The adult human subcortical white matter harbors a population of mitotically-competent oligodendrocyte progenitors, that comprise as many as 3% of its cells (Scolding et al., “Oligodendrocyte Progenitors are Present in the Normal Adult Human CNS and in the Lesions of Multiple Sclerosis [see comments],” Brain, 121:2221-2228 (1998); Roy et al., “Identification, Isolation, and Promoter-Defined Separation of Mitotic Oligodendrocyte Progenitor Cells from the Adult Human Subcortical White Matter,” J Neurosci, 19:9986-9995 (1999)). These cells may be extracted from brain tissue using fluorescence-activated cell sorting (FACS), after transfection with plasmids encoding GFP driven by the promoter for CNP, an early oligodendrocytic transcript (Roy et al., “Identification, Isolation, and Promoter-Defined Separation of Mitotic Oligodendrocyte Progenitor Cells from the Adult Human Subcortical White Matter,” J Neurosci, 19:9986-9995 (1999); Gravel et al., “Four-Kilobase Sequence of the Mouse CNP Gene Directs Spatial and Temporal Expression of lacZ in Transgenic Mice,” J. Neurosci., Res. 53:393-404 (1998)). The cells express the immature neural ganglioside recognized by MAb A2B5, but do not express more mature markers of glial lineage. When raised at high density, P/CNP2:hGFP+ progenitors gave rise to glia, largely to oligodendrocytes. Nonetheless, in low density culture following high-purity FACS, P/CNP2:hGFP+ cells often generated βIII-tubulin+ neurons (Roy et al., “Identification, Isolation, and Promoter-Defined Separation of Mitotic Oligodendrocyte Progenitor Cells from the Adult Human Subcortical White Matter,” J Neurosci, 19:9986-9995 (1999)). Since neurogenesis was essentially never noted from P/CNP2:hGFP+ cells in higher-density or unsorted cultures, it was postulated that the restriction of P/CNP2:hGFP+ progenitor cells to oligodendrocytic phenotype might be an effect of environmental cues, rather than a function of autonomous commitment. As a result, once removed from other cells into high-purity, low-density culture, and hence absent other paracrine or autocrine influences, human subcortical P/CNP2:hGFP+ cells were able to generate neurons as well as glia. Subsequently, Kondo and Raff (Kondo et al., “Oligodendrocyte Precursor Cells Reprogrammed to Become Multipotential CNS Stem Cells,” Science, 289:1754-1757 (2000)) reported that glial progenitors from the postnatal rat optic nerve could be reprogrammed to generate neurons, following serum or bone morphogenetic protein-induced phenotypic instruction and bFGF-stimulated expansion. Taken together, these findings suggested that glial progenitor cells might retain substantial phenotypic plasticity.