Identification and characterization of early glial progenitors using a transgenic selection strategy

To define the spatiotemporal development of and simultaneously select for o ligodendrocytes (OLs) and Schwann cells (SCs), transgenic mice were generat ed that expressed a bacterial beta-galactosidase (beta-gal) and neomycin ph osphotransferase fusion protein (beta geo) under the control of murine 2'3' -cyclic nucleotide 3'-phosphodiesterase (muCNP) promoters I and II. Transge nic beta-gal activity was detected at embryonic day 12.5 in the ventral reg ion of the rhombencephalon and spinal cord and in the neural crest. When ce lls from the rhombencephalon were cultured in the presence of G418, survivi ng cells differentiated into OLs, indicating that during development this b rain region provides one source of OL progenitors. Postnatally, robust P-ga l activity was localized to OLs throughout the brain and was absent from as trocytes, neurons, and microglia or monocytes. In the sciatic nerve beta-ga l activity was localized exclusively to SCs. Cultures from postnatal day 10 brain or sciatic nerve were grown in the presence of G418, and within 8-9 d exposure to antibiotic, 99% of all surviving cells were beta-gal-positive OLs or SCs. These studies demonstrate that the muCNP-beta geo transgenic m ice are useful for identifying OLs and SCs beginning at early stages of the glial cell lineage and throughout their development. This novel approach d efinitively establishes that the beta-gal-positive cells identified in vivo are glial progenitors, as defined by their ability to survive antibiotic s election and differentiate into OLs or SCs in vitro. Moreover, this experim ental paradigm facilitates the rapid and efficient selection of pure popula tions of mouse OLs and SCs and further underscores the use of cell-specific promoters in the purification of distinct cell types.