THE GENES ENCODING GONADAL AND NONGONADAL FORMS OF 3-BETA-HYDROXYSTEROID DEHYDROGENASE/DELTA(5)-DELTA(4) ISOMERASE ARE CLOSELY LINKED ON MOUSE CHROMOSOME-3

The biosynthesis of steroid hormones in the gonads and adrenal glands requires the activities of the enzyme 3β-hydroxysteroid dehydrogenase/isomerase (3βHSD) which catalyzes the NAD<-dependent dehydrogenation and subsequent Δ5 → Δ4 isomerization of Δ5-3β-hydroxysteroids to Δ4-3-ketosteroids. The mouse expresses four isoforms of 3βHSD. 3βHSD I is expressed in gonads and adrenal glands and appears to be the major steroidogenic form, 3βHSDs II and III are expressed in both liver and kidneys, and 3βHSD IV has been detected only in kidneys. To determine the genetic relationship between the 3βHSD isoforms, we have mapped the chromosomal locations of the four genes by linkage analysis using gene-specific probes derived from the 3′ untranslated regions of 3βHSD cDNA clones. The four 3βHSD 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 ± 2.2)-Hsd3b-(3.3 ± 1.9)-Tshb-(6.7 ± 2.7)-Amy-1. © 1993 Academic Press, Inc.