Fig. 3. Astrocyte differentiation deficit in the white matter of the Olig2-ablated cortex. (A-D) Expression of GFAP (Red) and Olig2 (green) was analyzed by immunohistochemistry on coronal brain sections of control (A,C) and Olig2-ablated (B,D) mice at P14. Arrowheads indicate white matter. (E,F) Hematoxylin and Eosin (H/E) staining of sagittal sections of control (Ctrl^G) and Olig2-ablated (Cko^G) cortices at P14. (G,H) Cortices of control (Ctrl^G) and Olig2 mutant (Cko^G) mice at P14 were immunostained with an anti-S100ß antibody. Arrowheads in E-H indicate the corpus callosum (CC). (I-N) Double immunostaining of glutamine synthetase (GS, red) and GFAP (green) in the corpus callosum (arrowheads) of wild-type (I,J), Ctrl^G (K,L) and Olig2 mutant (Cko^G; M,N) mice. GS⁺ and GS⁺ GFAP⁺ cells are shown in I,K,M and J,L,N, respectively. (O) Bar chart showing the average number of GS⁺ and S100ß⁺ cells per unit area (0.1 mm²) in the corpus callosum of wild-type (wt), Ctrl^G and Olig2 mutant (Cko^G) mice (>300 cells counted, n=3); bars indicate s.d. Scale bars: 100 µm in A-D; 100 µm in G,H; 50 µm in I-N.