Confluence-Induced Squamous Differentiation Is Not Accompanied by Changes in H3K27me3 Repressive Epigenetic Mark

Recent studies have reported that epigenetic mechanisms may regulate the initiation and progress of squamous differentiation in normal and transformed keratinocytes. In particular, the role of the repressive H3K27me3 mark in the regulation of squamous differentiation has been prominent. However, there is conflicting literature showing that squamous differentiation may be dependent upon or independent of changes in H3K27me3 status. In this study we have examined the binding of trimethylated H3K27 to the promoters of proliferation or differentiation genes in keratinocytes undergoing squamous differentiation in vitro and in vivo. Initially, we examined the expression levels for EZH1, EZH2, and H3K27me3 in differentiating keratinocytes in vitro and in vivo. We extended this to include H3K27me3 chromatin immunoprecipitation sequencing (ChIP-seq). Based on these studies, we could find no evidence for an association between widespread gain or loss of H3K27me3 on the promoters of proliferation-specific or differentiation-specific target genes, respectively, during squamous differentiation in adult human keratinocytes. These data suggest that squamous differentiation may occur independent of regulation by H3K27me3 on proliferation and differentiation genes of normal adult human keratinocytes.