The state of histone marks was found to evolve with the development of NSCs. After four-days culture, the NSCs in the core of the differentiating neurosphere exhibited a mosaic pattern of 2me-H3K4-im (Figure 2 top panel) with weakly stained cells interspersed among groups of highly stained cells (as per intensity calibrations, Figure 2 bottom panel); many cells in the core retained OCT4 expression. NSCs beginning to differentiate at the periphery of the neurosphere showed significantly decreased 2me-H3K4 marks (p-value < 0.05), compared to the differentiated core. As their differentiation program advanced, they began to exhibit a significant increase (p-value < 0.05) in 2me-H3K4 marks as they migrated out from the neurosphere periphery (Figure 2 top panel). A few small groups of migrated neural progenitors in the distal areas had a further increase in 2me-H3K4-im (p-value < 0.05), compared to the periphery and proximal areas (Table 1, Figure 2 top panel, compare E, F, G; periphery, migrated proximal, migrated distal, respectively). Many of the migrated population of 2me-H3K4+ cells also expressed PCNA, indicating continued proliferation at the time of subplating. Double-staining
