Fig. 7. The dispersal of oligodendrocyte precursors from the ventral ventricular zone is dependent on netrin. (A) Stage 28 chick spinal cord slice labeled with O4 antibody 1 hour after dissection showed minimal staining in the ventral ventricular zone. (B) After 24 hours O4-positive oligodendrocyte precursors showed ventral radial migration, which increased over the next 24 hours (C) (48 hours total). (D) The majority of migrating cells have immature unipolar or bipolar cell morphology. (E) In the presence of anti-DCC antibodies, O4-positive cells have a smaller cell body and more processes. (F) The migration of O4-positive oligodendrocyte precursors is inhibited in the presence of anti-DCC antibody with the majority of O4-positive cells remaining in the ventral spinal cord. (G) Addition of exogenous chick netrin 1 to the slices also inhibits oligodendrocyte precursor migration. (H) Normal mouse IgG did not disrupt oligodendrocyte precursor migration, neither did anti-prion antibody (I). (J) Anti-NCAM antibody altered the pattern of migration, but did not mimic the changes seen with anti-DCC or netrin 1. (K-O) Stage 31 chick spinal cord slices. (K) Stage 31 spinal cord slice after dissection showed ventral radial migration. (L) Spinal cord slices grown in the presence of anti-DCC antibody or chick netrin 1 ligand (N) did not show an altered migration pattern compared with controls (M,O) suggesting that more mature oligodendrocyte precursors are less sensitive to netrin 1. Scale bars: in C, 100 µm for A-C,F-J; in E, 10 µm for D,E; in K, 100 µm for K-O.