Genome-wide mapping of bivalent histone modifications in hepatic stem/progenitor cells

Bivalent domain is characterized by repressive trimethylation of histone H3 at lysine 27 (H3K27me3) marks and active trimethylation of histone H3 at lysine 4 (H3K4me3) marks. Although maintenance and dynamic resolution of these histone marks play an important role in regulation of differentiation process in a variety of stem cell systems, little is known in hepatic stem/progenitor cells. In the present study, we conducted chromatin immunoprecipitation (ChIP) followed by high- throughput DNA sequencing (ChIP-seq) analyses in purified delta-like 1 protein (Dlk)+ hepatic stem/progenitor cells and successfully identified 562 bivalent genes showing bivalent domain in the region within 2 kb of the transcriptional start sites. Gene Ontology analysis revealed that these genes were enriched in developmental function and differentiation process.