Project description:Somatic mutations in genes implicated in DNA methylation (DNAme; e.g., TET2, DNMT3A and IDH2), are frequently observed in hematological malignancies, as well as in clonal hematopoiesis (CH). Yet, how these mutations disrupt the hematopoietic differentiation topology remains largely unknown. By applying complementary single-cell sequencing approaches to murine bone marrow hematopoietic stem and progenitor cells, we observe that mutations in DNAme modifiers result in significantly altered differentiation topology. In particular, we find shifts in the frequencies of erythroid vs. myelo-monocytic progenitors, which can be traced back to fate-priming skews in the earliest uncommitted hematopoietic stem cells (HSCs). DNAme analysis both in open chromatin regions and at single-cell resolution, demonstrate that methylation changes resulting from DNAme modifier disruption are distributed stochastically across the genome. To reconcile the distributed nature of DNAme changes with the deterministic erythroid vs. myelo-monocytic topological skews, our data implicate differential sensitivity of key transcription factors to global methylation changes due to biases in CpG enrichment in their binding motifs. Finally, by coupling single-cell whole transcriptome analysis with targeted genotyping, we observe a similar skew in early transcriptional priming impact human CH bone marrow progenitors in an individual with DNMT3A-755S mutation. Thus, our results provide evidence that DNAme encodes topological information for hematopoietic differentiation.
Project description:Cell fate decisions during hematopoiesis are governed by lineage-specific transcription factors, such as RUNX1, SCL/TAL1, FLI1 and C/EBP family members. In order to gain insight about how these transcription factors regulate the activation of hematopoietic genes during embryonic development, we measured the genome-wide dynamics of transcription factor assembly on their target genes during the RUNX1-dependent transition from hemogenic endothelium to hematopoietic progenitors. Using a RUNX1-/- embryonic stem cell differentiation model expressing an inducible RUNX1 gene, we show that in the absence of RUNX1, SCL/TAL1, FLI1 and C/EBP-beta prime hematopoietic genes and that this early priming is required for correct temporal expression of the myeloid master regulator PU.1 and its downstream targets. After induction, RUNX1 binds to numerous new sites, initiating a local increase of histone acetylation and rapid global alterations in the binding patterns of SCL/TAL1 and FLI1. The acquisition of hematopoietic fate controlled by RUNX1 therefore does not represent the establishment of a new regulatory layer on top of a pre-existing hemogenic endothelium program but instead entails global reorganization of lineage-specific transcription factor assemblies. Microarray expression data obtained from differentiating murine hematopoietic cells, 3 independent biological replicates (measured twice) from iRUNX1 culture -/+DOX induction
Project description:Cell fate decisions during hematopoiesis are governed by lineage-specific transcription factors, such as RUNX1, SCL/TAL1, FLI1 and C/EBP family members. In order to gain insight about how these transcription factors regulate the activation of hematopoietic genes during embryonic development, we measured the genome-wide dynamics of transcription factor assembly on their target genes during the RUNX1-dependent transition from hemogenic endothelium to hematopoietic progenitors. Using a RUNX1-/- embryonic stem cell differentiation model expressing an inducible RUNX1 gene, we show that in the absence of RUNX1, SCL/TAL1, FLI1 and C/EBPM-NM-2 prime hematopoietic genes and that this early priming is required for correct temporal expression of the myeloid master regulator PU.1 and its downstream targets. After induction, RUNX1 binds to numerous new sites, initiating a local increase of histone acetylation and rapid global alterations in the binding patterns of SCL/TAL1 and FLI1. The acquisition of hematopoietic fate controlled by RUNX1 therefore does not represent the establishment of a new regulatory layer on top of a pre-existing hemogenic endothelium program but instead entails global reorganization of lineage-specific transcription factor assemblies. ChIPseq data from transcription factors Runx1, Fli-1, Scl/Tal1 and C/EBPM-NM-2, histone modification H3K9Ac as well as RNA Pol II obtained from differentiating murine hematopoietic cells
Project description:Global mechanisms defining the gene expression programs specific for hematopoiesis are still not fully understood. Here, we show that promoter DNA demethylation is associated the activation of hematopoietic-specific genes. Using genome-wide promoter methylation arrays, we identified 694 hematopoietic-specific genes repressed by promoter DNA methylation in human ESCs and whose loss of methylation in hematopoietic can be associated with gene expression. The association between promoter methylation and gene expression was studied for many hematopoietic-specific genes including CD45, CD34, CD28, CD19, the T cell receptor (TCR), the MHC class II gene HLA-DR, perforin 1, and the phosphoinositide 3-kinase (PI3K) and results indicated that DNA demethylation was not always sufficient for gene activation. Promoter demethylation occurred either early during embryonic development or later on during hematopoietic differentiation. Analysis of the genome-wide promoter methylation status of induced pluripotent stem cells (iPSCs) generated from somatic CD34+ HSPCs and differentiated derivatives from CD34+ HSPCs confirmed the role of DNA methylation in regulating the expression of genes of the hemato-immune system, and indicated that promoter methylation of these genes may be associated to stemness. Together, these data suggest that promoter DNA demethylation might play a role in the tissue/cell-specific genome-wide gene regulation within the hematopoietic compartment. Total DNA isolated by standard procedures from different primary samples corresponding to healthy patients and several cell lines.