Department of Biology, Faculty of Marine and Environmental Sciences and INMAR, University of Cádiz, CEIMAR, Puerto Real (Cádiz), Spain.
Department of Biology, Faculty of Marine and Environmental Sciences and INMAR, University of Cádiz, CEIMAR, Puerto Real (Cádiz), Spain.
Gen Comp Endocrinol. 2019 Aug 1;279:184-195. doi: 10.1016/j.ygcen.2019.03.015. Epub 2019 Mar 25.
Gonadotropin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide belonging to the RFamide peptide family that was first discovered in quail by Tsutsui and co-workers in the year 2000. Since then, different GnIH orthologues have been identified in all vertebrate groups, from agnathans to mammals. These GnIH genes synthesize peptide precursors that encompass two to four C-terminal LPXRFamide peptides. Functional and behavioral studies carried out in birds and mammals have demonstrated a clear inhibitory role of GnIH on GnRH and gonadotropin synthesis and secretion as well as on aggressive and sexual behavior. However, the effects of Gnih orthologues in reproduction remain controversial in fish with both stimulatory and inhibitory actions being reported. In this paper, we will review the main findings obtained in our laboratory on the Gnih system of the European sea bass, Dicentrarchus labrax. The sea bass gnih gene encodes two putative Gnih peptides (sbGnih1 and sbGnih2), and is expressed in the olfactory bulbs/telencephalon, diencephalon, midbrain tegmentum, rostral rhombencephalon, retina and testis. The immunohistochemical study performed using specific antibodies developed in our laboratory revealed Gnih-immunoreactive (ir) perikarya in the same central areas and Gnih-ir fibers that profusely innervated the brain and pituitary of sea bass. Moreover, in vivo studies revealed the inhibitory role of centrally- and peripherally-administered Gnih in the reproductive axis of male sea bass, by acting at the brain (on gnrh and kisspeptin expression), pituitary (on gnrh receptors and gonadotropin synthesis and release) and gonadal (on androgen secretion and gametogenesis) levels. Our results have revealed the existence of a functional Gnih system in sea bass, and have provided evidence of the differential actions of the two Gnih peptides on the reproductive axis of this species, the main inhibitory role in the brain and pituitary being exerted by the sbGnih2 peptide. Recent studies developed in our laboratory also suggest that Gnih might be involved in the transduction of photoperiod and temperature information to the reproductive axis, as well as in the modulation of daily and seasonal rhythmic processes in sea bass.
促性腺激素抑制激素（GnIH）是一种下丘脑神经肽，属于 RFamide 肽家族，于 2000 年由 Tsutsui 及其同事在鹌鹑中首次发现。自那时以来，不同的 GnIH 同源物已在从无颌类到哺乳动物的所有脊椎动物中被鉴定出来。这些 GnIH 基因合成包含两个到四个 C 末端 LPXRFamide 肽的肽前体。在鸟类和哺乳动物中进行的功能和行为研究表明，GnIH 对 GnRH 和促性腺激素的合成和分泌以及攻击性行为和性行为具有明显的抑制作用。然而，鱼类中 GnIH 同源物在生殖中的作用仍存在争议，既有刺激作用也有抑制作用的报道。在本文中，我们将回顾我们实验室在欧洲鲈鱼（Dicentrarchus labrax）GnIH 系统中获得的主要发现。鲈鱼 gnih 基因编码两种假定的 GnIH 肽（sbGnih1 和 sbGnih2），并在嗅球/端脑、间脑、中脑被盖、头颈部脊髓、视网膜和睾丸中表达。使用我们实验室中开发的特异性抗体进行的免疫组织化学研究显示，GnIH-免疫反应（ir）神经元存在于相同的中枢区域，并且 GnIH-ir 纤维大量支配鲈鱼的大脑和垂体。此外，体内研究表明，中枢和外周给予的 GnIH 通过作用于大脑（对 gnrh 和 kisspeptin 表达）、垂体（对 gnrh 受体和促性腺激素合成和释放）和性腺（对雄激素分泌和配子发生）水平，在雄性鲈鱼的生殖轴中发挥抑制作用。我们的研究结果表明，在鲈鱼中存在功能性 GnIH 系统，并提供了证据表明两种 GnIH 肽对该物种生殖轴的不同作用，sbGnih2 肽在大脑和垂体中主要发挥抑制作用。我们实验室最近进行的研究还表明，GnIH 可能参与将光周期和温度信息传递到生殖轴，并调节鲈鱼的昼夜和季节性节律过程。
