GnIH在半滑舌鳎性腺发育中的功能及作用机制

促性腺激素抑制激素(gonadotropin-inhibitory hormone, GnIH)是目前脊椎动物中唯一一种具有抑制生殖功能的下丘脑神经肽，然而其在鱼类生殖调控尤其是在性腺发育中的作用及其信号转导机制尚未完全阐明。以舌鳎为研究对象，申请人首次在鲆鲽鱼类中鉴定出了GnIH系统，初步阐明了其在下丘脑和垂体水平调控生殖的作用方式及下游信号通路。本项目拟进一步研究GnIH在性腺发育中的作用及分子机制：1）通过原位杂交和免疫组化明确GnIH及其受体在性腺中的细胞定位；2）通过在体实验和离体实验初步阐明GnIH对类固醇激素生成及性腺发育的影响；3）通过细胞转染和药理学方法研究ERK和Ca2+通路是否介导了GnIH的生理功能；4）研究GnIH与GnRH、kisspeptin之间信号互作。本项目可进一步完善GnIH在鱼类生殖调控中的作用机制，为揭示GnIH在雌雄性腺发育中功能差异提供理论依据。

Gonadotropin-inhibitory hormone (GnIH) is the only identified hypothalamic neuropeptide that directly inhibits reproduction in any vertebrate. However, it is not yet fully elucidated in fish regarding the physiological role of GnIH in the regulation of reproduction, especially in gonadal development, and the signal transduction mechanisms mediating the actions of GnIH. Using half-smooth tongue sole (Cynoglossus semilaevis) as a model, our previous results encompassed the first study reporting the existence of the GnIH system in the order Pleuronectiformes. In addition, we have preliminarily clarified the mode of GnIH action on the control of reproduction at the hypothalamic-pituitary level and the intracellular signaling pathways in response to GnIH. The aims of the present study, therefore, are to further evaluate the role of GnIH in paracrine/autocrine control of gonadal development and its molecular mechanisms. First, the cellular localization of GnIH and its receptor in the gonads will be analyzed by in situ hybridization and immunohistochemistry. Second, GnIH functions and implications in steroidogenesis and gonadal development will be assessed by in vivo and in vitro methords. Third, whether and how ERK and Ca2+ routes mediate the actions of GnIH will be investigated using cell transfection combined with a pharmacological approach. Furthermore, the potential interactions on cell signaling among GnIH, GnRH and kisspeptin will be examined. In summary, this study will contribute to advance our understanding of the action mechanisms of GnIH on the regulation of reproduction in teleosts, and provide an initial insight into the functional divergence of GnIH in gonadal development between males and females.