Gene Expression ofTakifugu rubripesGonads During AI- or MT-induced Masculinization and E2-induced Feminization

Abstract

Elucidating the global molecular changes that occur during aromatase inhibitor (AI)- or 17α-methyltestosterone (MT)-induced masculinization and estrodiol-17β (E2)-induced feminization is critical to understanding the roles that endocrine and genetic factors play in regulating the process of sex differentiation in fish. Here, fugu larvae were treated with AI (letrozole), MT, or E2 from 25 to 80 days after hatching (dah), and gonadal transcriptomic analysis at 80 dah was performed. The expression of dmrt1, gsdf, foxl2, and other key genes (star, hsd3b1, cyp11c1, cyp19a1a, etc.) involved in the steroid hormone biosynthesis pathway were found be altered. The expression of dmrt1, gsdf, cyp19a1a, and foxl2 was further verified by qPCR. In the control group, the expression of dmrt1 and gsdf was significantly higher in XY larvae compared to XX larvae, while the expression of foxl2 and cyp19a1a was significantly higher in XX larvae compared to XY larvae (p < 0.05). AI treatment suppressed the expression of foxl2 and cyp19a1a, and induced the expression of dmrt1 and gsdf in XX larvae. MT treatment suppressed the expression of foxl2, cyp19a1a, dmrt1, and gsdf in XX larvae. E2 treatment suppressed the expression of dmrt1 and gsdf, but did not restore the expression of foxl2 and cyp19a1a in XY larvae. The shared response following AI, MT, and E2 treatment suggested that these genes are essential for sex differentiation. This finding offers some insight into AI or MT-induced masculinization, and E2-induced femininization in fugu.

Profile of gene expression changes during estrodiol-17β-induced feminization in the Takifugu rubripes brain

“…Figure 1 shows the results of the histological analysis of the gonads. As reported by Yan et al, sex reversed larvae were not observed in the control groups [ 22 ]. Gonads from the C-XX group occupied the ovarian cavities, which were filled with a small number of oocytes and a large number of oogonia, closely arranged on the oviposition plate.…”

“…In T. rubripes , previous studies have also found that treatment with E 2 , during early sex differentiation, can induce feminization [ 8 , 48 , 49 ]. In our previous study, by E 2 -treatment (100 μg/L/time, 2 h/time, 1 time/day, from 25 dah to 55 dah), feminization of XY T. rubripes was induced, and the results of the transcriptomic analysis of gonads showed that a large number of DEGs and pathways involved in the process of feminization of XY T. rubripes [ 22 ]. For example, the expression of cyp19a1a , foxl2 , gsdf , dmrt1 , cyp11a1 , cyp17a1 , hsd3b1 , hsd17b1 and cyp11c1 changed dramatically in the gonad when torafugu were treated with E 2 .…”

“…Our previous study also found that the body lengths of larvae in E 2 -treated groups were less than those in the control group and the survival rate of larvae was only 17%. It proved that E 2 significantly inhibits growth, survival and gonad development in torafugu larvae [ 22 ]. The results were similiar to data from both tilapia [ 73 ] and rainbow trout [ 74 ], in addition to results from another study on torafugu [ 48 ].…”

“…In T. rubripes , YY males can be used to produced monosex male for the study of gonadal sex differentiation and increasing interest in commercial production. Although whether the sex reversed XY or XX torafugu are fertile or not has not been confirmed until now, it has been demonstrated that treatment of XX T. rubripes with aromatase inhibitor (fadrozole or letrozole) results in the inhibition of ovarian cavity formation [ 8 , 20 , 22 ]. Treatment of genetically XY T. rubripes with E 2 , prior to morphological sex differentiation, can induce feminization.…”

“…Treatment of genetically XY T. rubripes with E 2 , prior to morphological sex differentiation, can induce feminization. Several genes involved in E 2 -induced feminization in the gonads of T. rubripes have been characterized in our previous study [ 22 ].…”