Fig. 7. Defects in gliogenesis in Pax6^-/- mutants. (A-E) Ectopic and precocious oligodendrogenesis in Pax6^-/- mice. The left and right sides of each panel show the staining of heterozygote (+/-) and homozygote (-/-) mice, respectively, at E13.5. Three horizontal lines indicate the dorsal limit of the Nkx6.1⁺ domain (upper), the ventral limit of the Irx3⁺ domain (middle), and the dorsal limit of the Nkx2.2⁺ domain (lower) in the heterozygote. The location of the normal Pax6⁺ domain is indicated by brackets. The reduced Olig2⁺ domain in the homozygous mutant is indicated by an arrow in B. Arrowheads indicate ectopic OLPs. (F,G) The numbers of ectopic Olig2⁺, Olig1⁺, and Nkx2.2⁺ cells in the MZ (F) and in the dorsal (normally Pax6⁺) VZ (G) in the Pax6^+/- and Pax6^-/- mice. Percentages are values relative to Pax6^+/- mice. Data are mean±s.d. obtained from staining of six to eight sections from two to three embryos for each genotype. ^**, P<0.01. (H,I) Premature astrogenesis in Pax6^-/- mice. In H, early astrocytes were detected as GS⁺ cells (arrowheads) at E15.5. In I, the number of GS⁺ cells detected per transverse section of the lumbar spinal cord is compared between Pax6^+/- (black bars) and Pax6^-/- (red bars) mice. (J) Schematic diagrams summarizing the defects in gliogenesis in Pax6^+/- mice. Notice that the generation of V0-2 interneurons is also defective in the mutant (Scardigli et al., 2001). Scale bars: 100 µm in E,H.