Fig. 3. Abnormal differentiation in Vax1^-/- brains. Proliferating cells at E13.5 (A,B) and E16.5 (C,D) were revealed with anti-Ki67 antibody. Ki67 shows strong labeling in the VZ and SVZ of the wild-type LGE and MGE (A,C). Labeling in the Vax1 mutant is significantly expanded in the MGE and presumptive septal area (D). The expansion of the VZ in the mutant MGE is confirmed by the complementary Tuj1 staining at E15.5 (E,F). There is strong expansion of the Tuj1-negative domain in the mutant brain (F). (G,H) Birthdating analysis. Brains were injected with BrdU at E13.5 and analyzed at P0. Cells labeled with BrdU at E13.5 are dispersed in the wild-type P0 brain (G, arrowheads); by contrast, BrdU-positive cells linger at the border between proliferating and differentiated regions in the mutant MGE (H, arrowheads). Acb, nucleus accumbens; Acb^*, presumptive nucleus accumbens; LGE, lateral ganglionic eminence; MGE, medial ganglionic eminence; SA, septal area; SA^*, presumptive septal area; VZ, ventricular zone. Scale bars: 500 µm in A-F; 100 µm in G,H.