Rieger F, Daniloff J K, Pincon-Raymond M, Crossin K L, Grumet M, Edelman G M
J Cell Biol. 1986 Aug;103(2):379-91. doi: 10.1083/jcb.103.2.379.
Immunocytochemical methods were used to show that Ng-CAM (the neuron-glia cell adhesion molecule), N-CAM (the neural cell adhesion molecule), and the extracellular matrix protein cytotactin are highly concentrated at nodes of Ranvier of the adult chicken and mouse. In contrast, unmyelinated axonal fibers were uniformly stained by specific antibodies to both CAMs but not by antibodies to cytotactin. Ultrastructural immunogold techniques indicated that both N-CAM and Ng-CAM were enriched in the nodal axoplasm and axolemma of myelinated fibers as well as within the nodal regions of the myelinating Schwann cell. At embryonic day 14, before myelination had occurred, small-caliber fibers of chick embryos showed periodic coincident accumulations of the two CAMs but not of cytotactin, with faint labeling in the axonal regions between accumulations. Cytotactin was found on Schwann cells and in connective tissue. By embryonic day 18, nodal accumulations of CAMs were first observed in a few medium- and large-caliber fibers. Immunoblot analyses indicated that embryonic to adult conversion of N-CAM and a progressive decrease in the amount of Ng-CAM and N-CAM occurred while nodes were forming. Sciatic nerves of mouse mutants with defects in cell interactions showed abnormalities in the distribution patterns and amount of Ng-CAM, N-CAM, and cytotactin that were consistent with the known morphological nodal disorders. In trembler (+/Tr), intense staining for both CAMs appeared all along the fibers and the amounts of N-CAM in the sciatic nerve were found to be increased. In mice with motor endplate disease (med/med), Ng-CAM and N-CAM, but not cytotactin, were localized in the widened nodes. Both trembler and med/med Schwann cells stained intensely for cytotactin, in contrast to normal Schwann cells which stained only slightly. All of these findings are consistent with the hypothesis that surface modulation of neuronal CAMs mediated by signals shared between neurons and glia may be necessary for establishing and maintaining the nodes of Ranvier.
免疫细胞化学方法被用于显示神经胶质细胞黏附分子（Ng-CAM）、神经细胞黏附分子（N-CAM）以及细胞外基质蛋白细胞接触蛋白在成年鸡和小鼠的郎飞结处高度富集。相比之下，无髓轴突纤维被两种细胞黏附分子（CAMs）的特异性抗体均匀染色，但未被细胞接触蛋白的抗体染色。超微结构免疫金技术表明，N-CAM和Ng-CAM在有髓纤维的节段轴质和轴膜以及髓鞘形成雪旺细胞的节段区域中均有富集。在胚胎第14天，在髓鞘形成之前，鸡胚的小口径纤维显示出两种细胞黏附分子的周期性同步积累，但细胞接触蛋白没有，在积累之间的轴突区域有微弱标记。细胞接触蛋白存在于雪旺细胞和结缔组织中。到胚胎第18天，首次在一些中口径和大口径纤维中观察到细胞黏附分子的节段积累。免疫印迹分析表明，在节点形成过程中，N-CAM从胚胎期向成年期转变，Ng-CAM和N-CAM的量逐渐减少。细胞相互作用存在缺陷的小鼠突变体的坐骨神经显示出Ng-CAM、N-CAM和细胞接触蛋白的分布模式和量的异常，这与已知的形态学节点紊乱一致。在颤抖小鼠（+/Tr）中，两种细胞黏附分子的强烈染色出现在整个纤维上，并且发现坐骨神经中N-CAM的量增加。在患有运动终板疾病（med/med）的小鼠中，Ng-CAM和N-CAM，而非细胞接触蛋白，定位于增宽的节点。与仅轻微染色的正常雪旺细胞相比，颤抖小鼠和med/med小鼠的雪旺细胞对细胞接触蛋白均有强烈染色。所有这些发现都与以下假设一致，即神经元和神经胶质细胞之间共享的信号介导的神经元细胞黏附分子的表面调节可能是建立和维持郎飞结所必需的。
