A glial progenitor cell that develops in vitro into an astrocyte or an oligodendrocyte depending on culture medium.

We have identified a cell type in 7-day-old rat optic nerve that differentiates into a fibrous astrocyte if cultured in the presence of fetal calf serum and into an oligodendrocyte if cultured in the absence of serum. In certain culture conditions some of these cells acquire a mixed phenotype, displaying properties of both astrocytes and oligodendrocytes. These observations suggest that fibrous astrocytes and oligodendrocytes develop from a common progenitor cell and provide a striking example of developmental plasticity and environmental influence in the differentiation of CNS glial cells.