Murine fumarylacetoacetate hydrolase (Fah) gene is disrupted by a neonatally lethal albino deletion that defines the hepatocyte-specific developmental regulation 1 (hsdr-1) locus.

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Homozygous deletion of the hepatocyte-specific developmental regulation 1 (hsdr-1) locus in mouse chromosome 7 results in perinatal death and a pleiotropic syndrome characterized by ultrastructural abnormalities of the liver and kidney, failure of induction of a number of specific transcription units in the liver and kidney during late gestation, and marked overexpression of an enzyme that defends against oxidative stress. Previously, the breakpoints of two albino (c) deletions (c14CoS and c1FAFyh) that genetically define hsdr-1 were localized, on a long-range map, in the vicinity of the distal breakpoint of a viable albino deletion (c24R75M) that breaks proximally within the c locus. Here we report the use of a probe derived from a deletion breakpoint fusion fragment cloned from c24R75M/c24R75M DNA to clone a breakpoint fusion fragment caused by the c14CoS deletion. The proximal breakpoint of the c14CoS deletion was discovered to disrupt a gene (Fah) encoding fumarylacetoacetate hydrolase, the last enzyme in the tyrosine degradation pathway. All of the extant c deletions eliciting the hsdr-1 phenotype prevent expression of the Fah gene in the liver, and all but one disrupt the coding segment of the gene. Therefore, the Fah gene maps within or proximal to the hsdr-1 locus, as defined by deletion breakpoints, and disruption of this gene may be partially or completely responsible for the phenotypes associated with the hsdr-1 deletion syndrome. These mouse mutants may also provide models for the human genetic disorder hereditary tyrosinemia, which is associated with fumarylacetoacetate hydrolase deficiency and liver and kidney dysfunction.

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