Fig. 1. Marginal zone heterotopias in Emx2^–/– mice are similar to human heterotopias in individuals with cortical dysplasia. Histological analysis of Hematoxylin and Eosin stained sections from Emx2^–/– mouse brains demonstrated diffuse changes in the marginal zone with increased cellularity and poor distinction of the marginal zone from the underlying cortical plate proper (D-F). Nodular protrusions of cells into the marginal zone and overlying leptomeninges (arrowheads) were also detected and were frequently associated with focal disorganization of the subplate and full thickness abnormalities of the cortical plate in the same regions (broken line). No such abnormalities were detected in Emx2^+/– littermates (A-C). Hematoxylin and Eosin stained human leptomeningeal glioneuronal heterotopia from the cortex of a 36-week-old human infant had a similar morphology (G). Immunohistochemical analysis of human and Emx2^–/– lesions demonstrated the presence of NeuN-positive neurons within both lesions (H,J arrows). Immunohistochemistry in the human (I) and in situ hybridization in the mouse (K) demonstrated GFAP-positive astrocytes within the lesions (arrowheads). mz, marginal zone; cp, cortical plate; sp,subplate; iz, intermediate zone. Scale bar: in G, 200 µm for G; in C, 50 µm for C,F,J,K.