The Second Heart Field in Lymphovenous Valve Development: Understanding Lymphatic Dysfunction in Congenital Heart Disease - PROJECT SUMMARY As the most common birth defect, congenital heart disease (CHD) is a prevalent health concern. Some of the most severe and life-threatening CHD arise in the arterial pole, where a subpopulation of mesodermal progenitors called the second heart field (SHF) contribute to the myocardium of the outflow tract and right ventricle. Children with CHD are prone to debilitating lymphatic conditions including plastic bronchitis, lymphedema, chylothorax, and protein-losing enteropathy. However, insufficient research into the lymphatic system in the context of CHD has been conducted. To determine the basis of lymphatic dysfunction in patients with CHD, I focus on understanding the development of the bilateral bicuspid lymphovenous valves (LVVs), through which interstitial fluid collected by lymphatics drains into the venous circulation. LVVs are necessary gatekeepers at the junction of lymphatic ducts with veins and their absence results in primary lymphedema and blood-filled lymphatics. Our preliminary data suggest that the SHF contributes not only to cardiomyocytes but also to LVVs. I expect this work will establish the SHF as a common precursor of the lymphatic and cardiovascular systems. Through my specific aims, I plan to determine 1) when SHF-derived cells contribute to developing LVVs and if they do so through a venous intermediate and 2) if this contribution is required for proper LVV formation. In my first aim, I will use constitutive and inducible Cre-loxP technology, intersectional fate mapping, and immunofluorescence staining of mouse embryos to genetically trace SHF cell lineage and fate map SHF progenitors. In my second aim, I will utilize conditional knockout mouse models and immunofluorescence staining to determine if SHF progenitors are required for LVV development. I will investigate if defects in the SHF precipitate abnormal LVV development in a mouse model of the human disease 22q11DS, which presents clinically as SHF-related heart defects and can be accompanied by lymphedema. Completion of the studies described in this proposal will provide novel insight into the development of lymphatics, the cellular origin of the LVVs, and lymphatic defects in CHD patients. My findings will lead to improved screening and treatment of potentially life-threatening lymphatic defects in CHD patients. The proposed project will be carried out in a well-equipped laboratory at Rutgers New Jersey Medical School, guided by a sponsor with a strong record of research contributions to vascular development in the context of congenital heart disease. The sponsor has mentored numerous graduate students to success and brings a wealth of experience to the project. The PI will utilize her previous training in developmental biology, supplemented by new skills in lineage tracing and quantitative analysis of three-dimensional confocal datasets. Her training plan outlines achievable objectives in field-specific research training, dissemination of findings, clinical experience, mentoring, and professional development.
