Fig. 2. Proliferation, interkinetic nuclear migration and orientation of cell division in wild-type and laminin 1III4^-/- cortex at midneurogenesis. Fluorescent micrographs of E14 wild-type and laminin 1III4^-/- cortex immunostained as indicated (A,B,E-H) reveal similar numbers of precursors (Ki67-positive) in mitosis (PH3-positive) at the ventricular surface (VS, arrowheads in A) or at abventricular positions. Ectopic clusters of precursor cells within the laminin 1III4^-/- cortical plate (CP) are indicated by arrows in B. (C) Histogram depicting the percentages of precursors dividing at the ventricular surface (VZ in C), subventricular zone (SVZ) or at ectopic positions assessed by the quantification of PH3-positive cells at E14 (wild type: n=40 sections, two animals, laminin 1III4^-/-: n=45, two animals). (D) Histogram depicting the number of PH3-positive cells per cortex area (100 µm²) dividing at VZ or SVZ positions respectively (wild type: n=43, two animals; laminin 1III4^-/-: n=51, two animals). (E-H) BrdU-immunostaining (red) reveals cells in S phase (0.5 hours after BrdU-injection; E,F) and 6 hours after S-phase labelling when they have moved towards the ventricular surface (G,H). (I) A dividing cell in anaphase labelled with propidium iodide. The angle of cell division was assessed by measuring the angle between a line at the VS and the separating chromatids. (J) Histogram depicting the percentages of cells dividing horizontally with respect to the VS (0-30°), obliquely (30-60°) and perpendicularly (60-90°) in E14 cortex (wild type: n=103 mitoses, two animals; laminin 1III4^-/-: n=110, two animals). Scale bars: 100 µm