Fig. 5. Transplantation analysis of migration defects. To determine that migration defects in Emx1/2 double mutants do not reside in ganglionic eminence cells, three assays were conducted (A). In the first assay (1), E13.5 medial ganglionic eminences were dissected and dispersed with trypsin. Then, the dispersed cells were labeled with DiI and injected into E13.5 medial ganglionic eminence of the host telencephalon slices. The donor cells were also BrdU-labeled, by injecting the drug into the pregnant mother intraperitoneally at E11.5, to rule out the possible secondary DiI-staining of host cells. BrdU-positive donor cells in the cortex were detected by immunohistochemical staining with the antibody against BrdU after vibratome sectioning. In the second assay (2), explants of about 150 µm diameter were prepared from E13.5 medial ganglionic eminences and labeled with DiI. The donor explant was placed into a hole cut through the medial ganglionic eminence of the E13.5 host telencephalic slice. In the third assay (3), cortices and medial ganglionic eminences were surgically separated obliquely (green line) at the lateral ganglionic eminence level. A wild-type cortex piece was then recombined with a mutant medial ganglionic eminence piece and vice versa. Subsequently, ganglionic eminence cells were labeled with either DiI or Venus. Venus is a EYFP variant (Nagai et al., 2002). The plasmid DNA solution was injected in the medial ganglionic eminences and introduced into the cells by electroporation (Marin et al., 2001). Typical examples of each assay are shown in B. Red arrows indicate the labeled cells in the front of migration; yellow dotted lines show the cortical/subcortical borders. Scale bars: 100 µm. (C) A summary odf the assay results. indicates the donor to host relationship. Each column of the table indicates the number of slices that showed the migration of donor ganglionic eminence cells into host cortex per total slices examined.