Levine J M, Card J P
J Neurosci. 1987 Sep;7(9):2711-20. doi: 10.1523/JNEUROSCI.07-09-02711.1987.
Immunofluorescence and immunoperoxidase techniques were used to localize a cell surface chondroitin-sulfate proteoglycan antigen, termed NG2, in the developing and adult rat cerebellum. In the adult, both polyclonal and monoclonal anti-NG2 antibodies labeled cells throughout the cerebellar cortex, with the labeled cells being especially prominent in the molecular layer. The labeled cells had small, irregularly shaped cell bodies from which thin highly branched processes radiated in a stellate array. The NG2-labeled cells were not labeled with antibodies against glial fibrillary acidic protein (GFAP), vimentin, or S-100 protein, intracellular markers for astrocytes. However, electron microscopic immunocytochemical analysis of NG2 immunoreactive cells revealed a cell morphology consistent with that of protoplasmic astrocytes. Labeled cell bodies contained a thin rim of organelle-poor cytoplasm surrounding a euchromatic nucleus. Thick processes originating from the cell soma tapered to form thin branches with highly irregular surface contours that extended between adjacent neuronal elements. The labeled processes did not form synapses in the neuropil, and no synaptic profiles onto anti-NG2-labeled cell bodies or processes were observed. Thus, we conclude that the NG2 antigen is a cell surface marker for a class of smooth protoplasmic astrocytes. Immunoreactive cells were seen in the developing cerebellum beginning at embryonic day 16. The number of labeled cells increased during the early stages of cerebellar development, reaching a peak at about postnatal day (PND) 4 or 5 and declining thereafter. In the developing cerebellum, labeled cells lying within the forming molecular layer resembled the cells seen in the adult, whereas cells lying deeper within the folia had an immature appearance with fewer processes and less branching. This apparent gradient of morphological maturation suggests that an interaction with parallel fibers in the developing molecular layer may play a role in the terminal cytodifferentiation of the NG2-labeled smooth protoplasmic astrocytes.
免疫荧光和免疫过氧化物酶技术被用于在发育中和成年大鼠小脑中定位一种细胞表面硫酸软骨素蛋白聚糖抗原，称为NG2。在成年大鼠中，多克隆和单克隆抗NG2抗体标记了整个小脑皮质中的细胞，标记细胞在分子层中尤为突出。标记细胞具有小的、形状不规则的细胞体，从这些细胞体中伸出薄的高度分支的突起，呈星状排列。NG2标记的细胞未被针对胶质纤维酸性蛋白（GFAP）、波形蛋白或S-100蛋白（星形胶质细胞的细胞内标记物）的抗体标记。然而，对NG2免疫反应性细胞的电子显微镜免疫细胞化学分析显示，其细胞形态与原浆性星形胶质细胞一致。标记的细胞体含有围绕常染色质核的一层薄的、细胞器稀少的细胞质。源自细胞体的粗大突起逐渐变细，形成具有高度不规则表面轮廓的细分支，这些分支在相邻神经元之间延伸。标记的突起在神经毡中不形成突触，也未观察到针对抗NG2标记的细胞体或突起的突触结构。因此，我们得出结论，NG2抗原是一类光滑原浆性星形胶质细胞的细胞表面标记物。在胚胎第16天开始在发育中的小脑中可见免疫反应性细胞。在小脑发育的早期阶段，标记细胞的数量增加，在出生后第（PND）4或5天左右达到峰值，此后下降。在发育中的小脑中，位于形成中的分子层内的标记细胞类似于成年期所见的细胞，而位于小叶更深层的细胞外观不成熟，突起较少且分支较少。这种明显的形态成熟梯度表明，与发育中的分子层中的平行纤维相互作用可能在NG2标记的光滑原浆性星形胶质细胞的终末细胞分化中起作用。
