The Molecular Mechanism For VEGFA In Regulating Cardiovascular Development

Congenital heart disease（CHD）is a common birth defect caused by abnormal embryonic development.Left ventricular outflow tract obstruction（LVOTO）malformation is a subset of CHD,comprise a spectrum of stenotic lesions from left ventricular outflow to descending aortic arch.LVOTO contains a series of malformation of ventricle,vavle and outflow tract.These lesions may present in concert indicating a common genetic mechanism for LVOTO.Since vascular endothelial growth factor A（VEGFA）regulates both vasculogensis/angiogensis and heart development,we speculate that VEGFA may associate with LVOTO.In our clinical work previously,we found two mutations of VEGFA among LVOTO patients（c.973C>T and c.998 G>A）.To further study function of VEGFA in development,we apply zebrafish as an animal model to knock down vegfaa and vegfab,which are homologous to VEGFA in human.Vegfaa morphants show defects in heart and vessel development while vegfab morphants are normal at early stage.Next,we use transcription activator-like effector nuclease（TALEN）to establish a mutant line of vegfaa.Homozygous loss of vegfaa is embryonic lethality and heterozygous mutants can survive to adulthood.Vegfaa^-/-shows defects in differentiation of dorsal aorta and posterior cardinal vein accompanying unregulated and delayed intersegmental vessel sprouting.In brain,vegfaa^-/-cannot form lateral dorsal aorta by flk⁺endothelial cells unregulated distribution.For heart development,vegfaa^-/-has decreased myocardium in both atrium and ventricle and loss of endothelial mesenchymal transition（EMT）resulting in valve missing.Bmp4 and Wnt-βcatenin are overexpressed and ectopic expression in vegfaa^-/-indicating VEGFA/bmp/Wnt-βcatenin pathways crosstalk in regulating cardiovascular development.