GENETICS OF NOTOCHORD DEVELOPMENT

本研究的长期目标是了解作用模式 控制脊索发育的基因 脊索在轴向中胚层的形成中起着关键作用 结构和中枢神经系统在胚胎发育过程中。缺陷 脊索中的异常导致中轴骨骼的畸形或发育不全 和脊髓的损伤。而脊索的功能 建立，很少有人知道的遗传因素，控制其 发展和完整性，从而影响图案形成过程。 对脊索有不同特异性影响的突变的存在 形成表明i）在躯干中脊索的形成 和尾巴是由不同的基因控制的发育过程 这些基因在不同的时间特异性地起作用， 沿着前后轴沿着不同的区域。 为了理解在明显的时间上的分子机制， 脊索发育和完整性的空间差异， 分离和功能特性的基因参与的 对这些进程的管理至关重要。突变体分析 脊索的正常发育和完整性 在不同的时间和不同的区域受到特定的扰动，沿着 体轴是分离这些基因的关键。 在本提案中，我们将重点分析在细胞和 分子水平的3个这样的突变：丹佛斯的短尾（Sd）， 影响脊索早沿着其整个长度，截断（tc）， 作用较晚，仅作用于脊索尾部，Etl4lacZ， 一种新的lacZ-增强子-陷阱诱导的EtI4突变（增强子-陷阱- 基因座-4）基因，仅影响脊索的最后端 与Sd紧密相连但又不同。具体目标是 建议是： l）研究这些基因的作用的细胞自主性，并评估这些基因的作用。 在嵌合体中携带这些突变的细胞的发育潜力 胚胎 2)分析由Etl4lacZ插入突变的基因，并确定其 功能 3)用YAC克隆起始，通过染色体步移克隆Sd基因 在紧密连锁的Etl4基因上，确定Sd的遗传基础 突变并分析Sd基因及其功能 对这些基因及其作用方式的分析应该有助于 了解明显区域化的生物学意义 基因在脊索发育中的作用。

The long-term objective of this study is to understand the mode of action of genes controlling notochord development. The notochord plays a pivotal role in patterning axial mesodermal structures and the central nervous system during embryogenesis. Defects in the notochord lead to malformations or agenesis of the axial skeleton and of the spinal cord. Whereas the functions of the notochord are well established, little is known about the genetic elements that control its development and integrity and thus influence pattern forming processes. The existence of mutations with different specific effects on notochord formation suggests that i) the formation of the notochord in the trunk and tail are developmental processes governed by distinct genetic elements, and ii) these genes act specifically at different times and in different regions along the anterior-posterior axis. To understand the molecular mechanisms underlying the apparent temporal and spatial differences of notochord development and integrity, the isolation and functional characterization of genes involved in the regulation of these processes is essential. The analysis of mutants in which the normal development and the integrity of the notochord are specifically perturbed at different times and in different regions along the body axis is the key to isolate such genes. In this proposal we will focus on the analysis at the cellular and molecular level of 3 such mutations: Danforth's short tail (Sd), which affects the notochord early along its entire length, truncate (tc), which acts later and only on the caudal part of the notochord, and Etl4lacZ, a novel lacZ-enhancer-trap-induced mutation at the EtI4 (Enhancer-trap- Iocus-4) gene which affects only the very posterior end of the notochord and is closely linked to but distinct from Sd. The specific aims of this proposal are to: l) study the cell autonomy of the action of these genes and assess the developmental potential of cells carrying these mutations in chimeric embryos 2) analyze the gene mutated by the Etl4lacZ insertion and determine its function 3) clone the Sd gene by chromosomal walking with YAC clones starting at the closely linked Etl4 gene, determine the genetic basis for the Sd mutation and analyze the Sd gene and its function The analysis of these genes and their mode of action should help to understand the biological significance of the apparent regionalization of gene action in notochord development.