Timing of myelin onset in white matter of ex vivo slice culture model. MBP expression at 1 DIV (A), 5 DIV (B), and 9 DIV (C) in white matter of organotypic slice cultures. There was a progressive increase in MBP expression in the white matter with time in culture. (D) At 9 DIV, robust expression of individual MBP positive cells was observed, which were co-localized with the oligodendrocyte nuclear transcription factor Olig2 (MBP: green, Olig2: red). (E) Evidence of onset of myelination in the white matter at 13 DIV. (F) Oligodendrocyte (arrow; DAPI: shown as pseudo-color in red) showing wrapping of axons stained with MBP (green; arrowhead). Scale: A-C, 500 μm; D, F, 20 μm; E, 250 μm.