Congenital malformations of the heart have been reported following maternal exposure to various environmental toxins, but the precise mechanism(s) by which these teratogenic exposures disrupt normal morphogenesis remains unknown. Prenatal exposure to ethanol (Fetal Alcohol Syndrome) or maternal vitamin A (retinoic acid) deficiency or excess during gestation have been shown to cause conotruncal heart defects. In the proposed research program, the complex processes underlying embryological development of the mammalian heart and the impact of prenatal exposure to ethanol and perturbed retinoic acid levels leading to cardiac dysmorphogenesis will be studied using molecular-genetic approaches. The proposed studies will focus on a critical gestational timepoint during murine heart development when the cardiac neural crest cells are migrating from the dorsal neural tube to the heart. Alterations in the network of developmentally regulated genes in this cell population will be analyzed following teratogen exposure through the use of genetic microarrays. Potential mechanisms suggested by altered gene expression profiles will be further evaluated relative to the observed cellular dysmorphology by examining protein expression of critical candidate genes identified in the cDNA arrays, as well as proteins associated with changes in cell proliferation and apoptosis. The goal will be to identify significant gene/protein interactions that take place during normal heart development, and the mechanism(s) by which in utero ethanol exposure disrupts this process. We will also further investigate the possibility that malformations of the heart subsequent to prenatal alcohol exposure are a result of decreased endogenous retinoic acid synthesis due to competition between alcohol and retinol for alcohol dehydrogenase enzymatic pathways. The proposed research program will therefore test the hypothesis that prenatal ethanol exposure leads to congenital heart malformations by disrupting normal retinoid signaling pathways critical for cell fate determination in the migrating cardiac neural crest cells/conotruncus.
