Marcus R C, Mason C A
Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
J Neurosci. 1995 Oct;15(10):6389-402. doi: 10.1523/JNEUROSCI.15-10-06389.1995.
The retinofugal pathway is a useful model for axon guidance because fibers from each eye project to targets on both sides of the brain. Studies using static and real time analyses in mice at E15-17 demonstrated that uncrossed axons from ventrotemporal retina diverge from crossed axons in the optic chiasm, where specialized resident cells may direct divergence. Other studies, however, suggest that pioneering uncrossed retinal axons derive from a different retinal region, take a different course, and enter the ipsilateral optic tract independent of fiber-fiber interactions. We examine these differences by dye-labeling the earliest optic axons and immunocytochemically identifying cells in their path. The first optic axons arising from dorsocentral retina, enter the diencephalon at E12.5. All axons initially grow caudally, lateral to a radial glial palisade. In contrast to later growing axons, early uncrossed axons enter the ipsilateral optic tract directly. Crossed axons enter the glial palisade and course medially, then anteriorly, in a pathway corresponding to the border of an early neuronal population that expresses SSEA-1, CD44, and beta-tubulin. Axon patterning occurs independent of fiber-fiber interactions from both eyes, as the first uncrossed axons enter the optic tract before crossed ones from opposite eye. These analysis, in conjunction with our previous studies during the principal period of retinal axon growth in the diencephalon, suggest that the adult visual projection arises from age-dependent variations in the types and relative contribution of cues along the path through the emerging optic chiasm.
视网膜传出通路是轴突导向的一个有用模型，因为来自每只眼睛的纤维投射到脑两侧的靶区。利用E15 - 17期小鼠进行的静态和实时分析研究表明，来自颞腹侧视网膜的未交叉轴突在视交叉处与交叉轴突分离，在视交叉处特定的驻留细胞可能引导这种分离。然而，其他研究表明，先驱性的未交叉视网膜轴突来自不同的视网膜区域，走不同的路径，并且独立于纤维 - 纤维相互作用进入同侧视束。我们通过对最早的视神经轴突进行染料标记并免疫细胞化学鉴定其路径中的细胞来研究这些差异。最早从背中央视网膜发出的视神经轴突在E12.5进入间脑。所有轴突最初都向尾侧生长，位于放射状胶质细胞栅栏的外侧。与后来生长的轴突不同，早期的未交叉轴突直接进入同侧视束。交叉轴突进入胶质细胞栅栏并向内侧走行，然后向前走行，其路径与表达阶段特异性胚胎抗原 - 1、CD44和β - 微管蛋白的早期神经元群体的边界相对应。轴突模式的形成独立于来自双眼的纤维 - 纤维相互作用，因为第一批未交叉轴突在来自对侧眼的交叉轴突之前进入视束。这些分析，结合我们之前在间脑视网膜轴突生长主要阶段的研究，表明成年视觉投射源于沿着通过新兴视交叉的路径的线索类型和相对贡献的年龄依赖性变化。
