Fig. 3. The cortex contains an attractive activity for tangentially migrating cells derived from the MGE. (A) Schematic of the experimental paradigm used to quantify the migration of MGE-derived cells towards an ectopic cortex. (B) Migration of DiI labeled cells from the MGE (asterisk) after 48 hours in culture. Most cells migrate towards the ectopic cortex. (C) The number of DiI-labeled cells that migrated into the ipsilateral side of the slice (ipsi) or into the ectopic cortex (eNCx). The number of cells in the ipsilateral side includes those in the cortex and those en route towards the cortex (MGE and LGE). Total number of cells (n=18): 1590 (ipsi), 2582 (eNCx). Histograms show averages ±s.d. *P<0.001. (D) Schematic of the slice transplantation paradigm used to analyze the migration of MGE^GFP-derived cells when transplanted ectopically into the dorsal cortex. (E,F) Migration of MGE^GFP-derived cells (asterisk) after 48 hours in culture, labeled with GFP (E), and schematic representation of the routes followed by the MGE^GFP-derived cells (F). Note that cells fail to migrate into the more medial aspect of the embryonic hippocampus (i.e. the developing dentate gyrus and cortical hem; arrowhead in E, hatched region in F) (see also Polleux et al., 2002). (G) Schematic of the slice transplantation paradigm used to analyze the migration of MGE^GFP-derived cells towards an inverted dorsal cortex. (H,I) Migration of MGE^GFP-derived cells (asterisk) after 48 hours in culture, labeled with GFP (H), and schematic representation of the routes followed by the MGE^GFP-derived cells (I). The boxes shown in H (m and l) indicate the regions from which cell counting was made. eNCx, ectopic neocortex; H, hippocampus; L, lateral region of the dorsal cortex; LGE, lateral ganglionic eminence; M, medial region of the dorsal cortex; MGE, medial ganglionic eminence; NCx, neocortex; PCx, piriform cortex; POa, preoptic area; Str, striatum. Scale bars: 300 µm.