For imaging, all pictures were taken using a Leitz Orthoplan2 microscope interfaced with a Spot RT color camera. Fluorescent images were viewed using the appropriate filter and most images were taken using exposure with consistent gamma and contrast in each antibody staining. Intensity observations for qualitative data were determined independently by consensus of two analyzers based on the following criteria. To verify the intra-cellular and intra-nuclear distribution of the epigenetic marks, we have examined the cells under both fluorescent- and phase-contrast bright-field microscopy, alternatively or simultaneously (with dimmed bright-field). The outline of the cell versus nuclear membrane is clearly distinguishable under Leitz microscope. Semi-quantitative measurement of observed intensity levels was done using Image J (National Institutes of Health, Bethesda, MD). Fluorescent images of twelve neurospheres or migrated regions were captured at 25 or 40x magnification. Determination of positive staining was based on the camera's capture of a discernable image above background (black) level and by overlay of DAPI staining and/or bright field images from the analogous field. Alexa 488 stained fluorescent images were converted to 8-bit color format and analyzed
