Figure 6. Fate analysis of LCMV-infected cells at different developmental stages. A, Proportions (indicated as averages ± SEMs) of mature phenotypes generated at P30 by LCMV-infected progenitors at different stages during the embryonic (E15), early (P1), and later (P5) postnatal development. B, LCMV injected in the fourth ventricle transduces RG cells lining the ventricular surface (arrow). Both interneurons (arrows and arrowhead in C–E, I, J, M) and glial cells (arrows in F–H, K, L, N) derive from LCMV-infected cells but to various extents during development. Different categories of interneurons are recognized by their morphology, location in the cerebellar cortex, and expression of typical markers (C–E, I, J, M). C, I, Pax2+ Golgi cells in the GL originate from early progenitors (E15, P1). D, E, J, M, Postnatally infected progenitors mainly generate interneurons of the most superficial layers (arrows). PV+ basket cells settle close to Purkinje cell somata that they contact by means of specialized axonal terminals (i.e., the pinceau; see arrowheads in E, J). OLs in the ML (F, arrows) and the WM (G, arrows) are found exclusively after early infections, in addition to parenchymal astrocytes (H, arrows) and BG (H, arrowhead). Postnatal injections give rise to GFAP+ astrocytes of the WM (arrows in K, N) and more rarely to BGs (L, arrows). Pixels decorated by positivity for both GFP and GFAP are represented in white in L. O, No Olig2+ OLs are observed after P5 infections. Results in A are indicated as averages of proportions ± SEMs (E15, P5 n = 3; P1 n = 5). DCN, Deep cerebellar nuclei. Scale bars, 20 μm.