Fig. 1. Ventral tangential cell migration in organotypic culture. (A) Schematics of organotypic culture. A strip was dissected from the E10.5 mouse telencephalon along the dorsoventral axis to include the presumptive LOT area (green area) around the middle. A small area in the dorsal neocortex of the strip was labeled with fluorescent dye rhodamine (asterisk). (B) The strip 3 hours after preparation. Rhodamine-labeled cells (magenta) do not migrate yet from the labeled position (asterisk). Boundary between the neocortex and the GE is visualized by immunostaining against reticulon 1 (green). (C) The strip after 36 hours in culture. Merged image of rhodamine (magenta) and immunostaining with mAb lot1 (green). One of the rhodamine-labeled cells migrating ventrally reacts with mAb lot1 (arrowhead). (D,E) The strip after 2 days in culture. Many rhodamine-labeled cells (magenta in D, white in E) migrate in the ventral direction from the dye injection point (asterisk) and stop before entering the GE. Reticulon 1 is immunostained in green in D. (F,G) High-magnification views of the upper (F) and lower (G) boxes in E. The processes of many rhodamine-labeled cells are directed in the ventral direction in F, but reoriented in the rostrocaudal direction at the presumptive LOT area in G. Left, rostral aspect; top, dorsal aspect; dcx, dorsal neocortex; vcx, ventral neocortex; GE, ganglionic eminence. Scale bars: 500 µm in B,D; 50 µm in C,F,G.