UPMC Univ Paris 06, UMR 7144 CNRS - Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, F-29682, Roscoff, France.
BMC Evol Biol. 2010 Feb 25;10:62. doi: 10.1186/1471-2148-10-62.
Crustacean Hyperglycemic Hormone (CHH) family peptides are neurohormones known to regulate several important functions in decapod crustaceans such as ionic and energetic metabolism, molting and reproduction. The structural conservation of these peptides, together with the variety of functions they display, led us to investigate their evolutionary history. CHH family peptides exist in insects (Ion Transport Peptides) and may be present in all ecdysozoans as well. In order to extend the evolutionary study to the entire family, CHH family peptides were thus searched in taxa outside decapods, where they have been, to date, poorly investigated.
CHH family peptides were characterized by molecular cloning in a branchiopod crustacean, Daphnia magna, and in a collembolan, Folsomia candida. Genes encoding such peptides were also rebuilt in silico from genomic sequences of another branchiopod, a chelicerate and two nematodes. These sequences were included in updated datasets to build phylogenies of the CHH family in pancrustaceans. These phylogenies suggest that peptides found in Branchiopoda and Collembola are more closely related to insect ITPs than to crustacean CHHs. Datasets were also used to support a phylogenetic hypothesis about pancrustacean relationships, which, in addition to gene structures, allowed us to propose two evolutionary scenarios of this multigenic family in ecdysozoans.
Evolutionary scenarios suggest that CHH family genes of ecdysozoans originate from an ancestral two-exon gene, and genes of arthropods from a three-exon one. In malacostracans, the evolution of the CHH family has involved several duplication, insertion or deletion events, leading to neuropeptides with a wide variety of functions, as observed in decapods. This family could thus constitute a promising model to investigate the links between gene duplications and functional divergence.
甲壳动物高血糖激素（CHH）家族肽是神经激素，已知其调节十足目甲壳动物的几种重要功能，如离子和能量代谢、蜕皮和繁殖。这些肽的结构保守性，以及它们所显示的多种功能，使我们对其进化历史进行了研究。CHH 家族肽存在于昆虫（离子转运肽）中，也可能存在于所有节肢动物中。为了将进化研究扩展到整个家族，因此在十足目以外的分类群中搜索 CHH 家族肽，迄今为止，这些分类群中对其研究甚少。
通过对枝角类甲壳动物大型溞（Daphnia magna）和弹尾目昆虫球跳虫（Folsomia candida）的分子克隆，鉴定出 CHH 家族肽。还通过计算机从另一种枝角类、一种螯肢类和两种线虫的基因组序列中重建了编码这些肽的基因。这些序列被包含在更新的数据集，用于构建十足目动物 CHH 家族的系统发育。这些系统发育表明，在枝角类和弹尾目昆虫中发现的肽与昆虫 ITP 比与甲壳动物 CHH 更密切相关。数据集还用于支持有关节肢动物关系的系统发育假说，除了基因结构外，该假说还允许我们提出后生动物多基因家族在节肢动物中的两个进化情景。
进化情景表明，后生动物 CHH 家族基因起源于一个祖先的双外显子基因，而节肢动物的基因起源于一个三外显子基因。在软甲纲动物中，CHH 家族的进化涉及到几个重复、插入或缺失事件，导致具有广泛功能的神经肽，就像在十足目动物中观察到的那样。因此，该家族可以成为研究基因重复与功能分歧之间联系的有前途的模型。
