Bao Zheng-Zheng
Department of Medicine and Cell Biology, Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Brain Res. 2008 Feb 4;1192:165-77. doi: 10.1016/j.brainres.2007.01.116. Epub 2007 Feb 2.
The initial step of retinal ganglion cell (RGC) axon pathfinding involves directed growth of RGC axons toward the center of the retina, the optic disc, a process termed "intraretinal guidance". Due to the accessibility of the system, and with various embryological, molecular and genetic approaches, significant progress has been made in recent years toward understanding the mechanisms involved in the precise guidance of the RGC axons. As axons are extending from RGCs located throughout the retina, a multitude of factors expressed along with the differentiation wave are important for the guidance of the RGC axons. To ensure that the RGC axons are oriented correctly, restricted to the optic fiber layer (OFL) of the retina, and exit the eye properly, different sets of positive and negative factors cooperate in the process. Fasciculation mediated by a number of cell adhesion molecules (CAMs) and modulation of axonal response to guidance factors provide additional mechanisms to ensure proper guidance of the RGC axons. The intraretinal axon guidance thus serves as an excellent model system for studying how different signals are regulated, modulated and integrated for guiding a large number of axons in three-dimensional space.
视网膜神经节细胞（RGC）轴突寻路的初始步骤涉及RGC轴突向视网膜中心即视盘的定向生长，这一过程被称为“视网膜内导向”。由于该系统具有易接近性，并且借助各种胚胎学、分子学和遗传学方法，近年来在理解RGC轴突精确导向所涉及的机制方面取得了重大进展。当轴突从遍布整个视网膜的RGC延伸时，随着分化波一起表达的多种因子对RGC轴突的导向很重要。为确保RGC轴突正确定向、局限于视网膜的视神经纤维层（OFL）并正确穿出眼球，不同组的正向和负向因子在这个过程中协同作用。由多种细胞黏附分子（CAM）介导的成束以及轴突对导向因子反应的调节提供了额外的机制，以确保RGC轴突的正确导向。因此，视网膜内轴突导向是研究如何调节、调制和整合不同信号以在三维空间中引导大量轴突的极佳模型系统。
