Fig. 4. Non cell-autonomous effect on cortico-striatal cell migration in ngn2^lacZ/ngn2^lacZ mice. (A) Example of a homotypic transplantation of a small piece of cortex from a ‘green mouse’ (Okabe et al., 1997) on a ngn2^–/– E14 cortex slice fixed after 1 day in vitro. Note that most GFP cells have migrated within the cortex and some of them have crossed the boundary (dashed line) into the GE (arrows). (A’) High power view of part of the explant shown in A (see arrows for reference). (B) Quantification of the cells emigrating from transplants of wild-type cortex on slices from wild-type or ngn2^–/– littermates. Note that the overall number of migrating cells, as well as the number of cortical cells entering the GE, is higher on a ngn2^–/– substratum compared to wild type. (C) The histogram depicts the proportion of all cells emigrating from the cortex transplants that enter the GE (see B). Note that three times as many migrating cells cross the boundary into the GE on a ngn2^–/– substratum than on a wild-type substratum.