FOCAL VENTRICULAR ORIGIN AND MIGRATION OF OLIGODENDROCYTE PRECURSORS INTO THE CHICK OPTIC-NERVE

During central nervous system (CNS) development, oligodendrocyte precu rsors originate in specific locations and subsequently migrate to all regions of the CNS. Here, we demonstrate that the chick optic nerve is populated by oligodendrocyte precursors, which initially appeared in a focal region at the ventral midline of the third ventricle at stage 26-27. Oligodendrocyte precursors migrated into the chiasmal end of th e nerve by stage 29 and became uniformly distributed by stage 35. Migr ating precursors were restricted to the anterior region of the nerve, closely apposed to axons, and had a bipolar morphology. In contrast to the polysialic acid (PSA)-dependent cooperative streaming migration o f olfactory neuronal precursors, the migration of oligodendrocyte prec ursors along the optic nerve appeared axophilic and unaffected by remo val of neural cell adhesion molecule (N-CAM)-associated PSA. These dat a indicate that during development, defined domains of the ventricular zone give rise to distinct cell types that utilize discrete mechanism s to navigate specific migrational pathways.