Late-born (E15.5) interneurons in Dab1 mutant brains show random distribution. A, Double-labeling for GABA (green) and BrdU (red) reveals that the vast majority of double-labeled cells (yellow) are in the upper layers of the wild-type cortex. B, Higher magnification of boxed area in A indicating that the majority of double-labeled interneurons (arrows) are in the upper layers of the cortex. C, Histogram depicting the layer positions of GABA–BrdU interneurons (n = 3 animals, 221 cells; mean ¶ SEM percentage) indicating that the majority of late-born interneurons in wild-type cortices are distributed in the upper layers. D, In Dab1 mutants, double-labeled interneurons (yellow) born at E15.5 are found in all layers of the cortex. E, F, Higher magnification of upper and lower (respectively) boxed areas in D indicating that double-labeled interneurons (arrows) are equally distributed to upper and lower layers of the Dab1 mutant cortex. G, Histogram depicting the layer positions of GABA–BrdU interneurons (n = 3 animals, 441 cells; mean ¶ SEM percentage) indicating that the late-born interneurons in Dab1 mutant cortices are randomly distributed throughout all layers of the cortex. Scale bar: A, D, 160 μm; B, E, F, 80 μm. WM, White matter.