Cytoskeletal Signaling and Axon Guidance

描述(申请人提供)：在发育中的神经系统中，神经元必须将轴突延伸到它们正确的目标，以形成轴突支架，在其上进行功能性神经元连接。远侧轴突顶端的移行性生长锥体对引导信息进行感知和反应。这些研究的目的是利用线虫了解细胞骨架信号网络，该网络通过肌动蛋白细胞骨架将轴突引导信号与生长锥形态和突起的变化联系起来。在这项提案中，将使用遗传、分子和体内延时生长锥成像方法来剖析细胞骨架信号通路在生长锥形态和生长发育中的作用。许多影响轴突寻路的途径和分子已被发现。这些实验超越了“逐个基因”的方法来研究轴突寻路，而是被设计成了解分子如何在控制轴突寻路和生长锥形态的通路和网络中相互联系。第一个目的是测试CDC-42在轴突寻路中作用于Rac GTP酶上游的想法。第二个目的是研究CDC-42下游的TIAM-1/静物RAC GTP交换因子对RAC GTP酶的调控。AIM 2还旨在测试CDC42GEF UIG-1/CLG和Exc-5/Fgd1在调节CDC-42轴突路径中的作用。第三个目的是探讨MIG-15Nik激酶和Rack-1/活化C激酶受体的作用，以及它们与CDC-42下游的UNC-115/abLIM在Rac非依赖途径中的相互作用。第四个目标是综合前三个途径，研究这些途径在发育过程中对生长锥、丝状足的形成和形态的影响。这些实验的结果将大大有助于理解细胞骨架信号网络参与生长锥形态的目标，并将开始解决这些不同的通路在轴突发育中的细胞作用。

DESCRIPTION (provided by applicant): In the developing nervous system, neurons must extend axons to their correct targets to form an axon scaffold upon which functional neuronal connections are made. The migrating growth cone at the distal axon tip senses and responds to guidance information. The aim of these studies is to use C. elegans to understand the cytoskeletal signaling networks that link axon guidance signals to changes in growth cone morphology and outgrowth via the actin cytoskeleton. In this proposal, genetic, molecular, and in vivo time-lapse growth cone imaging approaches will be used to dissect the roles of cytoskeletal signaling pathways in growth cone morphology and outgrowth. Many pathways and molecules have been identified that affect axon pathfinding. These experiments move beyond the "gene by gene" approach to studying axon pathfinding and instead are designed to understand how molecules relate to one another in pathways and networks to control axon pathfinding and growth cone morphology. The first aim tests the idea that CDC-42 acts upstream of Rac GTPases in axon pathfinding. The second aim focuses on the control of Rac GTPases by the TIAM-1/Still life Rac GTP exchange factor (GEF) downstream of CDC-42. Aim 2 also is designed to test the role of the Cdc42 GEFs UIG-1/Clg and EXC-5/Fgd1 on regulation of CDC-42 in axon pathfinding. The third aim is to probe the role of the MIG-15 NIK kinase and RACK-1/Receptor for activated C kinase and their interaction with UNC- 115/abLIM downstream of CDC-42 in a Rac-independent pathway. The fourth aim integrates the first three and is to characterize the effects of these pathways on growth cone filopodia formation and morphology during outgrowth. The results of these experiments will significantly contribute to the goal of understanding the cytoskeletal signaling networks involved in growth cone morphology and will begin to address the cellular roles of these distinct pathways in axon development.