Characterization of gonadal soma-derived factor expression during sex change in the protogynous wrasse, Halichoeres trimaculatus

Background: Sex change in fishes provides a good experimental model for understanding the mechanisms and plasticity of sex determination and differentiation. The three-spot wrasse, Halichoeres trimaculatus is a protogynous hermaphrodite. During sex change from female to male, the ovary is replaced by the testis through the degeneration of oocytes and subsequent spermatogenesis. In the present study, we cloned a cDNA-encoding gonadal soma-derived factor (GSDF) from protogynous wrasse and examined its expression pattern in the sexually mature gonads and the sex-changing gonad induced experimentally by aromatase inhibition. Results: Expression of gsdf was predominantly observed in the testis, and it was mainly localized to the supporting cells surrounding the spermatogonia. In the ovary, only slight expression of gsdf was observed in morphologically undifferentiated supporting cells in contact with oogonia. During sex change, strong expression of gsdf appeared first in the supporting cells surrounding the gonial germ cells before the onset of spermatogenesis. Thereafter, the expression of gsdf continually increased in the supporting cells surrounding the proliferating spermatogonia throughout the sex change. Conclusions: These results suggest that gsdf is involved in the proliferation of spermatogonia and subsequent spermatogenesis in both the testis and the gonad in the early stages of sex change. Developmental Dynamics 242:388399, 2013. (c) 2013 Wiley Periodicals, Inc.

背景：鱼类的性别转变为理解性别决定和分化的机制及可塑性提供了一个良好的实验模型。三点濑鱼（Halichoeres trimaculatus）是一种先雌后雄的雌雄同体鱼类。在从雌性转变为雄性的过程中，卵巢通过卵母细胞的退化以及随后的精子发生过程被睾丸所取代。在本研究中，我们从先雌后雄的濑鱼中克隆了一种编码性腺体细胞衍生因子（GSDF）的cDNA，并检测了其在性成熟性腺以及通过芳香化酶抑制实验诱导的性别转变性腺中的表达模式。 结果：gsdf的表达主要在睾丸中观察到，并且主要定位于精原细胞周围的支持细胞。在卵巢中，仅在与卵原细胞接触的形态未分化的支持细胞中观察到轻微的gsdf表达。在性别转变过程中，在精子发生开始之前，gsdf首先在生殖细胞周围的支持细胞中强烈表达。此后，在整个性别转变过程中，gsdf在增殖的精原细胞周围的支持细胞中的表达持续增加。 结论：这些结果表明，gsdf参与了睾丸中精原细胞的增殖以及随后的精子发生，并且在性别转变的早期阶段也参与了性腺中的这些过程。《发育动力学》242:388 - 399, 2013。（c）2013威利期刊公司