Soverchia L, Carotti M, Andreu-Vieyra C, Mosconi G, Cannella N, Habibi H, Polzonetti-Magni A M
Dipartimento di Scienze Farmacologiche e Medicina Sperimentale, Università degli Studi di Camerino, via Scalzino 3, Camerino (MC), Italia.
Mol Reprod Dev. 2007 Jan;74(1):57-67. doi: 10.1002/mrd.20484.
It has been proposed that gonadotropin-releasing hormone (GnRH) plays an autocrine/paracrine regulatory role in mammalian and fish ovaries. The marine teleost gilthead seabream is an interesting model since, during the life span of the fish, gonadal tissues develop first as testes, which then regress allowing the development of ovarian follicles. Recent studies carried out in ovaries of the gilthead seabream have demonstrated that various GnRH transcripts as well as GnRH splicing variants are expressed. The mRNA level of several GnRH forms in the female and male areas of the switching gonad, and their possible role in this process, were further investigated. The results here reported show that sGnRH, cGnRH-II, and sbGnRH transcripts are locally expressed during gilthead seabream gonadal differentiation; the expression of the three GnRH forms was found to differ among the morphologically defined areas of the switching gonad, as demonstrated by applying reverse transcription-polymerase chain reaction (RT-PCR), together with in situ hybridization, and semiquantitative PCR analyses. Moreover, the hypothesis that GnRH forms may regulate testicular regression via an apoptotic mechanism was investigated by analyzing the different areas of switching gonads for caspase-3 activity as a measure of apoptosis. Our results showed a marked increase of caspase-3 activity in the area corresponding to the regressing testes in which a significant decrease of testosterone production was also found. The present findings demonstrate that the changes in the endogenous GnRH transcripts could be related with the gonadal differentiation in gilthead seabream, and that exogenous GnRH plays a role by stimulating apoptosis in the degenerating testis.
有人提出,促性腺激素释放激素(GnRH)在哺乳动物和鱼类卵巢中发挥自分泌/旁分泌调节作用。海水硬骨鱼金头鲷是一个有趣的模型,因为在鱼的生命周期中,性腺组织首先发育为睾丸,然后退化,从而使卵巢卵泡得以发育。最近在金头鲷卵巢中进行的研究表明,各种GnRH转录本以及GnRH剪接变体都有表达。进一步研究了几种GnRH形式在性腺转换期雌雄性区域的mRNA水平及其在这一过程中的可能作用。这里报告的结果表明,sGnRH、cGnRH-II和sbGnRH转录本在金头鲷性腺分化过程中在局部表达;通过逆转录聚合酶链反应(RT-PCR)、原位杂交和半定量PCR分析表明,这三种GnRH形式的表达在性腺转换期形态学定义的区域之间存在差异。此外,通过分析性腺转换期不同区域的caspase-3活性作为细胞凋亡的指标,研究了GnRH形式可能通过凋亡机制调节睾丸退化的假说。我们的结果显示,在与退化睾丸相对应的区域,caspase-3活性显著增加,同时还发现睾酮产量显著下降。目前的研究结果表明,内源性GnRH转录本的变化可能与金头鲷的性腺分化有关,并且外源性GnRH通过刺激退化睾丸中的细胞凋亡发挥作用。