Oxygen free radical damage has been implicated in nearly every aspect of human development and disease. The role of Cu/Zn superoxide dismutase (SOD-1) an oxygen free radical scavenging enzyme, in preventing such damage has been intensively studied. Our laboratory has recently cloned the genomic sequence for murine SOD-1, and identified a processed pseudogene of this enzyme. We will use the genomic clone to conduct definitive experiments on the role of oxygen free radicals in abnormal mouse development. To attain this goal, we will perform insertional disruption of the SOD-1 gene in mice by targeted mutagenesis in embryonic stem (ES) cells, thereby to produce mice with either 50% of the normal activity of SOD-1, no activity at all. Such animals should have broad applicability to studies of aging, environmental toxicology and teratology. In this proposal we focus our attention on teratology; specifically, on the fetal alcohol syndrome (FAS). FAS, a major preventable cause of mental retardation in humans, can be mimicked in mice, and oxygen free radicals have been implicated though not proven to be mediators of ethanol (EtOH) teratogenicity. Further, the role of maternal versus fetal genotype in FAS susceptibility has not been clearly separated. By deleting the SOD-1 gene in an inbred mouse strain, we can both test the role of oxygen free radicals in FAS, and at the same time distinguish effects of maternal and fetal genotype on susceptibility. Females carrying a deletion of SOD-1, when mated to normal males, will gestate fetuses, half of which will be genetically wild type, and half of which will be SOD-1 deletion carriers with 50% the normal level of SOD-1 activity. These fetuses can be studied for ethanol-induced teratogenic effects and subsequently analyzed for their SOD-1 genotype. Similarly, normal females mated to males heterozygous for the deletion will provide a normal maternal environment to the genetically distinct fetuses. Finally, if mice homozygous for the SOD-1 deletion are viable, these can be studied for increased sensitivity to EtOH using similar mating and/or embryo transfer protocols. We will also investigate whether insertion of new SOD-1 genes by pronuclear microinjection can confer resistance to EtOH teratogenicity. These studies should provide new insights into FAS, and establish a valuable new animal model for mammalian teratology. We also will study the evolution of this important enzyme by sequencing and mapping the pseudogene.
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