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High resolution methylome analysis reveals widespread functional hypomethylation during adult human erythropoiesis

ABSTRACT: Differentiation of hematopoietic stem cells to red cells requires coordinated expression of numerous erythroid genes. To understand the regulatory mechanisms governing lineage commitment we conducted a high resolution methylomic and transcriptomic analysis of six major stages of human erythroid differentiation. We observed widespread epigenetic differences between early and late stages of erythropoiesis with progressive loss of methylation being the dominant change during differentiation. Gene bodies, intergenic regions and CpG shores were preferentially demethylated during erythropoiesis. Epigenetic changes at transcription factor binding sites correlated significantly with changes in gene expression and were enriched for binding motifs for SCL, MYB, GATA and other factors not previously implicated in erythropoiesis. Demethylation at gene promoters was associated with increased expression of genes, while epigenetic changes at gene bodies correlated inversely with gene expression. Important gene networks encoding erythrocyte membrane proteins, surface receptors and heme synthesis proteins were found to be regulated by DNA methylation. Furthermore, integrative analysis enabled us to identify novel, potential regulatory areas of the genome that underwent differential methylation and correlated with corresponding changes in gene expression, as evident by epigenetic changes in a predicted PU.1 binding site in intron 1 of the GATA1 gene. This intronic site was found to be conserved across species and was validated to be a novel PU.1 binding site by qCHIP in erythroid cells. Altogether, our study provides a comprehensive analysis of methylomic and transcriptomic changes during erythroid differentiation and demonstrates that hypomethylation of the genome during erythroid differentiation has implications in modulating gene expression.

ORGANISM(S): Homo sapiens

PROVIDER: GSE44054 | GEO | 2013/02/05

SECONDARY ACCESSION(S): PRJNA188461

REPOSITORIES: GEO

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Project description:Differentiation of hematopoietic stem cells to red cells requires coordinated expression of numerous erythroid genes. To understand the regulatory mechanisms governing lineage commitment we conducted a high resolution methylomic and transcriptomic analysis of six major stages of human erythroid differentiation. We observed widespread epigenetic differences between early and late stages of erythropoiesis with progressive loss of methylation being the dominant change during differentiation. Gene bodies, intergenic regions and CpG shores were preferentially demethylated during erythropoiesis. Epigenetic changes at transcription factor binding sites correlated significantly with changes in gene expression and were enriched for binding motifs for SCL, MYB, GATA and other factors not previously implicated in erythropoiesis. Demethylation at gene promoters was associated with increased expression of genes, while epigenetic changes at gene bodies correlated inversely with gene expression. Important gene networks encoding erythrocyte membrane proteins, surface receptors and heme synthesis proteins were found to be regulated by DNA methylation. Furthermore, integrative analysis enabled us to identify novel, potential regulatory areas of the genome that underwent differential methylation and correlated with corresponding changes in gene expression, as evident by epigenetic changes in a predicted PU.1 binding site in intron 1 of the GATA1 gene. This intronic site was found to be conserved across species and was validated to be a novel PU.1 binding site by qCHIP in erythroid cells. Altogether, our study provides a comprehensive analysis of methylomic and transcriptomic changes during erythroid differentiation and demonstrates that hypomethylation of the genome during erythroid differentiation has implications in modulating gene expression. We examined changes in methylation on days 0, 3, 7, 10, 13 and 16 of human erythroid culture. Two independent sets of experiments were performed.

Project description:It is unclear how epigenetic changes regulate the induction of erythroid-specific genes during terminal erythropoiesis. Here we use global mRNA sequencing (mRNA-seq) and chromatin immunoprecipitation coupled to high-throughput sequencing (CHIP-seq) to investigate the changes that occur in mRNA levels, RNA Polymerase II (Pol II) occupancy and multiple post-translational histone modifications when erythroid progenitors differentiate into late erythroblasts. Among genes induced during this developmental transition, there was an increase in the occupancy of Pol II, the activation marks H3K4me2, H3K4me3, H3K9Ac and H4K16Ac, and the elongation methylation mark H3K79me2. In contrast, genes that were repressed during differentiation showed relative decreases in H3K79me2 levels yet had levels of Pol II binding and active histone marks similar to those in erythroid progenitors. We also found that relative changes in histone modification levels-in particular, H3K79me2 and H4K16ac-were most predictive of gene expression patterns. Our results suggest that in terminal erythropoiesis both promoter and elongation-associated marks contribute to the induction of erythroid genes, while gene repression is marked by changes in histone modifications mediating Pol II elongation. Our data maps the epigenetic landscape of terminal erythropoiesis and suggests that control of transcription elongation regulates gene expression during terminal erythroid differentiation. Mouse fetal liver cells are double-labeled for erythroid-specific TER119 and non erythroid-specific transferrin receptor (CD71) and then sorted by flow-cytometry. E14.5 fetal livers contain at least five distinct populations of cells (R1 through R5); as they progressively differentiate they gain TER119 and then gain and subsequently lose CD71. CFU-E cells and proerythroblasts make up the R1 population; R2 consists of proerythroblasts and early basophilic erythroblasts; R3 includes early and late basophilic erythroblasts; R4 is mostly polychromatophilic and orthochromatophilic erythroblasts; and R5 is comprised of late orthochromatophilic erythroblasts and reticulocytes. We have sorted for R2-R5 cells for RNA-seq experiment.

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High resolution methylome analysis reveals widespread functional hypomethylation during adult human erythropoiesis

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