Wang Qingqing, Qi Xin, Tang Haipei, Guo Yin, Li Shuisheng, Li Gaofei, Yang Xiaoli, Zhang Haifa, Liu Xiaochun, Lin Haoran
State Key Laboratory of Biocontrol, Guangdong Province Key Laboratory for Improved Variety Reproduction of Aquatic Economic Animals, Institute of Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China.
Key Laboratory of Aquatic Animal Breeding and Culturing for South China Sea, Ministry of Agriculture, PR China.
Comp Biochem Physiol B Biochem Mol Biol. 2017 Apr;206:26-34. doi: 10.1016/j.cbpb.2017.01.001. Epub 2017 Jan 8.
Gonadal steroids are critical factors in reproduction and sex reverse process. StAR (steroidogenic acute regulatory protein), transferring the cholesterol from the outer mitochondrial membrane to the inner membrane, is the rate-limiting factor of steroidogenesis. 3βHSD (3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase), converting Δ5-steroids into Δ4-steroids, is an important oxidoreductase in steroidogenesis. In the present study, StAR and 3βHSD1 were cloned and characterized from protogynous orange-spotted grouper. StAR cDNA contains an 861bp open reading frame (ORF), encoding a predicted protein of 286 amino acids, and the ORF of 3βHSD1 was 1125bp, encoding a predicted protein of 374 amino acids. The transcript of StAR was mainly expressed in gonad, while 3βHSD1 mRNA was predominantly detected in brain and gonad. In the previous study, we found the expression of GnIH mRNA level in male, as well as in 17 alpha-methyltestosterone (MT)-induced male fish was significantly higher than in female fish, this indicating that GnIH/GnIHR signaling might be involved in the regulation of sex reversal and male maintenance. In order to figure out the function of GnIH in steroidogenesis, the expression of StAR and 3βHSD1 regulated by GnIH was examined. In vitro study showed that treatment of cultured ovary fragments with gGnIH peptides significantly stimulated the expression of StAR and 3βHSD1. In addition, the mRNA levels of StAR and 3βHSD1 were significantly increased after intraperitoneal injection (i.p.) with gGnIH peptides. Moreover, during MT-induced sex change from female to male, the levels of StAR mRNA significantly increased by 5.2, 24.8 and 353.5 folds, and that of 3βHSD1 mRNA by 3.5, 32.5 and 55.4 folds at the 2nd, 4th and 6th week after MT implantation, respectively. Collectively, our results indicate that GnIH may be involved in the regulation of sex reversal or male maintenance by stimulating the expression of StAR and 3βHSD1 in protogynous grouper.
性腺类固醇是生殖和性逆转过程中的关键因素。类固醇生成急性调节蛋白（StAR）负责将胆固醇从线粒体外膜转运至内膜，是类固醇生成的限速因子。3β-羟基类固醇脱氢酶/Δ5-Δ4异构酶（3βHSD）可将Δ5-类固醇转化为Δ4-类固醇，是类固醇生成过程中的一种重要氧化还原酶。在本研究中，从雌性先熟的点带石斑鱼中克隆并鉴定了StAR和3βHSD1。StAR cDNA包含一个861bp的开放阅读框（ORF），编码一个预测的286个氨基酸的蛋白质，3βHSD1的ORF为1125bp，编码一个预测的374个氨基酸的蛋白质。StAR的转录本主要在性腺中表达，而3βHSD1 mRNA主要在脑和性腺中检测到。在先前的研究中，我们发现雄性以及经17α-甲基睾酮（MT）诱导的雄性鱼中促性腺激素抑制激素（GnIH）mRNA水平显著高于雌性鱼，这表明GnIH/GnIHR信号通路可能参与性逆转和雄性维持的调节。为了弄清楚GnIH在类固醇生成中的作用，检测了GnIH对StAR和3βHSD1表达的调控。体外研究表明，用促性腺激素抑制激素相关肽（gGnIH）处理培养的卵巢片段可显著刺激StAR和3βHSD1的表达。此外，腹腔注射（i.p.）gGnIH肽后，StAR和3βHSD1的mRNA水平显著升高。此外，在MT诱导的从雌性到雄性的性转变过程中，植入MT后第2、4和6周，StAR mRNA水平分别显著增加了5.2、24.8和353.5倍，3βHSD1 mRNA水平分别增加了3.5、32.5和55.4倍。总体而言，我们的结果表明GnIH可能通过刺激雌性先熟石斑鱼中StAR和3βHSD1的表达参与性逆转或雄性维持的调节。
