Intrauterine ethanol (ETOH) exposure is a common cause of congenital mental retardation. The mechanism of varying susceptibility of exposed offspring may include genetic-or environmentally-induced variation in ETOH metabolizing enzymes. The PI has shown that the alcohol dehydrogenase 2*3 allele (ADH2*3), unique to African Americans and associated with increased ETOH metabolism, is protective against adverse offspring outcome after intrauterine ETOH exposure. A role for CYP2E1 in alcohol related birth defects (ARBD) is supported by the enzyme's activity at high ETOH concentrations, its presence in areas of the brain affected in intrauterine exposure and its inducibility by ETOH intake. The PI recently found a restriction fragment length polymorphism (RFLP) in the regulatory region of human CYP2E1 that correlates with increased in vivo CYP2E1 activity in the presence of obesity or ETOH intake. The RFLP occurs in about 30 percent of African Americans and 10 percent of Caucasians. We propose to assess the mutation as a risk factor for ARBD, as well as the mechanism whereby the mutation alters CYP2E1 expression. We will test the hypothesis that, controlling for ETOH intake and ADH2 genotype, the mutation correlates with better offspring outcome. This study is both time- and cost-effective because previously collected data and blood samples will be used. Available data includes ETOH intake during pregnancy, maternal and offspring ADH genotype and offspring outcome at birth and 1 year of age. These results will further define those at greatest risk for ARBD; however, utilizing this information for intervention will require an understanding of the molecular mechanism. We will test the hypotheses that the RFLP is an insertion mutation that affects CYP2E1 transcription by either disruption of a negative regulatory element or by insertion of a positive regulatory element. The precise sequence and location of the mutation will be defined. The ability of the mutation to alter gene expression will be tested by comparing the ability of wild type and mutated sequences to direct the transcription of a reporter gene in the presence and absence of potential mediators. Electrophoretic mobility shift assays will test the effect of the mutation on the binding of trans-acting regulatory elements and may allow determination of the involved transcription factors. Understanding the mechanisms and underlying molecular basis for ARBD is the first step in planning future intervention, as well as targeted prevention protocols. The results of these studies also will have application to multiple diseases in which CYP2E1-mediated xenobiotic activation occurs and for which ETOH intake and CYP2E1 induction may alter risk.
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