Molecular Mechanisms of Sex Change in Fish

虾虎鱼Trimma okinawae，在它的性腺中同时拥有卵巢和睾丸组织，并且能够根据它的社会环境在两个方向上反复改变性别。由于两性的性别变化可以被社会操纵，冲绳岛冲绳岛为研究性别变化的分子机制提供了一个很好的动物模型。通过测定性腺促性腺激素（FSH和LH）受体基因（GtHRs）在从女性到男性和从男性到女性的性别变化过程中的表达变化，探讨了促性腺激素在性别变化中的作用。结果是有趣的，因为GtHRs的表达被发现局限于相应性期的活跃性腺。当从雌性变为雄性时，最初卵巢的FSHR和LHR水平很高，一旦鱼意识到自己比水族馆里的其他鱼大，睾丸组织中的FSHR和LHR最终会上升。与此相反的是，更多的人观察到，如果另一条比刚变性的雄鱼更大的鱼被引入这个水族馆。性腺的交换开始于GtHR表达的转换，在视觉提示的12-24小时内可识别。我们的研究结果表明，连续变性鱼的性腺具有对社会线索作出不同反应的内在机制。此外，这种GtHR表达的位置转换也可以证实下丘脑-垂体-促性腺轴的重要性。濑鱼（Pseudolabrus sieboldi）从雌性变为雄性。为了研究雌二醇-17β (E2)和11-酮睾酮（11KT）在性腺内卵子与精子发生转化中的作用，我们在体外器官培养系统中分别用E2和11KT孵育卵巢和睾丸组织。11KT培养卵巢组织时，出现精子、精细胞和精母细胞的囊肿，而卵母细胞消失。相反，E2处理不能在卵巢组织中形成任何睾丸生殖细胞的囊肿。11KT在睾丸组织培养中，可见精子、精细胞和精母细胞的囊肿，E2在睾丸组织中完全变性。这一新发现的器官培养系统将为研究鱼类性别变化的分子机制提供一个良好的体外系统。少

The gobiid fish, Trimma okinawae, possesses ovarian and testicular tissues simultaneously in its gonad and is able to change sex repeatedly in both directions depending on its social surroundings. As sex change in both directions can be socially manipulated, T.okinawae provides an excellent animal model to investigate molecular mechanisms of sex change. The involvement of gonadotropins in sex change was examined by determining the changes in gonadotropin (FSH and LH) receptor gene (GtHRs) expression in gonads during the onset of sex changes from female to male and male to female. The results were intriguing as the expression of the GtHRs was found to be confined to the active gonad of the corresponding sexual phase. When the sex change was occurring from female to male, initially the ovary had high levels of FSHR and LHR, which eventually went up in the testicular tissue once the fish had realized the fact that it was bigger than the other in the aquarium. Opposite of this scenario was … More observed if another fish bigger than the newly sex-changed male was introduced into this aquarium. Swapping of the gonads started with switching of the GtHR expression that was discernible within 12-24 hrs of the visual cue. Our findings show that the gonads of successive sex changing fish possess the intrinsic mechanism to respond to the social cue differentially. Additionally, this location switching of GtHR expression also could substantiate the importance of hypothalamo-pituitary-gonadotropic axis.The wrasse, Pseudolabrus sieboldi, changes sex from female to male. In this study, to investigate the role of estradio1-17β (E2) and 11-ketotestosterone (11KT) in the conversion between oogenesis and spermatogenesis in the gonad, ovarian and testicular tissues were incubated with E2 or 11-KT respectively using in vitro organ culture system. In the culture of ovarian tissues with 11KT, the cysts of spermatozoa, spermatids, and spermatocytes appeared, while oocytes disappeared. On the contrary, E2 treatment could not organize the cysts of any testicular germ cells in ovarian tissues. In the culture of testicular tissues with 11KT, the cysts of spermatozoa, spermatids, and spermatocytes were observed, while with E2, there was a complete degeneration of testicular tissues. This newly developed organ culture system will provide an excellent in vitro system to study the molecular mechanisms of sex change in fish. Less