Correlation between gene expression and changes in histone modifications during erythroid differentiation. (A) Clustergram showing the fold change in enrichment of histone marks (columns) for induced and repressed genes (rows) compared with the fold change in expression for the same genes. Both types of ratios are expressed as log2 ratios (late erythroblasts relative to enriched CFU-Es). Genes that are black in the expression column (unchanged ratios) are constitutively expressed genes with RPKM > 2 and < 0.2 fold change between the R2 and R3 stages. (B) Cumulative distribution function plots comparing mRNA expression ratios (late erythroblasts relative to enriched CFU-Es) for the set of all genes with significant enrichment in a specific histone mark (red line) or decrease in that mark (blue line), against the set of all genes (black line). Shifts to the right signify a positive correlation; shifts to the left a negative correlation. K-S test P values are shown on each graph; values < .001 for a line signify that the subset of genes is highly significantly different from the black line. Histone marks are indicated above each graph.
