DEVELOPMENT OF NEURONAL SPECIFICITY

描述(研究人员摘要)：生长锥体，生长提示 轴突被认为是神经元的寻路器官。他们 通过直接的丝状径向接触感觉到许多指导信号，但它已经 不清楚接触实际上是如何引导生长锥体的。这项建议 重点关注接触中介指导的一个令人惊讶的具体方面 用时间推移显微镜在分离的细胞中检测到 文化。感觉神经元的生长锥体对 与他们通常在禽类中遇到的三个种群进行接触 胚胎。丝状径向接触特别改变了 增长锥体本身。1)局部接触后部硬化症 抑制面纱的延伸。2)局部接触雪旺细胞 刺激大面纱的突起，增加面纱的稳定性。3) 接触前硬化症会增加双侧丝状足突 覆盖整个生长锥，然后局部刺激 优惠合并。这些生理上相关的反应是 足以偏向行进方向，并调解诸如 作为回避，但比粗暴的行为更具有不变性。他们就这样 似乎是与寻路最相关的组成部分。这个 这些反应的特殊性强烈证明了在 分子水平。在接触时，特定的配体-受体结合很可能 以调节可区分的第二信使系统，这些信使系统导致特定的 细胞骨架动力学的改变。调查其中的每一个 元素反过来，这些不变的反应将被用作分析。目标 1表征了细胞表面的分子活性，这是两个 通过测试试点研究中涉及的候选人的反应。目标2 评估钙和其他第二信使候选者在 三种回答中的每一种。目标3描述细胞骨架变化 在与每个种群接触时，相互作用将被光学记录， 使用或不使用外源化学物质处理，并表征 详细地说。这项工作将阐明控制轴突的机制。 寻路，这是人类神经发育的基础过程。

DESCRIPTION (Investigator's Abstract): Growth cones, the growing tips of axons, are considered the pathfinding organ of the neuron. They sense many guidance cues by direct filopodial contact, but it has been unclear how the contact actually directs growth cones. This proposal focuses on a surprisingly specific aspect of contact-mediated guidance that was detected using time-lapse microscopy in dissociated cell culture. Growth cones of sensory neurons respond specifically to contact with three populations that they normally encounter in the avian embryo. Filopodial contact specifically alters the motile activity of the growth cone itself. 1) Contact with posterior sclerotome locally inhibits extension of veils. 2) Contact with Schwann cells locally stimulates protrusion of large veils and increases veil stability. 3) Contact with anterior sclerotome increases protrusion of both filopodia and veils throughout the growth cone and then locally stimulates preferential consolidation. These physiologically relevant responses are sufficient to bias the direction of travel and to mediate behaviors such as avoidance, but are more invariant than the gross behavior. They thus appear to be the component that is most relevant to pathfinding. The specificity of the responses strongly argues for specificity at the molecular level. On contact, specific ligand-receptor binding is likely to modulate distinguishable second messenger systems that cause specific alterations in cytoskeletal dynamics. To investigate each of these elements in turn, these invariant responses will be used as assays. Aim 1 characterizes cell surface molecular activities essential for two of the responses by testing candidates implicated in pilot studies. Aim 2 assesses the role of calcium and other second messenger candidates in each of the three responses. Aim 3 characterizes cytoskeletal changes on contact with each population Interactions will be optically recorded, with or without treatments with exogenous chemicals, and characterized in detail. This work will elucidate mechanisms that control axonal pathfinding, a process fundamental to human neural development.