional information about the developing heart. Second, we will determine whether the embryonic endocardium and a subset of Gata4-labeled endocardial cells in particular contribute to the developing coronary vasculature. Third, we will test the potential of endocardial cells in regenerative processes in the zebrafish heart. The new knowledge gained may lead to better understanding of human coronary development and coronary revascularization. Importantly, this project will be carried out principally at an undergraduate institution with a strong tradition of faculty-student research collaborations, and a PI with a strong record of undergraduate primary and co-authorship of published papers. Undergraduate students exposed to highly meritorious research, will be mentored and will contribute to an important area of developmental biomedical science. The PI offers a tradition of undergraduate students from his lab pursuing graduate degrees in biomedical sciences. Funding of this proposal will also strengthen research infrastructure at DePauw University and enhance the opportunities for continued undergraduate student interest in biomedical research.