Nodal信号参与文昌鱼组织者形成的机制

脊索动物躯体构筑模式（body plan）的起源以及在个体发育中的形成机制是进化发育生物学研究的重要命题。胚胎的组织者（organizer）在脊椎动物躯体构筑模式形成过程中起中心作用，研究组织者的形成机制及其在胚胎发育中的作用是解析脊索动物躯体结构模式的核心内容。文昌鱼在进化上位于脊索动物门的基部，其基因组、胚胎及成体结构与脊椎动物相似，但却简单许多，是研究脊索动物组织者形成的极佳模型。我们前期实验结果暗示Nodal信号在文昌鱼组织者形成中具有重要作用。本申请项目将采用本实验室新近建立的基因敲除、转基因、单分裂球注射等的技术方法，对Nodal信号配体Nodal、Vg1、Vg1-like及其它信号成员开展研究，揭示Nodal信号在文昌鱼组织者形成中的作用，解析各配体在文昌鱼Nodal信号活化过程中相互配合机制。项目研究结果将为揭示脊索动物特有的躯体结构模式的发生、起源与演化机制提供重要线索。

Chordates, including vertebrates, tunicates and cephalochordates share a significantly different body plan from invertebrates by forming a neural tube, a notochord and somites on their dorsal sides. Clarifying how this body plan has originated and mechanisms directing its formation is one of the most important issues in the fields of developmental and evolutionary biology. Previous studies in vertebrates showed that the signaling center (called organizer), locating at the dorsal blastoporal lip of gastrulae, plays a key role during the formation of vertebrate body plan. Therefore, elucidating mechanisms underlying organizer formation and its contribution to embryonic development would be a key to studying how body plan is formed. Amphioxus represents the most ancient living chordates. Its embryogenesis, genome structure and morphology are vertebrate-like, but much simpler, making this animal an excellent model for addressing the above questions. Our preliminary studies show that the Nodal signaling is required for amphioxus organizer formation, and that amphioxus has evolved a new Nodal signaling ligand Vg1-like through duplication of the Vg1 gene. In the project, we will use state of the art techniques to study roles of Nodal signaling components, especially the ligands Nodal, Vg1 and Vg1-like, in the development of amphioxus organizer and their contributions to the establishment of amphioxus body plan. We will also pay efforts to clarify how Nodal, Vg1, and Vg1-like cooperate with each other to activate Nodal signaling in amphioxus embryos. Results generated by this study will provide essential insights for the development of body plan and its origin and evolution among chordates.