PROJECT SUMMARY/ABSTRACT Congenital Heart Disease (CHD) is the most common birth defect affecting approximately 1% of all live births in the US and is one of the leading causes of infant mortality. A severe form of CHD can result from heterotaxy, a disorder of Left-Right (LR) patterning, during embryonic development. A recent genetic analysis of heterotaxy patients identified a novel CHD candidate gene, LRPPRC. LRPPRC encodes a mitochondrial mRNA stabilizer which is critical for oxidative (aerobic) metabolism in the mitochondria. However, it has no known role in LR patterning or embryonic development. Using different knockdown/knockout strategies in the high-throughput hu- man disease model, Xenopus, loss of lrpprc leads to LR patterning defects that recapitulate the patient’s phenotype. The overall goal of this proposal is to investigate the molecular mechanism by which lrpprc affects LR patterning and heart development in the Xenopus (frog) model system and determine how its role in mitochondrial metabolism relates to the regulation of early embryonic development. The first aim will determine the required role of lrpprc during embryonic patterning by using loss of function experiments to assess changes in left-right and dorsal-ventral patterning markers during the LR patterning cascade and earlier, at gastrulation. The second aim will investigate the mechanism by which lrpprc regulates embryonic patterning;; specifically, experiments will determine if the protein’s known mitochondrial function is important for its role in LR patterning and cardiac development. By attempting to phenocopy left-right and dorsal-ventral patterning de- fects through knockdown of other key OXPHOS regulatory proteins, performing real-time analysis of O2 consumption (oxidative metabolism) and glycolysis during key developmental events, and confirming that Lrpprc is required in the mitochondria during early development, experiments in this aim will better defining the relation- ships between lrpprc, metabolism, and early embryonic patterning and development. Altogether, this project will improve our understanding of cardiac development and the role of lrpprc and mitochondrial metabolism in the pathogenesis of CHD. In the future, this will benefit genetic testing and counseling, as well as improve outcomes in CHD because treatments can be tailored to genotype rather than solely on CHD phenotype. In addition, this application details the applicant’s training plan including research mentorship, advanced coursework, training in new techniques, and the development of skills in scientific professionalism, writing, and presentation of data. The research and training outlined in this application will prepare the applicant to pursue a career performing patient-driven research as an independent research scientist.