Mechanisms of Retinal Axon Pathfinding

描述（由申请人提供）：为了在发育中的大脑中找到它们的目标，它们的生长锥必须对环境中的吸引力和排斥性信号做出反应。最近有研究表明，生长锥可以调节它们对特定信号的反应，甚至可以从吸引转变为排斥；然而，尚不清楚这是否发生在体内。斑马鱼的视觉系统非常适合研究生长锥如何在体内整合积极和消极的信号，并测试它们对信号的反应如何随着路径的变化而变化。本实验研究了裂孔和网络两类引导信号在视网膜轴突寻路中的作用。狭缝被认为是通过歧途/Robo2受体发出排斥信号，而网络被认为是通过DCC受体发出吸引信号。众所周知，Slit/Robo2和netrin/DCC都能引导视网膜轴突，但它们在不同通路中的作用尚不清楚。将使用正向遗传、反向遗传和转基因方法的组合来干扰体内的Slit/Robo2和netrin/DCC信号，以测试这些信号在视网膜通路中的重要位置，并测试它们的作用是否在通路过程中发生变化。斑马鱼视网膜顶板系统不仅可以在体内以精确的分辨率可视化视网膜轴突，而且可以对其体内环境进行精确的靶向扰动。这里开发的结果和技术将有助于全面了解指导视网膜轴突生长的所有信号，以及这些不同信号如何相互作用。总之，本项目将阐明斑马鱼视网膜轴突的引导在何时何地需要Slit/Robo2和netrin/DCC信号。由此产生的遗传和发育机制的知识对于理解影响视轴突指导的人类疾病（如白化病）将是重要的。这一知识对于设计治疗视神经变性的方法也是至关重要的。更广泛地说，这个项目将测试轴突引导的广泛原理，这对于理解神经系统的连接和遗传性神经疾病的基础很重要。

DESCRIPTION (provided by applicant): For growing axons to find their targets in the developing brain, their growth cones must respond to both attractive and repulsive signals in the environment. It has recently been shown that growth cones can modulate their responses to particular signal, even switching from attraction to repulsion; however, it is not known if this occurs in vivo. The zebrafish visual system is uniquely suited for studying how growth cones integrate positive and negative signals in vivo, and testing how their responses to signals change as they pathfind. The proposed experiments study the roles of two classes of guidance cues, Slits and netrins, in retinal axon pathfinding. Slits are thought to signal repulsively through the Astray/Robo2 receptor, while netrins are thought to signal attractively through the DCC receptor. Slit/Robo2 and netrin/DCC are both known to guide retinal axons, but their roles in different parts of the pathway are unknown. A combination of forward-genetic, reverse-genetic, and transgenic approaches will be used to perturb Slit/Robo2 and netrin/DCC signaling in vivo, to test where in the retinal pathway these signals are important, and to test whether their roles change over the course of the pathway. The zebrafish retinotectal system not only allows visualization of retinal axons in vivo with exquisite resolution, but also allows precisely targeted perturbations of their in vivo environment. The results and techniques developed here will help lead to a comprehensive understanding of all the signals that guide retinal axon growth, and how these different signals interact. In summary, this project will illuminate where, when, and how the guidance of zebrafish retinal axons requires Slit/Robo2 and netrin/DCC signaling. The resulting knowledge of genetic and developmental mechanisms will be important for understanding human diseases, such as albinism, that affect optic axon guidance. This knowledge will also be critical for designing therapies to reverse optic nerve degeneration. More generally, this project will test broad principles of axon guidance which are important for understanding the wiring of the nervous system and the basis of inherited neurological disease.