OLIG2 and central nervous system cancer: Olig2 is expressed in myelinating oligodendroglia, but is also in mitogen-treated “transit-amplifying cells” of the SVZ, the presumed site of most neural progenitor cells and a theorized site for the origin of gliomas.105 Olig2 and Olig1 are basic-helix-loop-helix transcription factors expressed in neural and oligodendrocyte precursors.