Myelin-forming oligodendrocytes of developing mouse spinal cord: immunocytochemical and ultrastructural studies

The development and differentiation of oligodendrocytes (OC) in developing mouse spinal cord (MSC) were investigated by correlative analysis of light and electron microscopy (EM), and immunoperoxidase studies for glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP). The sequential development of glial cells within the subpial region of the MSC bears a striking resemblance to the developing human fetal spinal cord. A rise in the level of mitotic activity among subpial astrocytes just prior to the onset of myelination was followed by the appearance of OC within the same region. The finding of "transitional" cells with the cytological and ultrastructural features of both astrocytes and OC and the finding of GFAP within the immature OC strongly support the hypothesis that OC in the developing central nervous system may arise from astroglial precursors. These observations also suggest that the MSC may be a suitable model for the study of OC differentiation and myelinogenesis in man.