H3K4me3 profiles are consistent but H3K27me3-enriched regions change drastically during differentiation. (A) Heatmaps of H3K4me3 around TSSs sorted into 200 groups by HSPC expression show stable marking of the most highly expressed genes across all cell types and a depletion directly at the TSS. (B) Promoters consistently marked by H3K4me3 in the four hematopoietic cell types contain a CpG island more often than those that are inconsistently or not marked by H3K4me3. (C) RNA PolII heatmaps around TSSs sorted into 200 groups by HSPC expression show PolII binding at the most highly expressed genes directly at the TSS. (D) H3K27me3 heatmaps around TSSs sorted into 200 groups by HSPC expression show enrichment in the lowest expressed genes. (E) The distributions of the sizes of H3K27me3-enriched regions in ESC (black dotted), HSPC (grey), pRBC (red), T-cell (green), and B-cell (blue) show that H3K27me3-enriched regions grow in size in differentiated cell types in comparison with ESCs and HSPCs. (F) Percentages of the genome falling in SICER islands calculated for H3K27me3. (G) Most of the H3K27me3-enriched regions are cell type-specific. Regions of H3K27me3 enrichment were unified across all five cell types, broken evenly into ≤ 2kbp fragments, clustered by their H3K27me3 read counts, and displayed as a heatmap.