Fig. 3. Abnormal morphology and migration of granule cells in microexplant cultures of the Pax6 mutant (rSey²/rSey²) EGL. (A,B) Transmission electron micrographs of the EGL cells in culture (3 DIV). Spindle-shaped granule cell has long, thick leading process associated with preformed neurites of other cells in the wild-type culture (A). Pax6 mutant cells are round in morphology and form short thin processes attached to (arrow) or detached from (arrowhead) neighboring cells (B). (C,D) Phase-contrast light micrographs of EGL cells migrating from the explant (2 DIV). Colored lines are trajectories of the granule cells traced for 8 hours. While wild-type cells extend long radial neurites and migrate along the fibers (C), Pax6 mutant cells lack long neurites and move randomly (D). (E,F) Pax6 expression. (G,H) TAG-1 expression. Wild-type cells extend TAG-1-positive long neurites (G), while mutant cells express TAG-1 around their cell bodies and in the short neurites (H). (I,J) MAP2 expression demarcates the leading processes of migrating neurons. (K,L) Differentiation of parallel fibers is shown by 440 kDa Ankyrin_B-positive staining in wild-type cells (K). Pax6 mutant cells express Ankyrin_B in irregularly aligned processes (L). Cultures were maintained for 40 hours (E-J) and 72 hours (K,L). Scale bars: 10 µm in A,B; 50 µm in C-L.