Fig. 7. Ectopic Wnt1 expression in the telencephalon produced heterotopias identical to those seen in Emx2^–/– mice. (A-C) Representative histological analysis (Hematoxylin and Eosin staining) of the 18.5 dpc cortex of Emx2^–/– (n=6) (B) and Wnt1-Tg (n=2) (C) mice demonstrated heterotopias that were identical in morphological appearance. A further Wnt1-Tg founder so analyzed at P1 also showed heterotopias. Lesions in the Wnt1-Tg mice contained NeuN-positive neurons (D, arrowheads) as well as calretinin-positive neuronal cell bodies and processes (F, arrowheads) similar to those seen in Emx2^–/– mice (E, arrowheads). Immunohistochemistry for Nestin demonstrated focal defects in the subpial glia limitans in direct association with heterotopias of Emx2^–/– (H) and Wnt1-Tg (I) mice, which were not seen in wild-type littermates (G). Staining was normal away from the lesions (red arrowheads). Radial glial processes (white arrowheads) were seen to extend directly into the lesions from the underlying cortical plate but did not form a glia limitans (H,I). mz, marginal zone; cp, cortical plate.