Restricted Migration of Transplanted Oligodendrocytes or their Progenitors, Revealed by Transgenic Marker MβP

Transgenic mice of line MβP3 express bacterial β-galactosidase in oligodendrocytes but not other cells of the CNS. The marker enzyme, demonstrated histochemically or by immunostaining in oligodendrocyte cell bodies and along myelin internodes, appears at the time of myelination and persists thereafter; in transplantation experiments, the marker may serve to indicate both the source of particular cells and their state of differentiation. The subventricular zone of the lateral ventricle, grafted from transgenic to wild-type perinatal recipient mice, yields histochemically labeled oligodendrocytes in surrounding host tissue. When grafts are placed in cerebral cortex near callosal radiations, graft-derived oligodendrocytes are found in cerebral cortex and subcortical white matter as far as 1.5 mm from the site of implant but not in nearby caudoputamen. This study is the first to document differentiation of transplant-derived oligodendrocytes in normal developing CNS. Our results are consistent with the well- established notion that oligodendrocyte progenitors migrate during normal development and suggest that such migration might be guided or restricted by mechanisms yet to be identified.