THE HUMAN 3-BETA-HYDROXYSTEROID DEHYDROGENASE (3-BETA-HSD) GENE-CLUSTER ON CHROMOSOME 1P13 CONTAINS A PRESUMPTIVE PSEUDOGENE - 3-BETA-HSD AND CYP17 DO NOT SEGREGATE WITH DOMINANTLY INHERITED HIRSUTISM

Four hirsute females from a family exhibiting idiopathic dominant hirs utism were examined. Basal blood levels of Delta(5) and Delta(4) stero ids were within the normal range, but ACTH stimulation led to increase s in 17-hydroxypregnenolone and dehydroepiandrosterone that were signi ficantly above control levels. Using polymorphic genetic markers, the genes for cytochrome P450c17 encoded by CYP17, and the type I and II f orms of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) were found no t to segregate with hirsutism in this family, though a base substituti on was detected in the 3' end of exon 1 of the gene for 3 beta-HSD typ e I in three of the four patients investigated. Analysis of PCR amplif ication products by denaturing gradient gel electrophoresis (DGGE) and sequencing revealed a novel homologue of exon 3 of 3 beta-HSD. DNA of one of the affected patients was used to create a genomic library in lambda gem11 and clones containing the novel homologue were obtained a nd partially sequenced. The equivalent clone was obtained from a genom ic library of an unrelated normal individual. The sequences of the clo nes from patient and control were identical and homologous to exons 2- 4 of human 3 beta-HSD types I and II. No difference was found in the P CR primer sites that flanked the exon 3 homologue which led to its det ection on DGGE gels. In both clones, stop codons and deletions were id entified in the exon 4 homologue, leading to the deduction that the se quence comes from a pseudogene, which we call 3 beta-HSD psi 1. The ps eudogene mapped to chromosome 1p13. It was concluded that dominantly i nherited idiopathic hirsutism in this rare kindred was not due to defi ciencies in 3 beta-HSD types I, II, or psi, or of CYP17.