Fig. 6. Formation of astrocytes with GFAP upregulation in the superficial layers of the Olig2-ablated cortex. (A,B) Hematoxylin and Eosin (H/E) staining of sagittal sections of control (Ctrl^G) and Olig2-ablated (Cko^G) cortices at P14. Arrows indicate the superficial cortical layers. (C-F) Cortices of control and Cko^G mice at P14 were immunolabeled with antibodies against GS and GFAP. Arrows indicate GS⁺ cells (C,D) and GS GFAP co-expressing cells (F). (G-I) Cortices of control (G,H) and Cko^G (I) mice at P14 were immunostained with Olig2, S100ß and GFAP. Regions from superficial layers of the cortex are shown. Arrows in G indicate cells co-labeled with Olig2 and S100ß. Arrows in H,I indicate S100ß⁺ in the control and S100ß GFAP co-expressing cells in the Olig2 mutant, respectively. (J) Bar chart showing the average number of GS⁺ and S100ß⁺ cells per unit area (0.1 mm²) in the superficial layers of control and Olig2 mutant (Cko) mice (>400 cells counted, n=3); bars indicate s.d. (K-M) Cortices of control and Cko^G animals at P14 were immunolabeled with GFAP (K-M), Ki67 (M) and BrdU (K,L) after a 4-hour pulse of BrdU administration before sacrifice. Arrows indicate BrdU⁺ and Ki67⁺ cells in the cortex, respectively. (N) Bar chart indicating the gross number of BrdU⁺ cells per field (0.4 mm²) in the superficial layers of control and Olig2- ablated (Cko) cortices (>200 cells counted, n=3) at P7 and P14; bars indicate s.d. (O,P) Immunostaining of Ki67 in the SVZ of the control (O) and Olig2 mutant (P) brains. Scale bars: 100 µm.