Mohamed J Shaik, Benninghoff Abby D, Holt G Joan, Khan Izhar A
Marine Science Institute, University of Texas at Austin, 750 Channel View Drive, Port Aransas, Texas 78373, USA.
J Mol Endocrinol. 2007 Feb;38(1-2):235-44. doi: 10.1677/jme.1.02182.
The cDNAs of the G protein-coupled receptor 54 (GPR54) and three prepro-gonadotropin-releasing hormones, GnRH-I (seabream GnRH), GnRH-II (chicken GnRH-II), and GnRH-III (salmon GnRH) were isolated and cloned from the brain of the teleost fish cobia, Rachycentron canadum. The cobia GPR54 cDNA was 95 and 51-56% identical to those of tilapia and mammalian models respectively. The GnRH cDNA sequences of cobia showed strong identities to those of tilapia, Atlantic croaker, red drum, and the seabass and seabream species. The real-time quantitative RT-PCR methods allowed detection of all three GnRH mRNAs on the first day after hatching (DAH). The GnRH-I mRNA levels, which were the lowest among the three GnRHs, increased gradually with two distinct peaks in larvae at 3 and 4 DAH. On the other hand, GnRH-II and GnRH-III mRNAs were significantly higher in larvae at 2 and 6 DAH compared with those on the preceding days. In addition, significant peaks of all the three GnRH mRNAs were observed in the brains of 26-day-old fish. The finding of higher GnRH-I and GnRH-II mRNAs in males than females at 153 DAH may be related to early puberty observed during the first year in laboratory-reared male cobia. Moreover, this study demonstrates for the first time the expression of GPR54 mRNA during larval development in a vertebrate species. The concomitant expression patterns of GPR54 and GnRH mRNAs during different stages of larval and juvenile developments, and during early puberty in male cobia suggest a potential relationship between GPR54 and multiple GnRHs during these stages of development consistent with the role of GPR54 in controlling GnRH release in mammals. The increase in GPR54 and GnRH mRNAs observed during early puberty in cobia is consistent with a similar change reported in pubertal rats. This finding together with the localization of GPR54 mRNAs on GnRH neurons in fish and mammals suggests that the GPR54-GnRH interactions may be conserved in different vertebrate groups.
从硬骨鱼军曹鱼（Rachycentron canadum）的大脑中分离并克隆了G蛋白偶联受体54（GPR54）以及三种前体促性腺激素释放激素，即促性腺激素释放激素I（鲈鱼促性腺激素释放激素）、促性腺激素释放激素II（鸡促性腺激素释放激素II）和促性腺激素释放激素III（鲑鱼促性腺激素释放激素）的cDNA。军曹鱼GPR54 cDNA与罗非鱼和哺乳动物模型的GPR54 cDNA分别有95%以及51 - 56%的同源性。军曹鱼的促性腺激素释放激素cDNA序列与罗非鱼、大西洋笛鲷、红鼓鱼以及海鲈和海鲷物种的促性腺激素释放激素cDNA序列有很强的同源性。实时定量RT - PCR方法能够在孵化后第一天（DAH）检测到所有三种促性腺激素释放激素的mRNA。促性腺激素释放激素I的mRNA水平在三种促性腺激素释放激素中最低，在幼虫期3和4 DAH时逐渐升高并出现两个明显峰值。另一方面，与前几天相比，促性腺激素释放激素II和促性腺激素释放激素III的mRNA在2和6 DAH的幼虫中显著更高。此外，在26日龄鱼的大脑中观察到所有三种促性腺激素释放激素mRNA的显著峰值。在153 DAH时雄性中促性腺激素释放激素I和促性腺激素释放激素II的mRNA高于雌性这一发现，可能与实验室饲养的雄性军曹鱼在第一年观察到的早熟有关。此外，本研究首次证明了脊椎动物物种幼虫发育过程中GPR54 mRNA的表达。军曹鱼幼虫和幼鱼发育不同阶段以及雄性军曹鱼早熟期间GPR54和促性腺激素释放激素mRNA的伴随表达模式表明，在这些发育阶段GPR54与多种促性腺激素释放激素之间存在潜在关系，这与GPR54在哺乳动物中控制促性腺激素释放激素释放的作用一致。军曹鱼早熟期间观察到的GPR54和促性腺激素释放激素mRNA的增加与青春期大鼠报道的类似变化一致。这一发现连同GPR54 mRNA在鱼类和哺乳动物促性腺激素释放激素神经元上的定位表明，GPR54 - 促性腺激素释放激素相互作用可能在不同脊椎动物类群中保守。
