Qi Xin, Zhou Wenyi, Wang Qingqing, Guo Liang, Lu Danqi, Lin Haoran
State Key Laboratory of Biocontrol, Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China.
Endocrinology. 2017 Apr 1;158(4):860-873. doi: 10.1210/en.2016-1550.
Gonadotropin-inhibitory hormone (GnIH) plays a critical role in regulating gonadotropin-releasing hormone, gonadotropin hormone, and steroidogenesis in teleosts. In the present study, we sought to determine whether 17β-estradiol (E2) acts directly on GnIH neurons to regulate reproduction in goldfish, a seasonal breeder, and we investigated the role of estrogen receptors (ERs) in mediating this process. We found that GnIH neurons coexpress three types of ERs. Ovariectomy and letrozole implantation into female goldfish at the vitellogenic stage elicited a substantial decrease in the expression of GnIH messenger RNA (mRNA), and E2 supplementation abolished this effect. In primary cultured hypothalamus cells, E2 increased GnIH mRNA levels; surprisingly, selective ERα and ERβ agonists showed opposite effects in regulating GnIH mRNA levels. Using genome walking, we isolated a 2329-bp section of the GnIH promoter sequence, and 7 half-estrogen response elements (EREs) were found in the promoter region. Luciferase assays and electrophoretic mobility shift assay results show that the half-ERE element at -2203 is the key site for competitive binding between ERα and ERβ. Ovariectomy and letrozole implantation into female goldfish in the maturating stage did not change the GnIH mRNA expression levels. Taken together, these findings suggest that E2 binds to multiple types of ERs, which competitively bind to the same half-ERE binding site of the GnIH promoter to achieve both positive and negative feedback in response to estrogen to regulate goldfish reproduction at different stages of ovarian development.
促性腺激素抑制激素（GnIH）在调节硬骨鱼的促性腺激素释放激素、促性腺激素和类固醇生成中起关键作用。在本研究中，我们试图确定17β-雌二醇（E2）是否直接作用于金鱼（一种季节性繁殖者）的GnIH神经元以调节繁殖，并且我们研究了雌激素受体（ERs）在介导这一过程中的作用。我们发现GnIH神经元共表达三种类型的ERs。在卵黄生成期对雌性金鱼进行卵巢切除和来曲唑植入，导致GnIH信使核糖核酸（mRNA）表达大幅下降，而补充E2消除了这种影响。在原代培养的下丘脑细胞中，E2增加了GnIH mRNA水平；令人惊讶的是，选择性ERα和ERβ激动剂在调节GnIH mRNA水平上表现出相反的作用。通过基因组步移，我们分离出GnIH启动子序列的一个2329碱基对的片段，并且在启动子区域发现了7个半雌激素反应元件（ERE）。荧光素酶测定和电泳迁移率变动分析结果表明，-2203处的半ERE元件是ERα和ERβ竞争性结合的关键位点。在成熟期对雌性金鱼进行卵巢切除和来曲唑植入并没有改变GnIH mRNA表达水平。综上所述，这些发现表明E2与多种类型的ERs结合，这些ERs竞争性地结合到GnIH启动子的同一个半ERE结合位点，以实现雌激素的正负反馈，从而在卵巢发育的不同阶段调节金鱼的繁殖。
