Two steroid 15 alpha-hydroxylase genes and a homologous gene family in mice

Steroid 15 alpha-hydroxylase (P45015 alpha) activity is concomitant with the expression of two types of mRNA in the mouse liver. Two discrete genes, designated 15 alpha oh-1 and 15 alpha oh-2, that encode the two mRNAs were recovered from total genomic libraries of the inbred mouse strains 129/J and C57Bl/6J and identified by cDNA hybridization, restriction-site analysis and partial nucleotide sequence. Both genes are approx. 9 kb long and share significant homology, including flanking regions, over a region of at least 30 kb. The two distinct 15 alpha oh genes are members of a larger family of homologous genes and/or pseudogenes of unknown function. The most extensive sequence homology among family members in the 3' portion of the gene with progressively less homology toward the 5' end. The far 5' portions of 15 alpha oh-1 and 15 alpha oh-2 are very similar to one another but there is no observed homology with other genes of the family. The two 15 alpha oh genes and the homologous family have been localized to mouse chromosome 7 by somatic cell hybrid mapping. Analysis of a restriction fragment length polymorphism in recombinant inbred mice shows a close linkage of 15 alpha oh-1 and 15 alpha oh-2 with the Coh locus.