Regulatory genes linked to the albino locus in the mouse confer competence for inducible expression on the structural gene encoding serine dehydratase

Extrahepatic expression of NAD(P)H:menadione oxidoreductase, UDP glucuronosyltransferase-1A6, microsomal aldehyde dehydrogenase, and hepatic nuclear factor-1 alpha mRNAs in ch/ch and 14CoS/14CoS mice

Oxidative stress-induced gene expression in liver of the untreated newborn c14CoS/c14CoS mouse, as compared with that in the cch/cch wild-type mouse, appears to be caused by homozygous loss of the fumarylacetoacetate hydrolase (Fah) gene on Chr 7 and absence of the FAH enzyme, which leads to increased levels of endogenous reactive oxygenated metabolites (ROMs) formed in the tyrosine degradative pathway. In these mice almost all studies to date have been carried out in liver. We have examined the extrahepatic expression of four genes. Two genes are members of the [Ah] battery and induced by ROM-mediated oxidative stress: NAD(P)H:menadione oxidoreductase (Nmo1) and UDP glucuronosyltransferase-1A6 (Ugt1a6). The other two genes are decreased in the livers of 14CoS/ 14CoS mice as compared with that in ch/ch mice: microsomal aldehyde dehydrogenase (Ahd3) and hepatocyte-specific nuclear factor-1 alpha HNF-1 alpha (Hnf1 alpha). In liver plus nine extrahepatic tissues of untreated newborn 14CoS/14CoS mutant and ch/ch wild-type mice, we compared NMO1, UGT1A6, AHD3 and HNF-1 alpha mRNA levels. Our results show a wide variation in extrahepatic tissue-specific expression of all four transcripts and indicate that numerous differences exist in the extrahepatic expression of these genes between 14CoS/14CoS and ch/ch mice.

Chromosomal deletions around the albino locus in the mouse cause loss of hormone-inducible expression of the unlinked structural gene encoding cytosolic aspartate aminotransferase

A group of genes in the mouse encoding liver-specific gluconeogenic enzymes and mapping on different chromosomes lose their normal competence for hormone-inducible expression in animals homozygous for chromosomal deletions around the albino locus on chromosome 7. The basal expression of these same genes remains normal. In previous investigations, glucocorticoid hormones as well as their receptors were found to be normal in the deletion homozygotes. The results reported here identify an additional unlinked structural gene whose regulation appears to be affected by the deletions--i.e., that encoding cytosolic aspartate aminotransferase, a housekeeping gene that participates in gluconeogenesis in the liver. In normal mice, its mRNA level increases sharply at birth, specifically in the liver, and can be increased even further by dexamethasone and cAMP treatment. These increases fail to occur in mice homozygous for the specific deletions in chromosome 7. Interestingly, prenatally at 18-19 days of gestation, the gene is expressed at the same basal level in liver and brain of both normal and mutant mice. These observations strengthen the evidence implicating the deleted gene(s) as an essential factor(s) in the normal mechanisms of hormone-inducible expression of particular unlinked structural genes.