Yoshiura Y, Suetake H, Aida K
Graduate School of Agriculture and Agricultural Life Sciences, The University of Tokyo, Bunkyo, 113-8657, USA.
Gen Comp Endocrinol. 1999 Apr;114(1):121-31. doi: 10.1006/gcen.1998.7242.
The duality of gonadotropin (GTH) is well-established in relatively modern teleosts. In primitive teleosts such as eel and catfish, however, only a single GTH (GTH-II) has been isolated and characterized. Therefore, the objective of this study was to clarify the duality of GTH, particularly the presence of GTH-I in primitive teleosts. We attempted to obtain a cDNA encoding the beta subunit of GTH-I from Japanese eel, Anguilla japonica, as a representative primitive teleost species. Rapid amplification of cDNA ends (RACE) polymerase chain reaction (PCR) was used to amplify GTH-Ibeta cDNA prepared from immature male Japanese eel pituitaries, and the obtained PCR products were subcloned and sequenced. A degenerate PCR primer was designed based on a highly conserved region between teleost GTH-Ibeta and mammalian FSHbeta. DNA sequence analysis of the cloned PCR products confirmed the presence of the predicted complete coding region as well as the 5' and 3' untranslated regions. The deduced amino acid sequence from these clones showed high homology to goldfish GTH-Ibeta (60%), whereas the identity between Japanese eel GTH-Ibeta and GTH-IIbeta was lower (42%). Phylogenetic analysis confirmed that Japanese eel GTH-Ibeta belonged to the teleost GTH-Ibeta group. These results provide a definitive proof of the presence of two types of GTHs (GTH-I and GTH-II) in Japanese eel, as has been shown in other teleosts. The duality of GTHs is applicable for teleosts in general. Northern blot analysis showed the transcripts of Japanese eel GTH-Ibeta and GTH-IIbeta to be 1200 and 750 bases, respectively. GTH-Ibeta gene was expressed in immature fish, while GTH-IIbeta gene was expressed in spermiating males and ovulated females, suggesting that two GTHs are differentially expressed at different sexual stages and may play separate roles in the reproductive process in Japanese eel.
促性腺激素（GTH）的双重性在相对现代的硬骨鱼中已得到充分证实。然而，在像鳗鱼和鲶鱼这样的原始硬骨鱼中，仅分离并鉴定出了一种单一的GTH（GTH-II）。因此，本研究的目的是阐明GTH的双重性，特别是原始硬骨鱼中GTH-I的存在情况。我们试图从日本鳗鲡（Anguilla japonica）中获得编码GTH-Iβ亚基的cDNA，日本鳗鲡是一种具有代表性的原始硬骨鱼物种。采用cDNA末端快速扩增（RACE）聚合酶链反应（PCR）来扩增从未成熟雄性日本鳗鲡垂体中制备的GTH-Iβ cDNA，所得PCR产物进行亚克隆并测序。基于硬骨鱼GTH-Iβ和哺乳动物FSHβ之间的高度保守区域设计了简并PCR引物。对克隆的PCR产物进行DNA序列分析，证实了预测的完整编码区以及5'和3'非翻译区的存在。从这些克隆推导的氨基酸序列与金鱼GTH-Iβ具有高度同源性（60%），而日本鳗鲡GTH-Iβ和GTH-IIβ之间的同一性较低（42%）。系统发育分析证实日本鳗鲡GTH-Iβ属于硬骨鱼GTH-Iβ组。这些结果明确证明了日本鳗鲡中存在两种类型的GTH（GTH-I和GTH-II），正如在其他硬骨鱼中所显示的那样。GTH的双重性普遍适用于硬骨鱼。Northern印迹分析表明，日本鳗鲡GTH-Iβ和GTH-IIβ的转录本分别为1200和750个碱基。GTH-Iβ基因在未成熟鱼中表达，而GTH-IIβ基因在排精雄鱼和排卵雌鱼中表达，这表明两种GTH在不同性阶段差异表达，可能在日本鳗鲡的生殖过程中发挥不同作用。
