siDNMT1 increases γ-globin expression in chemical inducer of dimerization (CID)-dependent mouse βYAC bone marrow cells and in baboon erythroid progenitor cell cultures.

OBJECTIVE: These studies were performed to test the hypothesis that DNMT1 is required for maintenance of DNA methylation and repression of the γ-globin gene in adult-stage erythroid cells.
MATERIALS AND METHODS: DNMT1 levels were reduced by nucleofection of small interfering RNA targeting DNMT1 in chemical inducer of dimerization-dependent multipotential mouse bone marrow cells containing the human β-globin gene locus in the context of a yeast artificial chromosome and in primary cultures of erythroid progenitor cells derived from CD34(+) baboon bone marrow cells. The effect of reduced DNMT1 levels on globin gene expression was measured by real-time polymerase chain reaction and the effect on globin chain synthesis in primary erythroid progenitor cell cultures was determined by biosynthetic radiolabeling of globin chains followed by high-performance liquid chromatography analysis. The effect on DNA methylation was determined by bisulfite sequence analysis.
RESULTS: Reduced DNMT1 levels in cells treated with siDNMT1 were associated with increased expression of γ-globin messenger RNA, an increased γ/γ+β chain ratio in cultured erythroid progenitors, and decreased DNA methylation of the γ-globin promoter. Similar effects were observed in cells treated with decitabine, a pharmacological inhibitor of DNA methyltransferase inhibitor.
CONCLUSIONS: DNMT1 is required to maintain DNA methylation of the γ-globin gene promoter and repress γ-globin gene expression in adult-stage erythroid cells.