Mechanisms of interkinetic nuclear migration Y Kosodo et al Figure 2 Arresting the cell cycle in G1-phase by introduction of p18Ink4c induces accumulation of nuclei in the basal region of the VZ. (A) Immunostaining of E14.5 mouse brain treated with p18Ink4c to arrest the cell cycle in G1-phase with a Ki67 antibody (proliferative marker, red). (a) Contralateral side. (b, b 0 ) E13.5 mouse lateral cortex in which p18Ink4c (b) and NLS-GFP (b0; green) were co-electroporated and incubated for 24 h. Bar ¼ 50 mm. (B) Expression of GFP (green) with electroporation of either control vector (a) or p18Ink4c (b, b0) into E10.5 mouse telencephalon followed by 18 h of whole-embryo culture. Immunostaining using a p18Ink4c antibody was performed (b0; red). Bar ¼ 10 mm. (C) Positions of NLS-GFP-expressing nuclei with control vector (a) or p18Ink4c (b) introduced by electroporation into E13.5 mouse cortex followed by a 24-h incubation. Co-staining using a Tuj1 antibody (neuronal marker, red) and DAPI (DNA, blue) was performed. Bar ¼ 10 mm. (D) Positions of NLS-GFP-expressing nuclei relative to the apical surface with control vector (a) or p18Ink4c (b). Sums of numbers (N, x-coordinate) counted in 15 electroporated brain sections (nuclei from each section are indicated by white or dotted boxes) are shown according to their distance from the apical surface (y-coordinate). For (A–C), apical surface is down. & 2011 European Molecular Biology Organization The EMBO Journal VOL 30 | NO 9 | 2011 1693