Mechanisms of Retinal Axon Pathfinding

描述（由申请人提供）：为了使生长中的轴突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和排斥信号做出反应。最近的研究表明，生长锥可以调节它们对特定信号的反应，甚至从吸引转变为排斥;然而，尚不清楚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如何整合体内的正信号和负信号，并测试它们对信号的反应如何随着它们的寻路而变化。建议的实验研究的角色，两类的指导线索，狭缝和netrins，在视网膜轴突寻路。狭缝被认为通过Astray/Robo 2受体发出排斥信号，而netrin被认为通过DCC受体发出吸引信号。Slit/Robo 2和netrin/DCC都已知可以引导视网膜轴突，但它们在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用于干扰体内Slit/Robo 2和netrin/DCC信号传导，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。斑马鱼视网膜顶盖系统不仅允许以精细的分辨率在体内可视化视网膜轴突，而且还允许精确地靶向扰动它们的体内环境。这里开发的结果和技术将有助于全面了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。总之，该项目将阐明斑马鱼视网膜轴突的指导在何处，何时以及如何需要Slit/Robo 2和netrin/DCC信号。由此产生的遗传和发育机制的知识将是重要的理解人类疾病，如白化病，影响视神经轴突的指导。这些知识对于设计逆转视神经变性的疗法也至关重要。更一般地说，这个项目将测试轴突指导的广泛原则，这对理解神经系统的布线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.