NERVE GROWTH CONE LOCOMOTION

描述（来自申请人摘要） 轴突在发育过程中和损伤后的延伸是一个先决条件 神经回路的形成。生长促进和抑制 影响对于引导轴突延伸通过 复杂的组织环境。这些影响通过以下方式发挥作用： 调节生长锥的运动性，顶端的结构 轴突的延伸。在查明 并表征抑制和促进分子，在一些 在某些情况下，用于转导其效应的第二信使已经被 研究了相比之下，在查明 运动的分子效应器是运动的最终目标， 细胞外影响该项目的总体目标是 描述一个重要的效应器，并确定它如何影响 生长锥导航和轴突延伸。当前的焦点 一项关于肌球蛋白IIB的提案，这是一种可能参与 生长锥运动和神经突张力产生的几个方面。 尽管其他机械酶存在于生长锥中， 肌球蛋白的丰度、定位和机械化学性质 IIB使其成为生长锥车削效应器的主要候选者， 牵引力的产生、突出和张力的调节 生产探讨肌球蛋白IIB在生长锥中的作用 运动和轴突延伸，神经元来源于小鼠，其中肌球蛋白 IIB已被基因靶向部分或完全消除 用于细胞培养实验。来自肌球蛋白IIB的生长锥 将分析敲除动物的突出缺陷， 回缩，皮质张力，逆行流，牵引力，神经突 张力和能力，以回应吸引或排斥 环境线索为了直接测试肌球蛋白IIB双极 长丝有助于这些过程，申请人将确定 如果这些过程中的任何缺陷可以通过表达 或者是绿色荧光蛋白B肌球蛋白II B（其可以形成双极 丝）或绿色荧光蛋白B重酶解肌球蛋白II B（其 不能形成双极丝）融合蛋白在细胞中从 令人倾倒的动物这些研究的结果将有助于我们 理解生长中的轴突如何响应环境的能力， 它就能找到目标

DESCRIPTION (from applicant's abstract) Axon extension during development and following injury is a prerequisite for the formation of neuronal circuitry. Growth promoting and inhibitory influences are important for directing axon extension through the complex tissue environment. These influences exert their effects by regulating the motility of the growth cone, the structure at the tips of extending axons. Considerable progress has been made in identifying and characterizing inhibitory and facilitatory molecules, and in some cases, second messengers for transducing their effects have been studied. In contrast, less progress has been made in identifying the molecular effectors of motility that are the ultimate targets of the extracellular influences. The overall aim of this project is to characterize an important effector and determine how it influences growth cone navigation and axon extension. The focus of the current proposal is on myosin IIB, a mechanoenzyme likely to participate in several aspects of growth cone motility and neurite tension production. Although other mechanoenzymes are present in growth cones, the abundance, localization, and mechanical-chemical properties of myosin IIB make it a leading candidate for an effector in growth cone turning, production of traction force, regulation of protrusion and tension production. To investigate the role of myosin IIB in growth cone motility and axon extension, neurons derived from mice in which myosin IIB has been partially or completely eliminated by gene targeting will be used in cell culture experiments. Growth cones from myosin IIB knockout animals will be analyzed for deficits in protrusion and retraction, cortical tension, retrograde flow, traction force, neurite tension and the ability to turn in response to attractive or repulsive environmental cues. To directly test the role that myosin IIB bipolar filaments contribute to these processes, the applicants will determine if any deficits in these processes can be eliminated by expressing either green fluorescent protein B myosin IIB (which can form bipolar filaments) or green fluorescent protein B heavy meromyosin IIB (which cannot form bipolar filaments) fusion proteins in the cells from the knockout animals. Results from these studies will contribute to our ability to understand how a growing axon responds to its environment as it navigates to its target.