Characterization of Gonadotropin-Releasing Hormone (GnRH) Genes From Cartilaginous Fish: Evolutionary Perspectives.
Characterization of Gonadotropin-Releasing Hormone (GnRH) Genes From Cartilaginous Fish: Evolutionary Perspectives.
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DOI：
10.3389/fnins.2018.00607
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发表时间：
2018
影响因子：
4.3
通讯作者：
Tostivint H
中科院分区：
文献类型：
--
作者：
Gaillard AL;Tay BH;Pérez Sirkin DI;Lafont AG;De Flori C;Vissio PG;Mazan S;Dufour S;Venkatesh B;Tostivint H
神经肽促性腺激素释放激素(GnRH)在生殖功能调控中起着重要作用。脊椎动物具有多种GnRH形式，主要分为三类，即GnRH1、GnRH2和GnRH3。为了更深入地了解脊椎动物中的GnRH基因家族，我们试图确定该家族的哪些同源基因存在于软骨鱼中。为此，我们搜索了这一组中具有代表性的三个物种的基因组和/或转录本，它们是小斑猫鲨、细颈青蟹、鲸鲨、犀牛和象鲨。在每个物种中，我们报告了三个GnRH基因的鉴定。在猫鲨和鲸鲨中，系统发育和同源性分析表明，这三个基因对应于GnRH1、GnRH2和GnRH3。在这两个物种中，GnRH1编码了一种新形式的GnRH，其一级结构确定如下：QHWSFDLRPG。在象鲨中，这三个基因对应于GnRH1a和GnRH1b，这是GnRH1基因的两个副本，加上GnRH2。软骨促性腺激素释放激素相关肽(GAP)的三维结构预测表明，猫鲨GAP1、GAP2和象鲨GAP2具有螺旋-环-螺旋(HLH)结构。在许多骨鱼Gap1和GAP2中观察到的这种结构，可能传递GAP生物活性。在象鲨GAP1a和GAP1b中没有观察到这种HLH型结构。至于到目前为止所描述的所有其他GAP3，没有观察到猫鲨或鲸鲨GAP3的典型3D HLH结构。RT-PCR分析表明，GnRH1、GnRH2和GnRH3基因在猫鲨脑中存在差异表达。GnRH1mRNAs主要分布在间脑，而GnRH2mRNAs和GnRH3mRNAs分别在中脑和端脑中含量最高。综上所述，我们的结果表明，脊椎动物祖先的GnRH基因谱系在软骨类中完全保守，而GnRH3基因可能在全头类中丢失。他们还表明，以前在硬骨脊椎动物大脑中描述的三个GnRH神经元系统也存在于软骨鱼类中。
The neuropeptide gonadotropin-releasing hormone (GnRH) plays an important role in the control of reproductive functions. Vertebrates possess multiple GnRH forms that are classified into three main groups, namely GnRH1, GnRH2, and GnRH3. In order to gain more insights into the GnRH gene family in vertebrates, we sought to identify which paralogs of this family are present in cartilaginous fish. For this purpose, we searched the genomes and/or transcriptomes of three representative species of this group, the small-spotted catshark, Scyliorhinus canicula, the whale shark, Rhincodon typus and the elephant shark Callorhinchus milii. In each species, we report the identification of three GnRH genes. In catshark and whale shark, phylogenetic and synteny analysis showed that these three genes correspond to GnRH1, GnRH2, and GnRH3. In both species, GnRH1 was found to encode a novel form of GnRH whose primary structure was determined as follows: QHWSFDLRPG. In elephant shark, the three genes correspond to GnRH1a and GnRH1b, two copies of the GnRH1 gene, plus GnRH2. 3D structure prediction of the chondrichthyan GnRH-associated peptides (GAPs) revealed that catshark GAP1, GAP2, and elephant shark GAP2 peptides exhibit a helix-loop-helix (HLH) structure. This structure observed for many osteichthyan GAP1 and GAP2, may convey GAP biological activity. This HLH structure could not be observed for elephant shark GAP1a and GAP1b. As for all other GAP3 described so far, no typical 3D HLH structure was observed for catshark nor whale shark GAP3. RT-PCR analysis revealed that GnRH1, GnRH2, and GnRH3 genes are differentially expressed in the catshark brain. GnRH1 mRNA appeared predominant in the diencephalon while GnRH2 and GnRH3 mRNAs seemed to be most abundant in the mesencephalon and telencephalon, respectively. Taken together, our results show that the GnRH gene repertoire of the vertebrate ancestor was entirely conserved in the chondrichthyan lineage but that the GnRH3 gene was probably lost in holocephali. They also suggest that the three GnRH neuronal systems previously described in the brain of bony vertebrates are also present in cartilaginous fish.