Mutational Analysis of Notochord Development

描述（由申请人提供）：胚胎从单个细胞发展为包含数千个多种类型细胞的复杂生物体。这些细胞组装成具有精确结构的组织和器官。这种结构的复杂性在包括人类在内的脊椎动物中表现得最为极端。这里提出的研究将使用脊椎动物最接近的无脊椎动物亲属之一，海鞘。海鞘是原始的海洋脊索动物，具有与脊椎动物相同的基本结构或身体平面，但胚胎的细胞要少得多，并且受更小的基因组控制。这里提出的实验将利用发育突变体来研究两个过程：脊索的形态发生和非神经外胚层的模式。脊索是脊索动物的特征之一，脊索是理解组织形态发生的重要实验范例，具体的实验将集中在层粘连蛋白基因产物在组织和指导脊索细胞形成连贯组织中的作用。在缺乏这种基因产物的情况下，脊索细胞在体内无休止地游荡。实验将探讨层粘连蛋白基因产物如何与先前表征的细胞信号传导途径相互作用，这些细胞信号传导途径在指导脊索细胞运动中是重要的。第二种类型的突变体，将被调查破坏的海鞘幼虫的躯干外胚层的图案。在这种突变体中，各种畸形是明显的，最有趣的是缺乏特定的外胚层增厚，似乎是类似于脊椎动物基板。在缺乏这些板状结构的情况下，其他组织，特别是咽内胚层的发育是异常的。具体目标是确定负责产生这种表型的基因，并了解其正常功能。

DESCRIPTION (provided by applicant): An embryo goes from a single cell to a complex organism containing thousands of cells of multiple types. These cells assemble into tissues and organs with a precise architecture. The complexity of this architecture is at its most extreme in the group of animals that includes humans, the vertebrates. Research proposed here will use one of the closest invertebrate relatives of the vertebrates, the ascidian. Ascidians are primitive marine chordates that have the same basic architecture, or body plan, as the vertebrates, but as embryos have much fewer cells, and are under the control of a much smaller genome. Experiments proposed here will exploit developmental mutants to investigate two processes: the morphogenesis of the notochord and the patterning of the non-neural ectoderm. The notochord is one of the defining characteristics of the chordates, and the notochord is an important experimental paradigm for understanding tissue morphogenesis, specific experiments will focus on the role of a laminin gene product in organizing and directing the cells of the notochord to form a coherent tissue. In the absence of this gene product the notochord cells wander endlessly through the body. Experiments will explore how the laminin gene product interacts with previously characterized cell-signaling pathways known to be important in directing notochord cell motility. A second type of mutant that will be investigated disrupts the patterning of the trunk ectoderm of the ascidian larva. In this mutant various malformations are evident, the most interesting being the lack-of specific ectodermal thickenings that appear to be similar to vertebrate placodes. In the absence of these placode-like structures, the development of other tissues, in particular the pharyngeal endoderm, is abnormal. Specific aims are targeted at identifying the gene responsible for generating this phenotype, and understanding its normal function.