INTEGRATING SIGNALS GUIDING AXONAL GROWTH AND BRANCHING

这个项目的长期目标是确定 引导大鼠脑内轴突生长、突触发生和突触修饰 发育中的脊椎动物大脑。在这里，我们建议在体内检查 大鼠视神经轴突的生长、分化和修饰 非洲爪蛙。个体视神经的生长和分枝 神经纤维在生长和分支形成时将被跟踪。 在它们的主要目标--视顶盖内的终端乔木，使用 微光视频显微镜、激光扫描共聚焦显微镜 和双光子激光扫描显微镜。观察的能力 体内发现的轴突提供了难得的机会 通过实验剖析引导脑内轴突生长的信号 与生物相关的背景。这些实验将利用我们的 神经营养因子BDNF是一种相关的神经营养因子 青蛙视觉系统发育的影响因素。这些实验将会 扩展之前的结果，这表明变化的 脑源性神经营养因子在靶组织中的水平迅速而显著地改变 视神经纤维的分支模式。尤其是， 实验将：-探索BDNF介导的后果 视网膜顶盖投射中的信号；-确定 神经元活动与脑电活动的相互作用(S) 神经营养因子；-使用融合蛋白遵循组装 突触特化。这些实验将扩展方法 通常只在文化中使用现代成像技术 以便研究活着的、完整的神经系统。因此， 它们提供了一个难得的机会来了解突触模式的动态 以及在形成图案时多个线索之间的整合 神经网络。

The long term goal of this project is to determine the cues that guide axonal growth, synaptogenesis and synaptic modification in the developing vertebrate brain. Here, we propose to examine in vivo the growth, differentiation and modification of optic nerve axons in the frog Xenopus laevis. The growth and branching of individual optic nerve fibers will be followed as they grow into and branch to form terminal arbors within their primary target, the optic tectum, using low light level video microscopy, laser scanning confocal microscopy and two-photon laser scanning microscopy. The ability to observe identified axons in vivo offers the rare opportunity to experimentally dissect the signals that guide axonal growth in a biologically relevant setting. The experiments will exploit our recent progress in showing that the neurotrophin BDNF is a relevant factor for visual system development in frog. The experiments will extend the previous results, which showed that the changing the levels of BDNF in the target tissue rapidly and dramatically altered the branching pattern of the optic nerve fibers. In particular, the experiments will: -explore the consequences of BDNF-mediated signaling in the retinotectal projection; - determine the interactions between neuronal activity and the action(s) of neurotrophins; - employ fusion proteins to follow the assembly of synaptic specializations. The experiments will extend approaches typically used only in culture by using modern imaging technologies to permit the living, intact nervous system to be studied. As such, they offer a rare glimpse into the dynamics of synaptic patterning and the integration between multiple cues in forming patterned neural networks.