Roch Graeme J, Wu Sheng, Sherwood Nancy M
Department of Biology, University of Victoria, Victoria, BC, Canada V8W 3N5.
Gen Comp Endocrinol. 2009 Mar;161(1):3-12. doi: 10.1016/j.ygcen.2008.10.017. Epub 2008 Nov 1.
Modern fish are the result of major changes in evolution including three possible duplications of the whole genome. Retained duplicate genes are often involved with metabolism, transcription, neurogenic processes and development. Here we examine the consequences of the most recent (350 mya) teleost-specific duplication in five fishes (zebrafish, fugu, medaka, stickleback and rainbow trout) in regard to duplicate copies of hormones and receptors in the secretin superfamily. This subset of genes was selected as the superfamily is limited to ten hormones and their receptors and includes some important members: glucagon, growth hormone-releasing hormone (GHRH), pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP). We used reports from the literature and an extensive database search of the fish genomes to evaluate the status of the superfamily and its duplicate genes. We found that all five fish species have an almost complete set of orthologs with the human superfamily of hormones, although they lack secretin and its receptor. Receptor orthologs are present in zebrafish, fugu, medaka, stickleback and to a lesser extent in salmonids. Zebrafish retain duplicate copies for seven hormones and five receptors. Duplicated genes in fugu, medaka, stickleback and salmonids are also present, based mainly on genome annotation or mRNA transcription. Separate chromosome locations and synteny support zebrafish duplicates as the result of large-scale duplications. Novel changes in fish include the modification of a duplicate glucagon receptor to a GLP-1 receptor and, unlike humans, the presence of bioactive and specific PHI and GHRH-like peptide receptors. We conclude that fish duplicates in the secretin superfamily are a rich, mostly unexplored area for endocrine research.
现代鱼类是进化过程中重大变化的结果，包括可能出现的三次全基因组复制。保留下来的复制基因通常与代谢、转录、神经发生过程和发育有关。在此，我们研究了五种鱼类（斑马鱼、河豚、青鳉、棘鱼和虹鳟）中最近一次（3.5亿年前）硬骨鱼特有的基因复制对促胰液素超家族中激素和受体的复制拷贝的影响。选择该基因子集是因为该超家族仅限于十种激素及其受体，并且包括一些重要成员：胰高血糖素、生长激素释放激素（GHRH）、垂体腺苷酸环化酶激活多肽（PACAP）和血管活性肠多肽（VIP）。我们利用文献报道以及对鱼类基因组的广泛数据库搜索来评估该超家族及其复制基因的状况。我们发现，尽管这五种鱼类缺乏促胰液素及其受体，但它们几乎拥有与人类激素超家族完全对应的直系同源基因。受体直系同源基因存在于斑马鱼、河豚、青鳉、棘鱼中，在鲑科鱼类中存在程度较低。斑马鱼保留了七种激素和五种受体的复制拷贝。河豚、青鳉、棘鱼和鲑科鱼类中也存在复制基因，这主要基于基因组注释或mRNA转录。不同的染色体位置和共线性支持斑马鱼的复制基因是大规模复制的结果。鱼类中的新变化包括将一个复制的胰高血糖素受体修饰为胰高血糖素样肽-1受体，并且与人类不同的是，鱼类存在具有生物活性的特异性肽组氨酸异亮氨酸肽（PHI）和类生长激素释放激素肽受体。我们得出结论，促胰液素超家族中的鱼类复制基因是内分泌研究中一个丰富但大多未被探索的领域。
