NG2-expressing cells in the nervous system revealed by the NG2-EYFP-knockin mouse.

The NG2 glycoprotein is a type I membrane protein expressed by immature cells in the developing and adult mouse. NG2+ cells of the embryonic and adult brain have been principally viewed as oligodendrocyte precursor cells but have additionally been considered a fourth glial class. They are likely to be a heterogeneous population. In order to facilitate studies on the function of NG2+ cells and to characterize these cells in situ, we generated an enhanced yellow fluorescent protein (EYFP) "knockin mouse." EYFP-expressing cells in heterozygous knockin mice expressed the NG2 protein in all regions and at all ages studied. The EYFP+ cells did not express markers of mature glia, developing or mature neurons or microglia, but expressed markers typical for immature oligodendrocyte-lineage cells. Examination of the hippocampus showed heterogeneity in the population with regard to expression of S100ss and glutamine synthetase. Furthermore, different subpopulations of NG2+ cells in the hippocampus could be recognized by their electrophysiological properties.