Bartsch U, Pesheva P, Raff M, Schachner M
Department of Neurobiology, Swiss Federal Institute of Technology, Zürich.
Glia. 1993 Sep;9(1):57-69. doi: 10.1002/glia.440090108.
We have analyzed the expression of the oligodendrocyte-derived extra-cellular matrix molecule janusin (previously termed J1-160/180) in the retina and optic nerve of developing and adult mice using indirect light and electron microscopic immunocytochemistry, immunoblot analysis, and enzyme-linked immunosorbent assay. In the optic nerve, janusin is not detectable in neonatal and only weakly detectable in 7-day-old animals. Expression is at a peak in 2- or 3-week-old animals and subsequently decreases with increasing age. In the retina, expression increases until the third postnatal week and then remains at a constant level. In immunocytochemical investigations at the light microscopic level, janusin was found in the myelinated regions of the nerve with spots of increased immunoreactivity possibly corresponding to an accumulation of the molecule at the nodes of Ranvier. At the electron microscopic level, contact sites between unmyelinated axons, between axons and glial cells, and between axons and processes of myelinating oligodendrocytes were immunoreactive. Cell surfaces of astrocytes at the periphery of the nerve and forming the glial-limiting membrane, in contrast, were only weakly immunopositive or negative. In cell cultures of young postnatal mouse or rat optic nerves, oligodendrocytes and type-2 astrocytes, but not type-1 astrocytes were stained by janusin antibodies. In the oligodendrocyte-free retina, janusin was detectable in association with neuronal cell surfaces, but not with cell surfaces of Müller cells or retinal astrocytes. Our observations indicate that expression of janusin in the optic nerve and in the retina is developmentally differentially regulated and that other cell types, in addition to oligodendrocytes, express the molecule. Since the time course of janusin expression in the optic nerve coincides with the appearance of oligodendrocytes and myelin and since janusin is associated with cell surfaces of oligodendrocytes and outer aspects of myelin sheaths and is concentrated at nodes of Ranvier, we suggest that janusin is functionally involved in the process of myelination.
我们运用间接光镜和电镜免疫细胞化学、免疫印迹分析以及酶联免疫吸附测定法，分析了少突胶质细胞衍生的细胞外基质分子janusin（先前称为J1-160/180）在发育中和成年小鼠视网膜及视神经中的表达情况。在视神经中，新生小鼠无法检测到janusin，7日龄动物中仅能微弱检测到。2至3周龄动物的表达达到峰值，随后随年龄增长而下降。在视网膜中，表达在出生后第三周前持续增加，之后保持恒定水平。在光镜水平的免疫细胞化学研究中，在神经的髓鞘区域发现了janusin，免疫反应性增加的斑点可能对应于该分子在郎飞结处的积累。在电镜水平，无髓鞘轴突之间、轴突与神经胶质细胞之间以及轴突与髓鞘形成少突胶质细胞的突起之间的接触部位具有免疫反应性。相比之下，神经外周形成胶质界膜的星形胶质细胞的细胞表面仅呈微弱免疫阳性或阴性。在新生小鼠或大鼠视神经的细胞培养物中，janusin抗体可对少突胶质细胞和2型星形胶质细胞染色，但对1型星形胶质细胞无染色。在无少突胶质细胞的视网膜中，可检测到janusin与神经元细胞表面相关，但与穆勒细胞或视网膜星形胶质细胞的细胞表面无关。我们的观察结果表明，janusin在视神经和视网膜中的表达在发育过程中受到不同调节，并且除少突胶质细胞外，其他细胞类型也表达该分子。由于janusin在视神经中的表达时间进程与少突胶质细胞和髓鞘的出现相吻合，并且janusin与少突胶质细胞的细胞表面以及髓鞘的外部相关，并集中在郎飞结处，我们认为janusin在髓鞘形成过程中发挥功能作用。
