Guo Yin, Wang Qingqing, Li Gaofei, He Meng, Tang Haipei, Zhang Haifa, Yang Xiaoli, Liu Xiaochun, Lin Haoran
State Key Laboratory of Biocontrol, Institute of Aquatic Economic Animals and the Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China.
Marine Fisheries Development Center of Guangdong Province, Huizhou, China.
Mol Reprod Dev. 2017 Jun;84(6):495-507. doi: 10.1002/mrd.22800. Epub 2017 Apr 17.
Kisspeptins are considered critical regulators in the hypothalamic-pituitary-gonadal axis because they can stimulate secretion of Gonadotropin-releasing hormone in mammals, and may also mediate the feedback regulation of sex steroids in the hypothalamus. Two kiss1 paralogues (kiss1 and kiss2) were identified in teleosts, hinting at their increased complexity of signaling for sex-steroid feedback regulation. In the present study, molecular pathways by which 17β-estradiol (E ) exerted feedback regulation on two kiss genes, via three types of estrogen receptors, were investigated in the protogynous orange-spotted grouper (Epinephelus coioides). kiss2 expression in the brain significantly increased in ovariectomized orange-spotted groupers, while E replacement in ovariectomized fish reversed these changes to levels in the sham-surgery group; conversely, kiss1 expression did not change. Dual-label in situ hybridization showed that kiss1 and kiss2 neurons express erα, erβ1, and erβ2, indicating that E may directly regulate kiss1 and kiss2. Indeed, E treatment of transiently transfected HEK293T cells decreased the activity of both kiss promoters in the presence of erβ1 and erβ2 rather than erα. Further deletion and site-directed mutagenesis of the kiss promoters indicated that kiss1 is regulated by E via an estrogen-responsive element (ERE)-dependent, classical pathway utilized by Erβ1, as well as via an Activator protein 1 (Ap1)-dependent, non-classical pathway utilized by Erβ2. kiss2 was also differently regulated by E through the Creb transcription factor, utilized by Erβ1 as well as a half-ERE-dependent, classical pathway utilized by Erβ2. Taken together, multiple signaling pathways in orange-spotted grouper are clearly involved in the feedback regulation of E on kiss genes via different estrogen receptors.
亲吻素被认为是下丘脑 - 垂体 - 性腺轴中的关键调节因子，因为它们可以刺激哺乳动物促性腺激素释放激素的分泌，还可能介导下丘脑中性类固醇的反馈调节。在硬骨鱼中鉴定出了两个亲吻素1旁系同源物（kiss1和kiss2），这暗示了它们在性类固醇反馈调节信号传导方面的复杂性增加。在本研究中，在雌性先熟的点带石斑鱼（Epinephelus coioides）中研究了17β - 雌二醇（E）通过三种类型的雌激素受体对两个亲吻素基因进行反馈调节的分子途径。在切除卵巢的点带石斑鱼中，大脑中的kiss2表达显著增加，而切除卵巢的鱼中E替代将这些变化逆转至假手术组的水平；相反，kiss1表达没有变化。双标原位杂交显示kiss1和kiss2神经元表达erα、erβ1和erβ2，表明E可能直接调节kiss1和kiss2。事实上，在存在erβ1和erβ2而非erα的情况下，用E处理瞬时转染的HEK293T细胞会降低两个亲吻素启动子的活性。亲吻素启动子的进一步缺失和定点诱变表明，kiss1通过雌激素反应元件（ERE）依赖性经典途径由Erβ1调节，以及通过激活蛋白1（Ap1）依赖性非经典途径由Erβ2调节。kiss2也通过Creb转录因子由E进行不同调节，Creb转录因子由Erβ1利用，以及通过半ERE依赖性经典途径由Erβ2利用。综上所述，点带石斑鱼中的多种信号通路显然参与了E通过不同雌激素受体对亲吻素基因的反馈调节。
