Epigenetic inactivation of ERF reactivates γ-globin expression in β-thalassemia

摘要

The fetal-to-adult hemoglobin switch is regulated in a developmental stage-specific manner and reactivation of fetal hemoglobin (HbF) has therapeutic implications for treatment of beta-thalassemia and sickle cell anemia, two major global health problems. Although significant progress has been made in our understanding of the molecular mechanism of the fetal-to-adult hemoglobin switch, the mechanism of epigenetic regulation of HbF silencing remains to be fully defined. Here, we performed whole-genome bisulfite sequencing and RNA sequencing analysis of the bone marrow-derived GYPAthorn erythroid cells from beta-thalassemia-affected individuals with widely varying levels of HbF groups (HbF >= 95th percentile or HbF <= 5th percentile) to screen epigenetic modulators of HbF and phenotypic diversity of beta-thalassemia. We identified an ETS2 repressor factor encoded by ERF, whose promoter hypermethylation and mRNA down-regulation are associated with high HbF levels in beta-thalassemia. We further observed that hypermethylation of the ERF promoter mediated by enrichment of DNMT3A leads to demethylation of gamma-globin genes and attenuation of binding of ERF on the HBG promoter and eventually re-activation of HbF in beta-thalassemia. We demonstrated that ERF depletion markedly increased HbF production in human CD34(+) erythroid progenitor cells, HUDEP-2 cell lines, and transplanted NCG-Kit-V831M mice. ERF represses gamma-globin expression by directly binding to two consensus motifs regulating gamma-globin gene expression. Importantly, ERF depletion did not affect maturation of erythroid cells. Identification of alterations in DNA methylation of ERF as a modulator of HbF synthesis opens up therapeutic targets for beta-hemoglobinopathies.

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