The caveat is that olig2 expression in the adult normal brain of bacTRAP olig2 RP-eGFP mice labels both progenitors and mature oligodendrocytes, while recruited and tumor olig2 cells are almost entirely progenitors; therefore, some of the differences seen in the comparative analysis of normal, tumor and recruited olig2 cells may in part result from the shift in relative abundance of different progenitor and mature olig2 cell populations. This evidence concerns the gene OLIG2 and neoplasm.