Human α, β, and exocrine cells exhibit convergent monovalent H3K4me3 and H3K27me3 profiles, which correlate highly with genome-wide expression data.
(A) The majority of H3K4me3-marked genes are shared between α, β, and exocrine cells (their overlap is indicated in the purple portion of the bars, 83%–95%). (B) H3K27me3 modification patterns are similar among pancreatic cell types (73%–83%, dark blue portion of the bars). (C and D) Heat map analysis (columns, individual samples; rows, genes) confirms low interindividual variability for all H3K4me3 (C) and H3K27me3 (D) peaks identified from the pooled data (peaks called by algorithms are indicated by the solid bars on the left of the heat maps). All pairs of columns in every heat map are significantly correlated based on correlation t test assessed by R statistics software (P < 2.2 × 10–16). (E–G) Normalized expression values obtained by RNA-Seq for genes grouped by their histone modification status in each cell type are shifted significantly above or below baseline expression (Wilcoxon signed rank test, P < 2.2 × 10–16). A shift above 0 on this scale indicates highly expressed genes and was observed for gene groups marked solely by H3K4me3 in all cell types (pink boxes in E–G). A shift below 0 on this scale indicates low or nonexpressed genes and was observed in all bivalently marked gene groups (light blue boxes) and monovalently H3K27me3-marked genes (dark blue boxes) in all cell types. Therefore, the histone modification states are significantly correlated with gene expression levels.