Steroid enzyme gene expressions during natural and androgen-induced gonadal differentiation in the rainbow trout,Oncorhynchus mykiss

✍ Scribed by Govoroun, Marina ;McMeel, Oonagh Marie ;D?Cotta, Helena ;Ricordel, Marie-Jos� ;Smith, Terry ;Fostier, Alexis ;Guiguen, Yann

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 318 KB
• Volume: 290
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1106

✦ Synopsis

Abstract

In fish, according to Yamamoto’s model, androgens would drive testis differentiation and estrogens ovarian differentiation. In order to study the implication of steroid enzymes in rainbow trout gonadal differentiation, we examined the expression of some steroid enzyme genes during natural differentiation (cholesterol side chain cleavage = P450scc, 17‐hydroxylase/lyase = P450c17, 3β‐hydroxysteroid dehydrogenase = 3βHSD) and androgen‐induced differentiation (P450scc, P450c17 , 3βHSD, aromatase = P450aro, and 11β‐hydroxylase = P45011β). Expressions of P450scc, 3βHSD, and P450c17 were all detected in male and female gonads at 55 days post‐fertilization (dpf), i.e., two weeks before histological differentiation. There were no differences in their expression level respective to the sex. The androgen treatment was carried out by administration of 11β‐hydroxyandrostenedione (11βOHΔ4) in genetic all‐female populations and the resulting sex ratios were found to be 100% male even at a low dosage of 1 mg/kg of food. Following 11βOHΔ4 treatment, only the expression of P450c17 was found to be sustained when compared with the female untreated control. In contrast, P450scc was clearly up‐regulated and 3βHSD and P450aro down‐regulated by the androgen treatment. P45011β gene expression remained low in gonads of androgen‐treated females, as it did in control untreated females. These results together demonstrate that steroidogenesis in rainbow trout is potentially active in pre‐differentiating gonads of both sexes, and that one of the masculinizing actions of androgens in the species may be to down‐regulate the female‐specific gonadal P450aro gene expression. However, in vivo androgen treatment in genetic females does not induce the same pattern of steroid gene expression as in genetic males. These data suggest that exogenous androgens might induce a male differentiation process with P450aro inhibition being one of the steps required. However, this process would not involve endogenously produced 11‐oxygenated androgens. J. Exp. Zool. 290:558–566, 2001. © 2001 Wiley‐Liss, Inc.