Wu Guan-Chung, Tey Wei-Guan, Li Hau-Wen, Chang Ching-Fong
Department of Aquaculture, National Taiwan Ocean University, Keelung 20224, Taiwan.
Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung 20224, Taiwan.
PLoS One. 2015 Dec 29;10(12):e0145438. doi: 10.1371/journal.pone.0145438. eCollection 2015.
Androgen administration has been widely used for masculinization in fish. The mechanism of the sex change in sexual fate regulation is not clear. Oral administration or pellet implantation was applied. We orally applied an aromatase inhibitor (AI, to decrease estrogen levels) and 17α-methyltestosterone (MT, to increase androgen levels) to induce masculinization to clarify the mechanism of the sex change in the protogynous orange-spotted grouper. After 3 mo of AI/MT administration, male characteristics were observed in the female-to-male sex change fish. These male characteristics included increased plasma 11-ketotestosterone (11-KT), decreased estradiol (E2) levels, increased male-related gene (dmrt1, sox9, and cyp11b2) expression, and decreased female-related gene (figla, foxl2, and cyp19a1a) expression. However, the reduced male characteristics and male-to-female sex change occurred after AI/MT-termination in the AI- and MT-induced maleness. Furthermore, the MT-induced oocyte-depleted follicle cells (from MT-implantation) had increased proliferating activity, and the sexual fate in a portion of female gonadal soma cells was altered to male function during the female-to-male sex change. In contrast, the gonadal soma cells were not proliferative during the early process of the male-to-female sex change. Additionally, the male gonadal soma cells did not alter to female function during the male-to-female sex change in the AI/MT-terminated fish. After MT termination in the male-to-female sex-changed fish, the differentiated male germ cells showed increased proliferating activities together with dormancy and did not show characteristics of both sexes in the early germ cells. In conclusion, these findings indicate for the first time in a single species that the mechanism involved in the replacement of soma cells is different between the female-to-male and male-to-female sex change processes in grouper. These results also demonstrate that sexual fate determination (secondary sex determination) is regulated by endogenous sex steroid levels.
雄激素给药已被广泛用于诱导鱼类雄性化。性命运调控中性别转换的机制尚不清楚。采用了口服给药或埋植药粒的方法。我们口服施用了一种芳香化酶抑制剂（AI，以降低雌激素水平）和17α-甲基睾酮（MT，以提高雄激素水平）来诱导雄性化，以阐明雌性先熟的点带石斑鱼性别转换的机制。在施用AI/MT 3个月后，在雌性向雄性转变的鱼中观察到了雄性特征。这些雄性特征包括血浆11-酮睾酮（11-KT）升高、雌二醇（E2）水平降低、雄性相关基因（dmrt1、sox9和cyp11b2）表达增加以及雌性相关基因（figla、foxl2和cyp19a1a）表达降低。然而，在AI和MT诱导的雄性化中，AI/MT停药后出现了雄性特征减弱和雄性向雌性的性别转换。此外，MT诱导的卵母细胞耗尽的卵泡细胞（来自MT埋植）增殖活性增加，并且在雌性向雄性性别转换过程中，一部分雌性性腺体细胞的性命运转变为雄性功能。相比之下，在雄性向雌性性别转换的早期过程中，性腺体细胞没有增殖。此外，在AI/MT停药的鱼中，雄性向雌性性别转换过程中，雄性性腺体细胞没有转变为雌性功能。在雄性向雌性性别转换的鱼中MT停药后，分化的雄性生殖细胞显示出增殖活性增加以及休眠，并且在早期生殖细胞中没有表现出两性特征。总之，这些发现首次在单一物种中表明，石斑鱼雌性向雄性和雄性向雌性性别转换过程中，体细胞替代所涉及的机制是不同的。这些结果还表明，性命运决定（次级性别决定）受内源性性类固醇水平的调节。
