Molecular Mechanisms of Sex Change in Fish

戈比鱼Trimma okinawa在其性腺中同时拥有卵巢和睾丸组织，并能够根据其社会环境在两个方向上重复变性。由于两个方向的性别变化都可以被社会操纵，冲绳虫提供了一个很好的动物模型来研究性别变化的分子机制。通过测定性腺中促性腺激素(FSH和LH)受体基因(GtHRs)表达的变化，探讨促性腺激素在性别变化中的作用。结果令人感兴趣，因为GtHR的表达被发现局限于相应性期的活跃性腺。当性别从雌性转变为雄性时，最初卵巢中FSHR和LHR的水平很高，一旦鱼意识到它在水族馆里比其他鱼大的事实，它们最终会在睾丸组织中上升。与此场景相反的是…如果将另一条比新变性的雄性更大的鱼引入这个水族馆，人们会观察到更多。性腺的交换开始于GtHR表达的转换，这种表达在视觉提示后12-24小时内可以辨认出来。我们的发现表明，连续变性鱼的性腺具有对社会线索做出不同反应的内在机制。此外，GtHR表达的这种位置转换也可以证实下丘脑-垂体-性腺轴的重要性。本研究采用体外器官培养系统，将雌二醇(estRadiation 1-17β，E_2)和11-酮-睾酮(11-ketotesterone，11kt)分别与雌二醇和11-酮-睾酮共同孵育，研究雌二醇和11-酮睾酮在性腺卵子发生和精子发生转化中的作用。在11kT的卵巢组织培养中，出现了精子、精子细胞和精母细胞的包囊，卵母细胞消失。相反，E_2处理不能使卵巢组织中的任何睾丸生殖细胞形成包囊。在11kT培养的睾丸组织中，可见精子、精子细胞和精母细胞的包囊，而在E2的培养下，睾丸组织完全变性。这一新开发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极好的体外系统。较少

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