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，我们研究了脊索动物起源和进化的分子和发育机制。我们首先通过分子系统发育分析确定棘皮动物、半索动物和脊索动物有共同的祖先，形成后口动物单系群。脊索动物是脊索动物最显着的特征，脊索动物的名字就来源于这个器官。在海鞘蝌蚪幼虫中，脊索由 40 个细胞组成，脊索细胞的特化是在 32 细胞阶段由相邻内胚层细胞发出的信号诱导的。诱导后，海鞘类 Brachyury 基因仅在脊索细胞中表达，并且该基因对脊索形成发挥主要控制作用。 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 20 个。这些基因编码与脊索形成和功能相关的多种不同蛋白质，但编码转录因子的基因很少。半索动物在后口动物中占据着关键的系统发育地位，因为它们表现出棘皮动物样幼虫形态和脊索动物样成虫形态。因此，对半索动物发育基因的表达和功能的分析可以深入了解后口动物身体结构的进化。我们表征了 Brachyury 基因、forkhead/HNF-3 基因（负责脊索动物胚胎中内胚层和脊索形成的基因）和 Pax 1/9 基因（负责脊索动物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索动物身体结构的进化。