Molecular cloning and characterization of estrogen and androgen receptors in Mandarin fish, Siniperca chuatsi

Abstract Steroid hormones are essential for the normal reproductive activity in females and males, such as early sex differentiation, gonad development and sex reversal, which works by binding with the steroid receptors. In the present study, the full-length of estrogen receptors (ERα, ERβ1 and ERβ2) and androgen receptors (ARα and ARβ) cDNAs were isolated from the mandarin fish (Siniperca chuatsi). Real time quantitative PCR (RT-qPCR) revealed that ERα and ERβ2 expressed mainly in the liver of females and males, and ERβ1 mostly distributed in ovary and testis. Additionally, the high expressions of ARα and ARβ in both females and males were detected in gonads and livers respectively. During the early sex differentiation stage, the expressions of ERs and ARs in female were higher than in male during 5–30 day after hatching (dah), and reached the peak level at 30 dah. In males, the expressions of ERβ1, ERβ2, and ARβ increased largely during 30 dah to 60 dah, and revealed significantly higher levels than in females during 60–180 dah. In female, the expression of ERβ2 in ovary increased sharply at 180 dah. Moreover, the result of gonadal histology revealed that the spermatocytes were observed at 45 dah and the spermatozoon could be found largely at 60 dah in males and oil droplets appeared for the first time in the oocytes at 180 dah. The expression levels of three ERs and ARβ were up-regulated and the ARα was down-regulated during female to male sex reversal induced by 17α-methyltestosterone (MT). Furthermore, after MT treatment for 30 and 35 days, the expressions of ERβ1, ERβ2 and ARβ were significantly up-regulated. These results suggest that ERβ1, ERβ2 and ARβ may play critical roles in spermatogenesis and masculinization, while ERβ2 and ERβ1 may be essential for vitellogenesis and ovary development in female.