Tbr2 is expressed by NS-div IPCs. A-S, Confocal images of coronal sections through E14.5 cortex. A-D, Tbr2 (red) and BrdU (green). The bracketed area in A is shown in separate color channels in B-D. Tbr2 was expressed by most S-phase cells in the SVZ and some in the VZ (arrowheads in B-D). E-G, Tbr2 (red) and DNA (blue). Tbr2 was expressed by NS-div cells (red arrowhead in E-G) but not by S-div cells (green arrowheads). H-J, Tbr2 (red) was expressed by phosphovimentin⁺ (p-vim) M-phase cells (green) in the SVZ (arrowheads). K-M, Tbr2 (red) and PCNA (green). Most Tbr2⁺ cells contained PCNA, including mitotic figures (arrowheads). N, Tbr2 (red) and nestin (green). Most Tbr2⁺ cells (arrowheads) appeared to lack nestin. O, Tbr2 (red) and βIII-tubulin (β-tub; green). Most Tbr2⁺ cells (arrowheads) lacked βIII-tubulin. P-S, Tbr2 (red), NeuN (green), and DNA (blue). The bracketed area in P is enlarged and shown in separate color channels in Q-S. Most Tbr2⁺ cells did not express NeuN, but those that did included some mitotic figures (arrowheads in Q-S). T-V, E14.5 cortical cells cultured for 1 d in vitro, labeled to detect Tbr2 (red), DNA (blue), and, in green, nestin (T), βIII-tubulin (U), or NeuN (V). Few Tbr2⁺ cells expressed nestin (5.1%) or βIII-tubulin (12.7%), but more expressed NeuN (20.8%; arrowheads). Scale bars: (in A) A-D, P, 50 μm; (in E) E-G, 20 μm; (in H) H-J, Q-S, 10 μm; (in K) K-M, O, 10 μm; (in N) N, 20 μm; (in T) T-V, 20 μm.