Mechanisms of Retinal Axon Pathfinding

描述(申请人提供)：为了让生长轴突在发育中的大脑中找到它们的目标，它们的生长锥体必须对环境中的吸引和排斥信号做出反应。最近的研究表明，生长锥体可以调节它们对特定信号的反应，甚至从吸引切换到排斥；然而，目前还不知道这种情况是否发生在体内。斑马鱼的视觉系统非常适合研究生长锥体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发现而变化。拟议的实验研究了两类引导线索--狭缝和网状线索--在视网膜轴突寻路中的作用。狭缝被认为通过stastray/Robo2受体发出排斥信号，而netrins被认为通过DCC受体发出有吸引力的信号。Sit/Robo2和netrin/DCC都是已知的引导视网膜轴突的分子，但它们在该通路不同部分的作用尚不清楚。正向遗传、反向遗传和转基因方法的组合将被用于干扰体内的Sit/Robo2和Netrin/DCC信号，以测试这些信号在视网膜通路中的哪些位置是重要的，并测试它们的作用是否在通路的过程中发生变化。斑马鱼视网膜顶盖系统不仅可以在体内以精致的分辨率显示视网膜轴突，还可以精确地对其体内环境进行有针对性的扰动。这里开发的结果和技术将有助于全面理解引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。总而言之，这个项目将阐明斑马鱼视网膜轴突的引导在哪里、何时以及如何需要Sit/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人类疾病，如白化病，影响视轴突引导将是重要的。这一知识对于设计逆转视神经退化的疗法也是至关重要的。更广泛地说，这个项目将测试轴突引导的广泛原则，这些原则对于理解神经系统的连接和遗传性神经疾病的基础非常重要。

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.