SENSORY AXON PATHFINDING

感觉轴突寻路

• 批准号: 6092233
• 负责人: Marcia G Honig
• 金额: $ 2.5万
• 依托单位: UNIVERSITY OF TENNESSEE HEALTH SCI CTR
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-08-15 至 2000-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6092233
• 关键词: afferent nerve; antigen antibody reaction; cell adhesion molecules; cell cell interaction; chick embryo; confocal scanning microscopy; developmental neurobiology; immunologic assay /test; motor neurons; neuronal guidance; tissue /cell culture

The long-range goal of this research is to understand how growing sensory axons choose the correct pathways to follow in the developing chick hindlimb. Previous work has shown that, as they enter the limb, axons that will project along one peripheral nerve become segregated from axons that will project along other peripheral nerves. The proposed studies will examine how various cell adhesion molecules (CAMs), expressed on the surfaces of sensory and motoneuron axons, influence the interactions that occur between growing axons and thereby contribute to the ability of sensory axons to sort out correctly into nerve-specific bundles. To do this, antibodies that block the function of various CAMs (e.g. G4/L1, N- cadmerin, NCAM, SCI/DM-GRASP) or an enzyme, endoneuraminidase N, that removes the polysialic acid from NCAM and consequently enhances CAM- mediated adhesivity, will be injected directly into the hindlimb in ovo. The aims are: l) to determine the consequences for sensory axons of perturbing CAM function, starting at a time when motoneuron axons have already sorted out into nerve-specific bundles at the base of the limb but most sensory axons are still entering the plexus (i.e. at St.25). Retrograde labeling will be used to assess the effects of such perturbations on the segmental pattern of projections. Confocal laser scanning microscopy and various combinations of axonal tracing (retrograde and anterograde) together with immunofluorescence procedures to distinguish between sensory and motoneuron axons will be used to ascertain how axonal trajectories, the rate of axonal outgrowth, the extent of fasciculation between axons, and the spatial relationships among different types of axons are altered in the experimental embryos in comparison to normal and control embryos. 2) to determine the consequences of perturbing CAM function, starting at a time when motoneuron axons and the first sensory axons are entering the spinal nerves (i.e. at St.20-21). The intent of these studies is to alter the initial associations between motoneuron axons and some sensory axons and to thereby test whether the initial position a sensory axon occupies in the spinal nerves determines which peripheral nerve it later grows along. 3) to assess the roles of CAMs in mediating interactions between sensory and motoneuron axons, by using similar types of perturbations, in a simplified tissue culture system in which the two types of axons are forced to-row together. Together, these studies will increase our understanding of the mechanisms underlying sensory axon guidance in the chick hindlimb, of the ways in which interactions among axons can affect pathfinding decisions, and of the roles of CAMs in mediating interactions among axons. The latter is of particular importance since relatively little is known about the role of CAMs in the development of the central nervous system and yet it is clear, based on the consequences of exposure to certain toxic agents and the neurological manifestations of several genetic disorders, that proper CAM functioning is essential for the normal development of the nervous system.

这项研究的长期目标是了解感官的生长如何 轴突选择发育中的雏鸡遵循的正确路径 后肢。先前的研究表明，当轴突进入肢体时， 将沿着一根周围神经投射，与轴突分离 会沿着其他周围神经投射。拟议的研究将 检查各种细胞粘附分子 (CAM) 如何在 感觉和运动神经元轴突的表面，影响相互作用 发生在生长的轴突之间，从而有助于 感觉轴突正确地分类成神经特异性束。要做的事 这种抗体可以阻断各种 CAM 的功能（例如 G4/L1、N- cadmerin、NCAM、SCI/DM-GRASP）或一种酶，神经氨酸内切酶 N， 去除 NCAM 中的聚唾液酸，从而增强 CAM- 介导的粘附性，将直接注射到卵内的后肢。 目的是： l) 确定感觉轴突的后果 扰动 CAM 功能，从运动神经元轴突具有的时间开始 已经在肢体基部整理成神经特异性束，但是 大多数感觉轴突仍在进入神经丛（即在 St.25）。 逆行标签将用于评估此类影响 对投影分段模式的扰动。共焦激光 扫描显微镜和轴突追踪的各种组合（逆行 和顺行）与免疫荧光程序一起 区分感觉轴突和运动神经元轴突将用于确定 轴突轨迹、轴突生长速率、轴突生长程度 轴突之间的束束，以及不同轴突之间的空间关系 与实验胚胎相比，轴突类型发生了改变 正常胚胎和对照胚胎。 2）确定干扰的后果 CAM 功能，开始于运动神经元轴突和第一个 感觉轴突进入脊神经（即在 St.20-21）。这 这些研究的目的是改变之间的最初关联 运动神经元轴突和一些感觉轴突，从而测试是否 感觉轴突在脊神经中占据的初始位置决定 后来它沿着哪条周围神经生长。 3）评估角色 CAM 介导感觉轴突和运动神经元轴突之间的相互作用 在简化的组织培养中使用类似类型的扰动 在该系统中，两种类型的轴突被迫排列在一起。 总之，这些研究将增加我们对机制的理解 雏鸡后肢的基本感觉轴突引导，其方式 轴突之间的哪些相互作用可以影响寻路决策，以及 CAM 在介导轴突间相互作用中的作用。后者是属于 特别重要，因为人们对它的作用知之甚少 CAM 参与中枢神经系统的发育，但很明显， 基于接触某些有毒物质的后果以及 几种遗传性疾病的神经学表现，适当的 CAM 功能对于神经系统的正常发育至关重要。