Fig. 3. The developing cerebral cortex of the C3G^gt/gt mutant shows a failure of preplate splitting. (A,B) Confocal z-stack reconstruction of frozen sections of developing cerebral cortex of wild-type (A) and C3G^gt/gt mutant (B) mouse embryos treated with BrdU at E10.5 and recovered at E14.5. Note BrdU-positive cells on the pial side (arrows in A) and below (arrowheads in A) the early cortical plate in the wild type. By contrast, in the C3G^gt/gt developing cortex, BrdU-positive cells are almost exclusively found near the pial surface (arrows in B) and not in the area where the subplate would be expected (asterisk, B). (C,D) Calretinin staining (brown) of marginal zone cells (arrows) and subplate cells (arrowheads) in the wild-type (C) and C3G^gt/gt mutant (D) developing cortex. Note the absence in the mutant of subplate cells in a position below the marginal zone where the subplate would be expected (asterisk in D). (E,F) Developing cerebral cortex of wild-type (E) and C3G^gt/gt mutant (F) embryos treated with BrdU at E12.5 and recovered at E14.5. Note the position of the labelled wild-type cells of the future layer VI in the nascent cortical plate (arrows in E) in contrast to the disorganised position of the C3G^gt/gt mutant cells (arrows in F). Note that in this experiment some preplate cells were also labelled. Labels as in Fig. 1. Scale bar: 21 µm in A; 23 µm in B; 26 µm in C,D; 17 µm in E,F.