(A) Schematic representation of the stratification of the VZ/SVZ, intermediate zone (IZ) and cortical plate (CP) in the E13.5 embryonic cortex. Molecular markers, expressed by the respective cell types are represented on the right side of the scheme. (B–D) Immunofluorescence analyses on sections of Khdrbs1+/+and Khdrbs1-/- brain from E13.5 embryos treated for 2 hr with BrdU to label proliferating cells. Sections were stained with anti-PAX6 (B), anti-TBR2 (C) or anti-TBR1 (D). All sections were co-stained with anti-BrdU antibody. Bar graphs on the right side show the number of BrdU/PAX6 (B), BrdU/TBR2 (C) and TBR1 (D) positive cells counted in 100 μm2. N = 3; ***p<0.001. Scale bar = 100 µm. SVZ, Subventricular Zone; VZ, Ventricular Zone; IZ, Intermediate Zone; CP, Cortical Plate; RGCs, Radial Glia Cells; IPCs, Intermediate Progenitor Cells.