Gray G E, Sanes J R
Department of Anatomy and Neurobiology, Washington University School of Medicine, St Louis, MO 63110.
Development. 1992 Jan;114(1):271-83. doi: 10.1242/dev.114.1.271.
In many parts of the central nervous system, the elongated processes of radial glial cells are believed to guide immature neurons from the ventricular zone to their sites of differentiation. To study the clonal relationships of radial glia to other neural cell types, we used a recombinant retrovirus to label precursor cells in the chick optic tectum with a heritable marker, the E. coli lacZ gene. The progeny of the infected cells were detected at later stages of development with a histochemical stain for the lacZ gene product. Radial glia were identified in a substantial fraction of clones, and these were studied further. Our main results are the following. (a) Clones containing radial glia frequently contained neurons and/or astrocytes, but usually not other radial glia. Thus, radial glia derive from a multipotential progenitor rather than from a committed radial glial precursor. (b) Production of radial glia continues until at least embryonic day (E) 8, after the peak of neuronal birth is over (approximately E5) and after radial migration of immature neurons has begun (E6-7). Radial glial and neuronal lineages do not appear to diverge during this interval, and radial glia are among the last cells that their progenitors produce. (c) As they migrate, many cells are closely apposed to the apical process of their sibling radial glia. Thus, radial glia may frequently guide the migration of their clonal relatives. (d) The population of labelled radial glia declines between E15 and E19-20 (just before hatching), concurrent with a sharp increase in the number of labelled astrocytes. This result suggests that some tectal radial glia transform into astrocytes, as occurs in mammalian cerebral cortex, although others persist after hatching. To reconcile the observations that many radial glia are present early, that radial glia are among the last offspring of a multipotential stem cell, and that most clones contain only a single radial glial cell, we suggest that the stem cell is, or becomes, a radial glial cell.
在中枢神经系统的许多部位，人们认为放射状胶质细胞的细长突起可引导未成熟神经元从脑室区迁移至其分化位点。为了研究放射状胶质细胞与其他神经细胞类型的克隆关系，我们使用重组逆转录病毒，用一种可遗传标记物——大肠杆菌β-半乳糖苷酶基因，来标记鸡视顶盖中的前体细胞。在发育后期，通过对β-半乳糖苷酶基因产物进行组织化学染色来检测受感染细胞的后代。在相当一部分克隆中鉴定出了放射状胶质细胞，并对其进行了进一步研究。我们的主要结果如下：(a) 包含放射状胶质细胞的克隆通常也含有神经元和/或星形胶质细胞，但通常不包含其他放射状胶质细胞。因此，放射状胶质细胞源自多能祖细胞，而非已定向分化的放射状胶质前体细胞。(b) 放射状胶质细胞的产生至少持续到胚胎第8天，此时神经元生成高峰期已过（约胚胎第5天），未成熟神经元的放射状迁移也已开始（胚胎第6 - 7天）。在此期间，放射状胶质细胞和神经元谱系似乎并未分化，放射状胶质细胞是其祖细胞产生的最后一批细胞之一。(c) 在迁移过程中，许多细胞紧密附着于其同胞放射状胶质细胞的顶端突起。因此，放射状胶质细胞可能经常引导其克隆亲属的迁移。(d) 在胚胎第15天至第19 - 20天（即将孵化前）之间，标记的放射状胶质细胞数量减少，同时标记的星形胶质细胞数量急剧增加。这一结果表明，一些顶盖放射状胶质细胞会转变为星形胶质细胞，就像在哺乳动物大脑皮层中发生的那样，尽管其他一些放射状胶质细胞在孵化后仍会持续存在。为了协调以下观察结果：早期存在许多放射状胶质细胞，放射状胶质细胞是多能干细胞的最后一批后代之一，且大多数克隆仅包含单个放射状胶质细胞，我们认为干细胞是或会变成放射状胶质细胞。
