Fig. 1. Distribution of MGE cells one (E14.5, A-C), two (E15.5, D-F) and four (E17.5, G-I) days after homotopic transplantation. Coronal sections of embryonic mouse brains containing MGE cells labeled with PKH26 fluorescent dye before transplantation. Graft-derived cells are black or dark blue. (A) One day after transplantation, most of the grafted cells were located at the site of transplantation in the MGE. No grafted cells were detected in the lateral ventricle (lv). The pipette insertion site is marked by an arrow. (B) At 1 day post transplantation migrating cells were observed in the LGE and at the cortical boundary (arrowhead). (C) Example of a migratory cell with a leading process and a growth cone. (D) Two days after transplantation, multiple cells migrated into the neocortex. Migration is directional as no cells migrate to the septum (sep). (E) The highest density of migrating MGE cells is in the cortical subventricular zone. (F) Tangential section through the anterior neocortex reveals migrating cells in the subventricular zone (central lighter region). No graft-derived cells migrated into the olfactory bulb (ob). (G) Four days after transplantation, most of the MGE-derived cells settled in the neocortical marginal zone. No labeled cells were found in the hypothalamus (ht) and thalamus (th). (H) Cortical subventricular zone contains fewer migrating cells than at 2 days and most of the grafted cells are found in the marginal zone. (I) Disappearance of migrating neurons from the subventricular zone is obvious in the tangentially cut anterior cortex. Olfactory bulb is devoid of labeled cells.