Figure 7.
Radial glia give rise to ependymal cells. A, B, Schematic depicting the injection site in the ventrolateral striatum at P0 (A) and the resulting labeling pattern at P2 (B). Injection of an adenovirus expressing Cre recombinase results in labeling of infected cells in mice that report Cre recombination with either lacZ (R26R mice) or eGFP (Z/EG mice). Radial glia are infected at their long processes that pass through the striatal injection site. C, The only labeled cells in the VZ are radial glia (region from box in B) for which cell bodies appear to undergo interkinetic nuclear migration (arrow). LV, Lateral ventricle. D, At P4, radial glia in the lateral ventricular wall do not express S100β or only express it very weakly (arrows), although expression is strong in the medial wall. In this example, the ventricle collapsed during histological processing so the medial and lateral walls are touching (dotted line), allowing for direct comparison of S100β expression. Some S100β+ cells have radial processes, suggesting that they are derived from cells with radial processes. These cells can be seen on both the medial (arrowhead) and lateral (data not shown) ventricular walls. E, F, Intermediate radial glia-ependymal stages. Cells with radial glial morphology, including a long radial process (F, arrows), express the ependymal cell marker CD24 and are beginning to produce cilia (arrowhead). The basal bodies from which these cilia form (E, boxed region) are surrounded by X-gal precipitate in R26R animals injected with Ad:Cre at P0 (E, arrows). This demonstrates that immature multiciliated cells in the lateral ventricular wall are derived from radial glia and suggests that basal bodies were associated with deuterosomes derived from the nuclear membrane, where the X-gal precipitate is normally found. G, H, Radial glia give rise to mature ependymal cells. By P30, animals injected with Ad:Cre at P0 in the ventrolateral striatum have ependymal cells in the lateral wall of the lateral ventricle. These cells were localized in a patch in the same region where radial glia were originally labeled. In injected R26R animals, these cells have X-gal precipitate surrounding the nucleus and the basal bodies (G, arrowheads) and have the ultrastructural characteristics of mature ependymal cells including a light cytoplasm, round nucleus, cilia (G, arrow), and microvilli (G, asterisk). In injected Z/EG animals, these cells coexpress GFP (H, arrows) and S100β (H, arrowheads) throughout their cell bodies, including their cilia.