Prenatal ethanol exposure is the leading known cause of mental retardation. Growing evidence suggests that excessive cell death is a major component of the pathogenesis of ethanol-induced birth defects. However, there is a fundamental gap in understanding how ethanol leads to apoptotic cell death in embryos. Continued existence of this gap represents an important problem because, until it is filled, understanding of ethanol- induced apoptosis that leads to teratogenesis will remain largely incomprehensible. Our long-term goal is directed toward the development of effective strategies against ethanol's teratogenesis; strategies based on prevention of ethanol-induced apoptosis through targeting specific proteins involved in apoptosis. The overall objective of this particular proposal is to establish Siah1, a member of the seven in absentia homology family, as a feasible target for the prevention of ethanol-induced apoptosis and teratogenesis. The central hypothesis to be tested is that Siah1 mediates ethanol-induced apoptosis in neural crest cells (NCCs) by activating the p53 pathway and that the inhibition of Siah1-mediated apoptosis can prevent ethanol-induced teratogenesis. Our hypothesis has been formulated on the basis of strong preliminary data produced in our laboratory. To test our hypothesis, the following specific aims will be addressed: Aim1: To characterize the role of Siah1 in ethanol-induced apoptosis in NCCs. We will determine the effects of ethanol on Siah1 mRNA and protein expression, and investigate the potential of ethanol to promote Siah1 nuclear translocation and induce apoptosis. Aim2: To test the hypothesis that Siah1 mediates ethanol-induced apoptosis in NCCs by activating the p53 pathway. This will be accomplished by determining the role of Siah1 in ethanol-induced activation of p53 signaling pathway and in the induction of p53 downstream proapoptotic proteins and apoptosis. Aim3: To define the role of the inhibition of Siah1 function in conferring protection against ethanol-induced teratogenesis. This will be accomplished by using whole embryo culture, Siah1 knockout mice and an oral intake FASD model. We will determine whether knocking down Siah1 diminishes ethanol-induced malformations in cultured mouse embryos and whether Siah1 deficiency in Siah1-/- mouse embryos can confer in vivo protection against ethanol-induced teratogenesis. The proposed work is innovative, because it focuses on a novel approach, targeting specific proteins directly involved in the apoptotic pathway, to preventing ethanol-induced apoptosis and teratogenesis. The theoretical concept described in the application is also highly innovative because this is the first study attempting to prevent ethanol-induced apoptosis and teratogenesis specifically through the newly recognized actions of Siah1 in apoptosis. The results from this study will be significant, because the insights gained by the accomplishment of these aims will help in elucidating the role of Siah1 in mediating ethanol- induced teratogenesis. They are also expected to yield strategies for the prevention of ethanol's teratogenesis and to fundamentally advance the field of FASD research.