Abstract FR:

This work examines the spatio-temporal development of the oligodendrocyte lineage in the bird embryo. The first part deals with the specification ofthe oligodendrocyte progenitors and the second part provides a study oftheir migration patterns. In the mouse the oligodendrocytes emerge from restricted and isolated territories along the neural tube which are characterised by the expression ofthe gene transcript plp/dm2O (Spassky et al 1998). My work consisted in the first instance in establishing if in the avian model the expression of the gene plp/dm2O also defines an oligodendrocyte lineage, as is the case in mammals. A comparative study has been carried out concerning the expression ofthe gene pip /dm2O as well as ofestablished markers ofthe oligodendrocyte lineage during the course ofthe embryonic development ofthe chick. This has allowed us to propose a map of ventricular foci of oligodendrogenesis and to show that oligodendrocyte emergence is very precocious and concomitant with the appearance of the first neurons. My studies have subsequently been directed towards the migration pathways of the oligodendrocyte precursors from their original focus. Using the system of embryonic chimerism between quail and chick and with the collaboration of I. Cobos and S. Martinez we have shown a subdivision of cerebral oligodendrocytes into a caudal population with radial and limited migration displaying a segmentary development, and a rostral population which is prosencephalic and shows extensive tangential migration.