Department of Aquaculture, National Taiwan Ocean University, Keelung, 20224, Taiwan.
Fish Physiol Biochem. 2013 Feb;39(1):95-101. doi: 10.1007/s10695-012-9667-4. Epub 2012 Jun 13.
Despite neurosteroidogenic enzymes are playing important roles in the regulation of brain development and function, the potential link between brain and gonad by the action of steroid hormones during gonadal sex differentiation is still not clear in teleosts. In this mini-review, we summarized our understanding on the early brain development related to the synthesis of neurosteroids and receptor signaling during gonadal sex differentiation in protogynous orange-spotted grouper, Epinephelus coioides (functional females for the first 6 years of life and start to sex change around the age of 7 years) and protandrous black porgy (functional males for the first 2 years of life but begin to change sex during the third year). We found a similar profile in the increased expression of brain aromatase gene (aromatatse B or cyp19a1b), aromatase activity, estradiol (E(2)), and estrogen signaling in the brain of both grouper and black porgy fish during gonadal sex differentiation. In contrast to mammals, teleost fish Cyp19a1b expressed in a unique cell type, a radial glial cell, which is acted as progenitors in the brain of developing and adult fish. In agreement with these pioneer studies, we demonstrated that the grouper cyp19a1b/Cyp19a1b was expressed in radial glial cells. Further, in vivo data in the grouper brain showed that exogenous E(2) upregulated Cyp19a1b immunoreactivity (ir) in radial glial cells. These data suggest the possible roles of Cyp19a1b and E(2) in early brain development which is presumably related to gonadal sex differentiation.
尽管神经甾体生成酶在调节大脑发育和功能方面发挥着重要作用，但在鱼类中，类固醇激素在性腺性别分化过程中对大脑和性腺之间的潜在联系仍不清楚。在这篇综述中，我们总结了我们对性反转石斑鱼（Epinephelus coioides，前 6 年为雌性，7 岁左右开始性反转）和雄性先熟黑鲷（Protandrous black porgy，前 2 年为雄性，但在第 3 年开始性反转）的早期脑发育与神经甾体合成和受体信号转导相关的认识。我们发现，在性反转石斑鱼和黑鲷的脑内，芳香化酶基因（芳香化酶 B 或 cyp19a1b）、芳香化酶活性、雌二醇（E(2)）和雌激素信号的表达增加，具有相似的特征。与哺乳动物不同的是，鱼类 Cyp19a1b 表达在一种独特的细胞类型中，即放射状胶质细胞，它在发育中和成年鱼类的脑内充当祖细胞。与这些开创性的研究一致，我们证明了石斑鱼的 cyp19a1b/Cyp19a1b 表达在放射状胶质细胞中。此外，在石斑鱼脑中的体内数据表明，外源性 E(2)上调了放射状胶质细胞中 Cyp19a1b 的免疫反应性（ir）。这些数据表明 Cyp19a1b 和 E(2)可能在早期脑发育中发挥作用，这可能与性腺性别分化有关。
