Tissue-specific expression and chromosomal location of the 3beta-hydroxysteroid dehydrogenase gene family of the mouse.

The biosynthesis of steroid hormones in the gonads and adrenal glands requires the activities of the enzyme 3$\beta$-hydroxysteroid dehydrogenase/isomerase (3$\beta$HSD) which catalyzes the NAD$\sp+$-dependent dehydrogenation and subsequent $\Delta\sp5\to\Delta\sp4$ isomerization of $\Delta\sp5$-3$\beta$-hydroxysteroids to $\Delta\sp4$-3-ketosteroids. Four forms of 3$\beta$HSD have been characterized in the mouse that share significant identity, but differ from each other by 5-25% within their coding regions. RNA that hybridizes to radiolabeled 3$\beta$HSD probes is present in the gonads, adrenal glands, liver and kidney of both sexes. RNase protection analysis using antisense probes derived from each of the three forms demonstrates that one form, 3$\beta$HSD I, is restricted to the gonads and adrenal glands. Two other forms, 3$\beta$HSD II and III, are expressed in liver and kidney but are not detected in steroidogenic tissues. The fourth form, 3$\beta$HSD IV, has been detected only in kidneys. A polyclonal antibody raised against the human placental form of 3$\beta$HSD recognizes a 42 kDa protein in gonadal and adrenal tissue and a 45 kDa protein in liver. The antibody weakly recognizes a 42 kDa protein in kidney. 3$\beta$HSD enzyme activity is present in testicular, adrenal, hepatic and renal tissue, with adrenal tissue possessing the highest specific activity. When expressed as total 3$\beta$HSD activity for whole organ mass, activity is greatest in the liver. To determine the genetic relationship between the 3$\beta$HSD isoforms, we have mapped the chromosomal location of the four genes by linkage analysis using gene-specific probes derived from the 3$\sp\prime$ untranslated regions of 3$\beta$HSD cDNA clones. The four 3$\beta$HSD structural genes (Hsd3b) are closely linked within a segment of chromosome 3 that is conserved on human chromosome 1. The order of markers on Chr 3 surrounding Hsd3b is: centromere--Gba--(4.4 $\pm$ 2.2)--Hsd3b--(3.3 $\pm$ 1.9)--Tshb--(6.7 $\pm$ 2.7)--Amy-1. The four genes are present on a single 400 kb Ksp I fragment, suggesting that the 3$\beta$HSD gene family is arranged as a cluster of related genes which may have arisen through tandem duplication of a single ancestral gene.PhDCellular and Molecular BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103706/1/9409629.pdfDescription of 9409629.pdf : Restricted to UM users only