Cloning and chromosomal localization of mouse 20α-hydroxysteroid dehydrogenase gene

20alpha-hydroxysteroid dehydrogenase (20alpha-HSD), a member of the aldo-keto reductase (AKR) superfamily, metabolizes progesterone to its inactive form, 20alpha-dihydroprogesterone (20alpha-OHP). 20alpha-HSD is associated with functional luteolysis and plays a significant role in the reproductive system of rodents. Here we report cloning and determination of the chromosomal location of the mouse 20alpha-HSD gene. The mouse 20alpha-HSD gene cloned using 129 SvJ mouse genomic library spanned approximately 18 kb from exon 1 to exon 9. A single transcription start site was identified by 5'-rapid amplification of cDNA ends (RACE) at the site of 50 nucleotides upstream from the ATG translation initiation codon. The exon-intron organization of mouse and human 20alpha-HSD genes were similar. Using 17.5 kb of genomic clone as a probe, we determined the chromosomal location by fluorescence in situ hybridization (FISH). The chromosome in which the mouse 20a-HSD gene was detected was identified as chromosome (Chr) 13 according to simultaneous G- and R-banding. Because type 5 17beta-HSD gene, a member of the AKR superfamily, is also located on Chr 13, the present result supports the syntenic relationship between mouse Chr 13 and human Chr 10, which was previously suggested at the chromosomal loci of a gene cluster of the AKR superfamily.