Insights into the Evolution of Chordate Body Plans Through Correlated Developmental Genetic and Fate Mapping Studies of the Early Embryos of Amphioxus

amphioxus是一种较低的脊索动物，代表了与脊椎动物最接近的无脊椎动物亲戚。近年来，文昌鱼相对较晚发育阶段的基因表达数据有助于表明文昌鱼和脊椎动物之间的身体部位同源性。例如，神经基因的表达图谱表明文昌鱼（以及引申义，脊椎动物的近祖）的主要脑区与脊椎动物的脑区是同源的。相比之下，对文昌鱼早期发育过程中基因表达的了解相对较少。在脊椎动物中，这些早期作用基因在建立信号中心（组织者）、建立主要体轴和组织的大规模模式中起着关键作用。这一建议是集中在基因参与文昌鱼中枢神经系统的初始建立和早期区域化。最终目的是验证一种假设，即在文昌鱼和脊椎动物的最后一个共同祖先中，神经系统的建立和大规模模式的机制已经基本就位。这项研究包括两种紧密相连的方法。首先是分离和研究文昌鱼同源的已知在早期神经系统发育中很重要的脊椎动物基因的表达。第二是利用重要的染料示踪来阐明与文昌鱼神经系统早期形态发生相关的细胞和组织运动，包括原肠胚形成、胚胎前后轴的延伸和区域特征的建立。综上所述，在细胞和组织运动的详细图谱背景下，关键发育基因的表达将为脊椎动物早期进化过程中中枢神经系统的建立和区域化机制的进化提供见解。

0078599HollandAmphioxus is a lower chordate that represents the closest living invertebrate relative of the vertebrates. In recent years, gene expression data from relatively late developmental stages of amphioxus have helped to indicate body part homologies between amphioxus and vertebrates. For instance, mapping the expression of neural genes has suggested that amphioxus (and, by extension, the proximate ancestor of the vertebrates) has major brain regions homologous to those of vertebrates. In contrast, relatively little is yet known about gene expression during early development of amphioxus. In the vertebrates, such early acting genes play key roles in setting up signaling centers (organizers), establishing primary body axes, and large-scale patterning of the tissues. This proposal is focused on genes involved in the initial establishment and early regionalization of the amphioxus central nervous system. The ultimate aim is to test the hypothesis that mechanisms for establishing and large-scale patterning of the nervous system were already largely in place in the last common ancestor of amphioxus and the vertebrates. The research comprises two tightly linked approaches. The first is to isolate and study the expression of amphioxus homologs of vertebrate genes known to be important in early nervous system development. The second is to use vital dye tracing to elucidate cell and tissue movements associated with the early morphogenesis of the amphioxus nervous system, including gastrulation, extension of the anterior-posterior axis of the embryo, and establishment of regional identities. Taken together, the expression of key developmental genes in the context of a detailed map of cell and tissue movements will provide insights into the evolution of mechanisms involved in the establishment and regionalization of the central nervous system during the early evolution of the vertebrates.