CAS Key Laboratory of Tropical Marine Bio-resources and Ecology (LMB), Guangdong Provincial Key Laboratory of Applied Marine Biology (LAMB), South China Sea Institute of Oceanology, Institute of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou, China.
CAS Key Laboratory of Tropical Marine Bio-resources and Ecology (LMB), Guangdong Provincial Key Laboratory of Applied Marine Biology (LAMB), South China Sea Institute of Oceanology, Institute of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou, China; University of Chinese Academy of Sciences, Beijing, China.
Gen Comp Endocrinol. 2019 Aug 1;279:196-202. doi: 10.1016/j.ygcen.2019.04.018. Epub 2019 Apr 16.
The gonadotropin-inhibitory hormone (GnIH) plays a negative role in the hypothalamic-pituitary-gonadal (HPG) axis by inhibiting gonadotropin secretion in vertebrates. Male pregnancy and ovoviviparous behavior are unique phenomena among vertebrates. To better understand the neuroendocrine regulatory mechanisms in ovoviviparous fish with male pregnancy, we identified the orthologous GnIH gene in the lined seahorse (Hippocampus erectus). The full-length cDNA of the GnIH precursor was 658 base pairs with an open reading frame of 528 base pairs that encoded a 175-amino acid prepro-GnIH peptide. The seahorse GnIH precursor contained two putative LPXRFamide peptides. Both seahorse LPXRFa-1 and LPXRFa-2 were found to be unique among vertebrates. The synteny blocks of GnIH gene loci were conserved in mammals and teleosts. Tissue distribution analysis revealed that seahorse GnIH mRNA was mainly expressed in the hypothalamus, with relatively high levels observed in the brood pouch. The expression patterns of seahorse GnIH during different reproductive stages and pregnancy stages were also detected, and GnIH mRNA expression was significantly reduced during the early puberty stage. In addition, GnIH mRNA expression was significantly increased during the pregnancy stage compared to non-pregnancy stages. In summary, our results reveal the existence of GnIH in ovoviviparous fish and suggest its involvement in regulation of reproductive behavior and male pregnancy in the male seahorse.
促性腺激素抑制激素（GnIH）通过抑制脊椎动物的促性腺激素分泌，在下丘脑-垂体-性腺（HPG）轴中发挥负调控作用。雄性妊娠和卵胎生行为是脊椎动物中独特的现象。为了更好地了解具有雄性妊娠的卵胎生鱼类的神经内分泌调节机制，我们在 lined seahorse（Hippocampus erectus）中鉴定了 GnIH 基因的直系同源物。GnIH 前体的全长 cDNA 为 658 个碱基对，开放阅读框为 528 个碱基对，编码 175 个氨基酸的 prepro-GnIH 肽。海马 GnIH 前体包含两个推定的 LPXRFamide 肽。两种海马 LPXRFa-1 和 LPXRFa-2 在脊椎动物中均为独特存在。GnIH 基因座的基因同线性块在哺乳动物和硬骨鱼中是保守的。组织分布分析显示，海马 GnIH mRNA 主要在下丘脑表达，在育雏囊中表达水平较高。还检测了海马 GnIH 在不同生殖阶段和妊娠阶段的表达模式，GnIH mRNA 表达在青春期早期明显降低。此外，与非妊娠阶段相比，妊娠阶段 GnIH mRNA 表达显著增加。总之，我们的结果揭示了 GnIH 在卵胎生鱼类中的存在，并表明其参与了雄性海马生殖行为和雄性妊娠的调节。
