Burke R D, Angerer L M, Elphick M R, Humphrey G W, Yaguchi S, Kiyama T, Liang S, Mu X, Agca C, Klein W H, Brandhorst B P, Rowe M, Wilson K, Churcher A M, Taylor J S, Chen N, Murray G, Wang D, Mellott D, Olinski R, Hallböök F, Thorndyke M C
Department of Biology, University of Victoria, Victoria, POB 3020, STN CSC, Victoria, BC, Canada V8W 3N5.
Dev Biol. 2006 Dec 1;300(1):434-60. doi: 10.1016/j.ydbio.2006.08.007. Epub 2006 Aug 10.
The sequencing of the Strongylocentrotus purpuratus genome provides a unique opportunity to investigate the function and evolution of neural genes. The neurobiology of sea urchins is of particular interest because they have a close phylogenetic relationship with chordates, yet a distinctive pentaradiate body plan and unusual neural organization. Orthologues of transcription factors that regulate neurogenesis in other animals have been identified and several are expressed in neurogenic domains before gastrulation indicating that they may operate near the top of a conserved neural gene regulatory network. A family of genes encoding voltage-gated ion channels is present but, surprisingly, genes encoding gap junction proteins (connexins and pannexins) appear to be absent. Genes required for synapse formation and function have been identified and genes for synthesis and transport of neurotransmitters are present. There is a large family of G-protein-coupled receptors, including 874 rhodopsin-type receptors, 28 metabotropic glutamate-like receptors and a remarkably expanded group of 161 secretin receptor-like proteins. Absence of cannabinoid, lysophospholipid and melanocortin receptors indicates that this group may be unique to chordates. There are at least 37 putative G-protein-coupled peptide receptors and precursors for several neuropeptides and peptide hormones have been identified, including SALMFamides, NGFFFamide, a vasotocin-like peptide, glycoprotein hormones and insulin/insulin-like growth factors. Identification of a neurotrophin-like gene and Trk receptor in sea urchin indicates that this neural signaling system is not unique to chordates. Several hundred chemoreceptor genes have been predicted using several approaches, a number similar to that for other animals. Intriguingly, genes encoding homologues of rhodopsin, Pax6 and several other key mammalian retinal transcription factors are expressed in tube feet, suggesting tube feet function as photosensory organs. Analysis of the sea urchin genome presents a unique perspective on the evolutionary history of deuterostome nervous systems and reveals new approaches to investigate the development and neurobiology of sea urchins.
紫海胆基因组测序为研究神经基因的功能和进化提供了独特的机会。海胆的神经生物学特别引人关注，因为它们与脊索动物有着密切的系统发育关系，但具有独特的五辐射对称身体结构和不同寻常的神经组织。已鉴定出在其他动物中调节神经发生的转录因子的直系同源物，其中有几种在原肠胚形成前就在神经发生区域表达，这表明它们可能在保守的神经基因调控网络的顶端发挥作用。存在一个编码电压门控离子通道的基因家族，但令人惊讶的是，似乎不存在编码间隙连接蛋白（连接蛋白和泛连接蛋白）的基因。已鉴定出突触形成和功能所需的基因，并且存在神经递质合成和运输的基因。有一个庞大的G蛋白偶联受体家族，包括874种视紫红质型受体、28种代谢型谷氨酸样受体以及显著扩增的161种促胰液素受体样蛋白组。大麻素、溶血磷脂和黑皮质素受体的缺失表明这一组受体可能是脊索动物所特有的。至少有37种假定的G蛋白偶联肽受体，并且已鉴定出几种神经肽和肽激素的前体，包括SALMFamides、NGFFFamide、一种血管紧张素样肽、糖蛋白激素以及胰岛素/胰岛素样生长因子。在海胆中鉴定出一种神经营养因子样基因和Trk受体，这表明这种神经信号系统并非脊索动物所特有。已使用多种方法预测了数百个化学感受器基因，其数量与其他动物的数量相似。有趣的是，编码视紫红质、Pax6和其他几种关键哺乳动物视网膜转录因子同源物的基因在管足中表达，这表明管足起着光感受器的作用。对海胆基因组的分析为后口动物神经系统的进化历史提供了独特的视角，并揭示了研究海胆发育和神经生物学的新方法。
