目的 研究小鼠胚胎阶段Nogo-A在视网膜节细胞(RGCs)及其轴突上的表达及时程变化. 方法 取不同发育阶段的小鼠胚胎,采用免疫荧光染色,以激光扫描共焦显微镜观察Nogo-A在视觉传导通路中的表达.并采用免疫双标染色确定视网膜中表达Nogo-A蛋白的细胞类型. 结果 在视网膜发育的早期阶段(E12),Nogo-A密集表达于具有放射状形态的细胞上,Nogo-A免疫阳性产物出现在胞质、胞膜以及轴突上.Nogo-A与Tuj-1双标染色显示,此阶段的视网膜中几乎所有RGCs及其轴突都表达有Nogo-A;在稍晚的发育阶段(E13),视网膜中表达Nogo-A的RGCs数量明显减少,且仅出现在节细胞层以外的室周带和睫状体边缘区.在视网膜的神经纤维层,大部分RGCs轴突不再表达Nogo-A,仅有少量视觉纤维为Nogo-A免疫阳性;RGCs的神经发生基本完成后(E15), 视网膜中几乎检测不到Nogo-A免疫阳性的细胞,但视网膜纤维层仍有少量表达Nogo-A的节细胞轴突.与之类似,视神经盘、视茎、视交叉和视束都观察到少量Nogo-A免疫阳性的轴突.值得注意的是,视束中表达Nogo-A的纤维集中位于表浅部位,而此处恰为新近到达轴突的通过部位. 结论 Nogo-A在视网膜RGCs以及轴突上表达的时程变化和位置特点提示,新生RGCs及其轴突表达Nogo-A,成熟后RGCs内Nogo-A的表达则下调.推测新生RGCs及其轴突中表达的Nogo-A可能与减少轴突分叉等细胞的内在功能有关.“,”Objective To investigate the expression of Nogo-A in the retinal ganglion cells (RGCs) and their axons of mouse embryos and its time course changes. Methods Sections of retinofugal pathway of C57 mouse embryos at different developmental stages were immunostained with Nogo-A specific antibody and observed by a confocal microscopy. The identity of Nogo-A positive cells was partially revealed by double-staining together with Tuj-1. Results At the early stage of E12, Nogo-A was densely expressed in some radially-orientated cells in retina. The immunopositive signals appeared in the cytoplasm, on the cell membrane and axons. The double-labeling together with Tuj-1, a neuronal marker, showed that nearly all the RGCs and their axons expressed Nogo-A protein. At the later stage of E13, the number of Nogo-A positive neurons in retina decreased dramatically. And those Nogo-A positive RGCs were specifically located in the ventricular part and the ciliary margin zone of the retina. At this stage, only a very few axons maintained their Nogo-A expression in the fiber layer of the retina, while most lost their Nogo-A distribution. When most RGCs had fully differentiated at E15, there was no detectable Nogo-A immunopositive staining in the retina and only a few retinal fibers were Nogo-A immunopositive. The similar expression patterns of Nogo-A was found in a few axons along the optic disc, optic stalk, optic chiasm and optic tract. Worthy of note, the retinal axons with Nogo-A distribution in the optic tract were exclusively found in the superficial area, where the newly-arrived axons were traveling through during development. Conclusion The expression pattern and its time course change suggested that Nogo-A was an important protein expressed by the newly differentiated RGC neurons and their projecting axons, whilst the mature RGCs down-regulated their expression. Nogo-A in the new born RGCs might play some cell-intrinsic roles such as decreasing axon branching in vivo.