Wu Limin, Wu Fengrui, Xie Lang, Wang Deshou, Zhou Linyan
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Science, Southwest University, Chongqing 400715, China.
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Science, Southwest University, Chongqing 400715, China; School of Biological and Food Engineering, Fuyang Teachers College, Key Laboratory of Embryo Development and Reproductive Regulation, Anhui Province, Fuyang 236000, China.
Mol Cell Endocrinol. 2016 May 15;427:33-44. doi: 10.1016/j.mce.2016.03.002. Epub 2016 Mar 4.
Two β-catenin (β-cat) genes exist in teleosts but little is known about their expression and function in ovarian development. We identified β-cat1 and β-cat2 from the Nile tilapia. β-cat1 and β-cat2 displayed a similar expression pattern in the ovary during development, and were mainly expressed in the oogonia and oocytes. In luciferase assays, β-cat1 activated the TOPFlash reporter dose-dependently, whereas β-cat2 failed to do so. Cotransfection of β-cat1 and β-cat2 synergistically enhanced the expression of the reporter. A specific interaction between β-cat1 and β-cat2 was also observed in a mammalian two-hybrid assay. Furthermore, tilapia recombinant Dkk1, an inhibitor of the β-cat pathway, decreased β-cat1 and β-cat2, while increased sox9, dmrt1, cyp11b2 and foxl2 expression in the in vitro cultured tilapia ovary, which could be abolished by simultaneous treatment with Bio, an agonist of β-cat. Consistently, β-cat1 or β-cat2 knockdown in XX fish by TALENs caused the retardation of ovarian differentiation and masculinization, as reflected by the upregulation of dmrt1, cyp11b2, sox9, and serum 11-KT level. On the contrary, serum E2 level was unchanged even though foxl2 transcription was upregulated. These data suggestes that both β-cat1 and β-cat2 are important members and play synergistic roles in the canonical Wnt signal pathway in fish. Independent of Foxl2-leading estrogen pathway, they might be involved in ovarian differentiation and repression of the male pathway gene expression in tilapia.
硬骨鱼中存在两个β-连环蛋白（β-cat）基因，但它们在卵巢发育中的表达和功能鲜为人知。我们从尼罗罗非鱼中鉴定出了β-cat1和β-cat2。β-cat1和β-cat2在卵巢发育过程中表现出相似的表达模式，主要在卵原细胞和卵母细胞中表达。在荧光素酶测定中，β-cat1能剂量依赖性地激活TOPFlash报告基因，而β-cat2则不能。β-cat1和β-cat2共转染能协同增强报告基因的表达。在哺乳动物双杂交试验中也观察到了β-cat1和β-cat2之间的特异性相互作用。此外，罗非鱼重组Dkk1（一种β-cat信号通路抑制剂）可降低β-cat1和β-cat2的表达，同时增加体外培养的罗非鱼卵巢中sox9、dmrt1、cyp11b2和foxl2的表达，而β-cat激动剂Bio同时处理可消除这种影响。同样，通过TALENs敲低XX鱼中的β-cat1或β-cat2会导致卵巢分化延迟和雄性化，表现为dmrt1、cyp11b2、sox9上调以及血清11-KT水平升高。相反，尽管foxl2转录上调，但血清E2水平未发生变化。这些数据表明，β-cat1和β-cat2都是重要成员，在鱼类的经典Wnt信号通路中发挥协同作用。它们可能独立于Foxl2主导的雌激素途径，参与罗非鱼的卵巢分化和雄性途径基因表达的抑制。
