Modulatory axonal guidance cues

描述（由申请人提供）：来自原始申请：长投射轴突通过受损的中枢神经系统再生不良。一个关键原因是它们必须重新生长的环境包含许多生化信号，这些生化信号触发了抑制轴突生长的信号通路。在正常胚胎发育过程中，这些抑制性线索中的一些在引导轴突到达适当的目标中起重要作用。我们之前的工作表明，激活特定的g蛋白偶联信号通路，例如趋化因子SDF1激活其受体CXCR4，使轴突对几种不同的驱避引导信号的反应减弱。我们已经用组织培养实验中的药理学试剂和斑马鱼胚胎发生中的反义试剂部分表征了这种抗驱避信号通路。该项目的目的是：表征该通路中的其他信号步骤，识别在培养和胚胎中阻断该通路步骤的显性阴性蛋白，并研究该抗排斥信号通路在正常发育过程中如何影响轴突引导。由于该途径中的一些信号成分也存在于大麻素和阿片类药物途径中，因此我们的研究可能会确定受产前滥用药物暴露影响的发育事件。这些研究将进一步加深我们对正常发育过程中生长的轴突如何将多个引导信号整合到单个决策中的理解，并可能提出促进成熟中枢神经系统再生的新方法。

DESCRIPTION (provided by applicant): From the original application: Long projection axons regenerate poorly through the damaged central nervous system. One key reason is the environment through which they must re-grow contains many biochemical signals that trigger signaling pathways which inhibit axon outgrowth. Some of these inhibitory cues are repellents that play an important role in guiding axons to their appropriate targets during normal embryonic development. Our previous work has shown that activation of a specific G-protein coupled signaling pathway, for example by the chemokine SDF1 activating its receptor CXCR4, makes axons less responsive to several different repellent guidance cues. We have partially characterized this anti-repellent signaling pathway with pharmacological reagents in tissue culture experiments and with anti-sense reagents in zebrafish embryogenesis. The aims of this project are to: characterize additional signaling steps in the pathway, identify dominant-negative proteins that block steps in the pathway both in culture and in the embryo, and examine how this anti-repellent signaling pathway affects axon guidance during normal development. As some of the signaling components in this pathway are also found in the cannabinoid and opioid pathways, our studies may identify developmental events that are influenced by prenatal exposure to drugs of abuse. These studies will further our understanding of how multiple guidance cues are integrated into single decisions by growing axons during normal development and will likely suggest novel approaches to promoting regeneration in the mature central nervous system. For the supplemental revision written in response to NOT-OD-09-058 "NIH Announces the Availability of Recovery Act Funds for Competitive Revision Application": Neurotransmitters have been hypothesized to provide axonal guidance information in the developing nervous system. We will test whether the metababotropic GABAB receptor, signaling through the anti-repellent pathway we have discovered and characterized, is required for normal axonal pathfinding in vivo. PUBLIC HEALTH RELEVANCE: Spinal cord injuries leave approximately 10,000 people partially or fully paralyzed in the United States each year. The prognosis for these kinds of injuries is extremely poor since re-growth of long axonal processes in the central nervous system is very poor. This project discovered and is now characterizing a signaling pathway that makes axons resistant to repellent guidance cues like those that prevent axonal regeneration. This pathway has some components in common with the cannabinoid and opioid signaling pathways and may also identify developmental events that are sensitive to prenatal exposure to these drugs of abuse.