Xu Yong-Jiang, Liu Xue-Zhou, Liao Mei-Jie, Wang Han-Ping, Wang Qing-Yin
College of Marine Life Sciences, Ocean University of China, Qingdao, Shandong, China.
J Exp Zool A Ecol Genet Physiol. 2012 Aug;317(7):434-46. doi: 10.1002/jez.1736. Epub 2012 Jun 4.
In this study, the gonadotropin-releasing hormone (GnRH) genes in spotted halibut were cloned and sequenced by isolating their cDNAs. The species expressed three molecular forms of GnRH in the brain: chicken-type GnRH-II (cGnRH-II), seabream-type GnRH (sbGnRH), and salmon-type GnRH (sGnRH). Phylogenetic analysis divided the molecular forms of GnRHs into three branches: cGnRH-II branch, sGnRH branch, and fish-specific GnRH branch. The spatial expression showed that they had the highest expression levels in the brain. cGnRH-II was exclusively detected in the brain, while sbGnRH had a global expression pattern in all examined organs. sGnRH was detected in the brain, pituitary, and ovary. The temporal changes of brain GnRH mRNA expression levels were examined during ovarian maturation and postspawning, and the serum steroid hormones and gonadosomatic index (GSI) were recorded. Amounts of sbGnRH mRNA substantially elevated (P < 0.05) during ovarian maturation, which concomitant with considerable elevation of GSI and serum steroids levels. On the contrary, neither sGnRH nor cGnRH-II mRNA levels showed significant changes during ovarian maturation in this study. These results suggested that these three GnRH genes are the important regulators for the differential expression of GnRH in spotted halibut, and would help us better understand the reproductive endocrine mechanism of spotted halibut.
在本研究中，通过分离圆斑星鲽促性腺激素释放激素（GnRH）的cDNA对其基因进行了克隆和测序。该物种在脑中表达三种分子形式的GnRH：鸡型GnRH-II（cGnRH-II）、鲷型GnRH（sbGnRH）和鲑型GnRH（sGnRH）。系统发育分析将GnRH的分子形式分为三个分支：cGnRH-II分支、sGnRH分支和鱼类特异性GnRH分支。空间表达显示它们在脑中表达水平最高。cGnRH-II仅在脑中检测到，而sbGnRH在所有检测器官中呈现整体表达模式。sGnRH在脑、垂体和卵巢中被检测到。在卵巢成熟和产后期间检测了脑GnRH mRNA表达水平的时间变化，并记录了血清类固醇激素和性腺指数（GSI）。在卵巢成熟期间，sbGnRH mRNA的量显著升高（P < 0.05），这与GSI和血清类固醇水平的显著升高同时发生。相反，在本研究中，卵巢成熟期间sGnRH和cGnRH-II mRNA水平均未显示出显著变化。这些结果表明，这三个GnRH基因是圆斑星鲽GnRH差异表达的重要调节因子，将有助于我们更好地理解圆斑星鲽的生殖内分泌机制。
