Shibata T, Yamada K, Watanabe M, Ikenaka K, Wada K, Tanaka K, Inoue Y
Department of Anatomy, Hokkaido University School of Medicine, Sapporo 060, Japan.
J Neurosci. 1997 Dec 1;17(23):9212-9. doi: 10.1523/JNEUROSCI.17-23-09212.1997.
The glutamate transporter GLAST is localized on the cell membrane of mature astrocytes and is also expressed in the ventricular zone of developing brains. To characterize and follow the GLAST-expressing cells during development, we examined the mouse spinal cord by in situ hybridization and immunohistochemistry. At embryonic day (E) 11 and E13, cells expressing GLAST mRNA were present only in the ventricular zone, where GLAST immunoreactivity was associated with most of the cell bodies of neuroepithelial cells. In addition, GLAST immunoreactivity was detected in radial processes running through the mantle and marginal zones. From this characteristic cytology, GLAST-expressing cells at early stages were judged to be radial glia cells. At E15, cells expressing GLAST mRNA first appeared in the mantle zone, and GLAST-immunopositive punctate or reticular protrusions were formed along the radial processes. From E18 to postnatal day (P) 7, GLAST mRNA or its immunoreactivity gradually decreased from the ventricular zone and disappeared from radial processes, whereas cells with GLAST mRNA spread all over the mantle zone and GLAST-immunopositive punctate/reticular protrusions predominated in the neuropils. At P7, GLAST-expressing cells were immunopositive for glial fibrillary acidic protein, an intermediate filament specific to astrocytes. Therefore, the glutamate transporter GLAST is expressed from radial glia through astrocytes during spinal cord development. Furthermore, the distinct changes in the cell position and morphology suggest that both the migration and transformation of radial glia cells begin in the spinal cord between E13 and E15, when the active stage of neuronal migration is over.
谷氨酸转运体GLAST定位于成熟星形胶质细胞的细胞膜上，在发育中脑的脑室区也有表达。为了在发育过程中表征和追踪表达GLAST的细胞，我们通过原位杂交和免疫组织化学对小鼠脊髓进行了检查。在胚胎第11天（E11）和第13天（E13），表达GLAST mRNA的细胞仅存在于脑室区，GLAST免疫反应性与神经上皮细胞的大多数细胞体相关。此外，在穿过套层和边缘区的放射状突起中检测到GLAST免疫反应性。根据这种特征性细胞学，早期表达GLAST的细胞被判定为放射状胶质细胞。在E15时，表达GLAST mRNA的细胞首次出现在套层区，并且沿放射状突起形成了GLAST免疫阳性的点状或网状突起。从E18到出生后第7天（P7），GLAST mRNA或其免疫反应性从脑室区逐渐减少，并从放射状突起中消失，而带有GLAST mRNA的细胞遍布套层区，GLAST免疫阳性的点状/网状突起在神经毡中占主导。在P7时，表达GLAST的细胞对胶质纤维酸性蛋白呈免疫阳性，胶质纤维酸性蛋白是星形胶质细胞特有的中间丝。因此，谷氨酸转运体GLAST在脊髓发育过程中从放射状胶质细胞到星形胶质细胞均有表达。此外，细胞位置和形态的明显变化表明，放射状胶质细胞的迁移和转变均始于E13至E15之间的脊髓，此时神经元迁移的活跃阶段已经结束。
