EARLY DEVELOPMENT OF THE OLIGODENDROCYTE IN THE EMBRYONIC CHICK METENCEPHALON

It has been demonstrated that the spinal cord oligodendrocytes in the vertebrates arise in the ventral ventricular zone adjacent to the floo r plate in their early development. Because of the similarities of bas ic structures in the spinal cord and metencephalon, it is probable tha t the mode of early oligodendrocyte development in the metencephalon i s the same as that in the spinal cord. We examined this possibility in chick embryos, using monoclonal antibodies O1 and O4, markers for oli godendrocyte lineage, An O4-positive (O4+) cell focus was observed in the medial ventricular zone of E5 chick ventral metencephalon (the ear liest stage examined), adjacent to the floor plate, At E6, O4+ cells w ere dispersed from the medial to the lateral pens and, at E7, to the c erebellar anlagen, O4+ cells in the E6 brainstem and in the E7 cerebel lum were unipolar in shape, whereas one day later, some of the labeled cells were multipolar with a few thin processes, O1+ oligodendrocytes first appeared at E8 in the ventromedial part of the pens and were di stributed throughout the pens at E10 and in the cerebellum at E12, Exp lants from three subdivisions of the metencephalon (medial and lateral pens, and cerebellum) from E5 to E8 chick embryos were separately cul tured to confirm the potential for generation of oligodendrocyte linea ge, O4+ cells appeared in the culture of the E5 medial pens (the earli est stage examined), in the E6 lateral pens, and in the E7 cerebellum, In addition, E7 was the youngest stage from which cerebellar explants were able to generate O1+ oligodendrocytes, Our results clearly demon strated the in vivo morphology of oligodendrocyte precursors in the me tencephalon and their developmental appearance in a ventral-to-dorsal manner, From the bipolar morphology of O4+ cells and the spacio-tempor al continuity of the dispersion, it is inferred that the initial dispe rsion of O4+ cells may involve oligodendrocyte migration from the focu s of the medial pens to the lateral and dorsal parts of the metencepha lon. (C) 1997 Wiley-Liss, Inc.