NKX2-2 and myeloid sarcoma: Double immunofluorescent labeling of CXCR7 in combination with Nogo-A (see arrows in Fig 1H–1H'') and Nkx2.2, a transcription factor strongly expressed in the nucleus of OPCs (see arrow in Fig 1I–1I''; [5]) then confirmed that both mature and precursor cells in remyelinating MS lesions express CXCR7.