Analyses of Molecular Characteristics and Enzymatic Activities of Ovine HSD17B3

SIMPLE SUMMARY: Mutations of 17β-hydroxysteroid dehydrogenase type3 (HSD17B3) gene cause disorder of sex differentiation (DSD). In this study, the open reading frame sequence of ovine HSD17B3 was revealed, and the effects of amino acid substitution on ovine and human HSD17B3 enzymatic activities were evaluated. Although ovine HSD17B3 has a conserved amino acid sequence, it possesses two amino acid substitutions that are consistent with the reported variants of human HSD17B3. Substitution of these amino acids in ovine HSD17B3 for those in human did not affect the enzymatic activities. Similarly, substitution of these amino acids of human HSD17B3 for those in ovine also did not affect the enzymatic activities. However, enzymatic activities declined in the missense mutations of the HSD17B3 gene associated with DSD, which occurred in the conserved amino acids between both species. ABSTRACT: 17β-hydroxysteroid dehydrogenase type 3 (HSD17B3) converts androstenedione (A4) into testosterone (T), which regulates sex steroid production. Because various mutations of the HSD17B3 gene cause disorder of sex differentiation (DSD) in multiple mammalian species, it is very important to reveal the molecular characteristics of this gene in various species. Here, we revealed the open reading frame of the ovine HSD17B3 gene. Enzymatic activities of ovine HSD17B3 and HSD17B1 for converting A4 to T were detected using ovine androgen receptor-mediated transactivation in reporter assays. Although HSD17B3 also converted estrone to estradiol, this activity was much weaker than those of HSD17B1. Although ovine HSD17B3 has an amino acid sequence that is conserved compared with other mammalian species, it possesses two amino acid substitutions that are consistent with the reported variants of human HSD17B3. Substitutions of these amino acids in ovine HSD17B3 for those in human did not affect the enzymatic activities. However, enzymatic activities declined upon missense mutations of the HSD17B3 gene associated with 46,XY DSD, affecting amino acids that are conserved between these two species. The present study provides basic information and tools to investigate the molecular mechanisms behind DSD not only in ovine, but also in various mammalian species.