Expression and Regulation of Fushi Tarazu Factor-1 and Steroidogenic Genes During Reproduction in Arctic Char (Salvelinus alpinus)1

Abstract

Teleost fushi tarazu factor-1 (FTZ-F1) is a potential regulator of steroidogenesis. The present study shows sex-specific regulation of Arctic char fushi tarazu factor-1 (acFF1) and steroidogenic genes during reproductive maturation and in response to hormone treatment. A link between gonadal expression of acFF1, steroidogenic acute regulatory protein (StAR), and cytochrome P450-11A (CYP11A), was observed in the reproductive maturation process, as elevated acFF1 mRNA and protein levels preceded increased StAR and CYP11A transcription. Sex-specific differences were observed as estrogen treatment resulted in down-regulated levels of acFF1 mRNA in testis and male head kidney, whereas no significant effect was observed in females. 11-Ketotestosterone (11-KT) down-regulated CYP11A and 3beta-hydroxysteroid dehydrogenase (3betaHSD) in head kidney and up-regulated CYP11A in testis. StAR remained unaffected by hormone treatment. This suggests that acFF1 is controlled by 17beta-estradiol, whereas the effects on CYP11A and 3betaHSD are mediated by 11-KT. Coexpression of acFF1, StAR, and CYP11A was observed in head kidney, in addition to gonads, indicating correlation between these steroidogenic genes. StAR and acFF1 were also coexpressed in liver, suggesting a potential role in cholesterol metabolism. Although these results indicate conserved steroidogenic functions for FTZ-F1 among vertebrates, they also raise the question of additional roles for FTZ-F1 in teleosts.