Developmental Mechanisms Involved in Animal Diversity : Molecular and Developmental Biological Studies on the Origin and Evolution of Chordates

动物多样性涉及的发育机制：脊索动物起源和进化的分子和发育生物学研究

基本信息

批准号：
07102012
负责人：
SATOH Noriyuki
金额：
$ 99.2万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Specially Promoted Research
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1999
项目状态：
已结题

项目摘要

In the present research, we have investigated molecular and developmental mechanisms underlying the origin and evolution of chordates. We first determined by molecular phylogenetic analyses that echinoderms, hemichordates and chordates share a common ancestor and form the monophyletic group of deuterostomes.Notochord is the most prominent feature of chordates, as the name of chordates originated from this organ. In ascidian tadpole larvae, notochord is composed of exactly 40 cells, and specification of the notochord cells is induced during the 32-cell stage by signals emanating from adjacent endoderm cells. Immediately after the induction, an ascidian Brachyury gene is expressed solely in the notochord cells, and the gene exerts a master control over the notochord formation. The Brachyury expression seems to activate about 40 downstream genes that are associated with the notochord formation. We characterized twenty of them by determining the complete nucleotide sequences of the cDNAs. These genes encode a broad spectrum of divergent proteins associated with notochord formation and function, but very few genes encoding transcription factors.Hemichordates occupy a critical phylogenetic position among deuterostomes since they exhibit echinoderm-like larval morphology and chordate-like adult morphology. Analyses of the expression and function of hemichordate developmental genes therefore provide insight into the evolution of deuterostome body plan. We characterized the expression of Brachyury gene, forkhead/HNF-3 gene (the gene responsible for endoderm and notochord formation in chordate embryos) and Pax 1/9 gene (the gene responsible for pharyngeal endoderm formation in chordate embryos). The expression patterns of these genes are suggestive for the evolution of chordate body plan.

在本研究中，我们研究了弦的起源和演变基础的分子和发育机制。我们首先通过分子系统发育分析来确定，棘皮动物，半色和和弦共有一个共同的祖先，并形成了粘粘膜的单系组。Notochord是弦的最突出的特征，作为弦弦的名称，起源于该器官。在海腹t幼虫中，脊索由正好的40个细胞组成，脊索细胞的规范是在32细胞阶段诱导的，这是通过从相邻的内胚层细胞中散发出的信号。诱导后立即，仅在脊索细胞中表达了海藻胸膜基因，并且该基因对脊索形成产生主要控制。 Brachyury表达似乎激活了大约40个与脊索形成相关的下游基因。我们通过确定CDNA的完整核苷酸序列来表征其中的二十个。这些基因编码与脊索形成和功能相关的广泛蛋白质，但很少编码转录因子的基因。示键率在氘代表体之间占据了关键的系统发育位置，因为它们表现出棘皮动物类似的幼虫形态和类似Chordate的成人形态。因此，分析半色外发育基因的表达和功能为氘代表身体计划的演变提供了深入的了解。我们表征了Brachyury基因，Forkhead/HNF-3基因（负责脊柱胚胎中内胚层和脊索形成的基因）和PAX 1/9基因（负责脊柱胚胎中咽内胚层形成的基因）的表达。这些基因的表达模式暗示了脊全体计划的进化。