The NG2 proteoglycan is a type I membrane protein that is expressed by a variety of immature cells of several embryonic tissue origins including glia, muscle progenitor cells, and pericytes (1). In the central nervous system, expression of NG2 was originally thought to specify oligodendroglial progenitor cells, but more recent data suggest that NG2-expressing cells encompass a wider range of immature glial cells in white and gray matter. These include glia that make synaptic-like contacts with neurons in the hippocampus and cerebellum (2) and glial cells specifically associated with the nodes of Ranvier (3). Interestingly, many NG2-positive cells are both proliferative and motile or exhibit local process motility (4, 5).