养殖鲆鲽类早熟的能量信号分子及其内分泌调控功能

The emerging sexual precocity phenomenon in farmed flatfish becomes bottle neck of sustainable development of farming industry, however the underlying endocrine mechanism is unclear. Similar with mammals, the gonadal maturation of teleosts depends on balance between energy acquisition and expenditure. In the present project, we will investigate the endocrine regulation mechanism for farmed tongue sole, Cynoglossus semilaevis Günther from an energy point of view based on our progress in sex differentiation and gonadal development. We will focus on key energy signal-leptin, carry out studies on relationship between leptin and puberty onset by combining quantitative PCR test, in situ hybridization, gonadal hemigonadectomy, gene chip analysis, in vitro assay and verification, etc. We aim to: (1) reveal the polymorphism, spatial and temporal expression patterns of leptin and its receptors during gametogenesis in tongue sole; (2) identify the key signal molecules for puberty onset and determine their dosage-sensitive correlation with leptin regulation; (3) clarify the endocrine regulation function and possible pathways of leptin in body fat content and puberty onset finally. The predicted results could provide new clue and basic knowledge for study of endocrine mechanism for sexual precocity in tongue sole, enrich the biological function content of leptin. Furthermore, results from this project also could provide theoretical and technical support for construction of practical sexual precocity control technology for tongue sole and other farmed flatfishes.

养殖鲆鲽类性早熟问题日益凸显，但对其内分泌调控机制认识不足。与哺乳动物类似，硬骨鱼类性腺成熟过程依赖于能量获取和消耗分配平衡机制。本项目以能量代谢关键信号分子-瘦素（leptin）为着手点，聚焦我国鲆鲽类主养品种-半滑舌鳎性早熟的内分泌调控机制的科学问题，在前期对其配子发生及性腺分化发育研究的基础上，利用定量PCR、原位杂交、性腺切除、基因芯片、离体孵育等主要技术方法，揭示半滑舌鳎leptin及受体基因型的多态特性与时空表达模式，查明半滑舌鳎配子发生启动关键信号分子与leptin调控的剂量敏感关系，建立leptin对脂肪能量状态的指示关系及对初情期启动的内分泌调控图式，预期结果可为半滑舌鳎早熟的内分泌调控机制研究提供新的线索和基础资料，丰富leptin生物学功能内容，为构建半滑舌鳎及其他养殖鲆鲽鱼类性早熟调控技术理论与技术支撑。

鲆鲽类为我国北方海水养殖主要种类，近年来养殖鲆鲽类性早熟问题日益凸显，成为制约养殖产业提质增效的制约因素，但目前对其内分泌调控机制认识不足。与哺乳动物类似，硬骨鱼类性腺成熟过程依赖于能量获取和消耗分配平衡机制。本项目以能量代谢关键信号分子-leptin为着手点，聚焦我国鲆鲽类主养品种-半滑舌鳎性早熟的内分泌调控机制的科学问题，围绕阐释leptin及其受体对性腺发育和成熟过程的调控作用及机制，利用多种技术方法和手段开展了一系列相关研究。获得并解析了半滑舌鳎两种leptin基因和一种受体基因的结构及系统进化特性；认识了leptin及其受体的组织表达特征以及在早期生长发育阶段的时空表达模式，表明其在胚胎发育囊胚期、仔稚幼鱼转饵期和变态期可能具有重要的调控作用；分析了性腺分化过程中leptin及其受体表达模式、体脂肪含量变动的关系，发现了leptin系统与脂肪变动协同参与了半滑舌鳎性腺分化过程；验证了leptin及其受体在BPG轴上中下游全面参与了卵巢发育成熟周期的调控过程；获得了两种leptin基因的体外表达的重组蛋白，揭示了孵育条件下重组leptin蛋白以及性类固醇激素对内源性leptin及受体和其它生殖生长相关功能基因的调控作用。这些结果揭示了leptin及其受体在半滑舌鳎性腺分化、卵巢发育和周年成熟过程中可能起着重要的生理调控作用，也提示在性腺发育早期通过对内源性leptin系统的调控可有效控制性腺发育进程，从而为建立早熟调控技术提供了理论依据。项目的研究结果为养殖鲆鲽类性早熟的内分泌调控机制研究积累了基础资料，丰富了鱼类leptin生物学功能研究内容。