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Integrative analysis of 3D nucleome and chromatin accessibility reveals a chromatin barrier established for T-lineage commitment during early T cell development [ChIP-Seq]

ABSTRACT: Hematopoiesis consists of step-wise commitment of multiple distinct intermediate differentiation stages before mature blood cells are generated1,2. Early progenitor cells have multiple cell fate potentials and retain plasticity to differentiate to alternative lineages, while later stages are fully committed to certain cell lineages and rarely alter their fates3,4. Although extensive studies have been performed on regulatory pathways in mature blood cells5-8, few have examined chromatin re-organization underlying the transcription programs in early progenitors of hematopoiesis. In particular, what roles chromatin organization plays in the cell fate commitment during the differentiation of early hematopoietic progenitor cells remains unclear. Here, we carried out an integrative analysis of 3D nucleome, chromatin accessibility and gene expression during early T cell development from hematopoietic stem cells (HSC) to CD4/CD8 double positive (DP) T cells. Analysis of these data sets revealed extensive A/B compartment flips and dynamic changes of chromatin accessibility at regulatory regions including promoters and enhancers during the development process. Remarkably, both the compartment flip and changes in chromatin accessibility display a monotonic pattern. While gradual and progressive changes in chromatin re-organization was observed at most development stages, an abrupt and striking genome-wide change in A/B compartment structure and chromatin accessibility occurred during the transition from double negative stage 2 (DN2) to DN3, which was accompanied with the loss of cell fate plasticity of DN3 to differentiate to alternative lineages, suggesting that a chromatin barrier is established at the DN3 stage to lock the cells in the T cell fate. The binding of PU.1, a key factor for the fate choice of early progenitor cells, and BCL11B, critically required for T cell commitment at late stages, was associated with increased long-distance interaction and chromatin accessibility and may coordinately contribute to the establishment of the 3D nucleome structure required for the lineage differentiation and commitment.

ORGANISM(S): Mus musculus

PROVIDER: GSE79874 | GEO | 2018/02/20

REPOSITORIES: GEO

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Project description:Hematopoiesis consists of step-wise commitment of multiple distinct intermediate differentiation stages before mature blood cells are generated. Although extensive studies have been performed on regulatory pathways in mature blood cells, few have examined chromatin reorganization underlying the changes in transcription programs from early progenitors of hematopoiesis to mature immune cells. In particular, what roles chromatin organization plays in the cell fate commitment during the differentiation of early hematopoietic progenitor cells to committed T cells remains unclear. Here, we carried out an integrative analysis of 3D nucleome, chromatin accessibility and gene expression from hematopoietic stem cells (HSC) to CD4/CD8 double positive (DP) T cells. Analysis of these data sets revealed extensive reorganization of A/B compartments, topologically associating domains (TADs), and chromatin accessibility at transcriptional regulatory regions during the development process. Remarkably, all three levels of chromatin organization display a monotonic pattern of change. While gradual and progressive changes in chromatin reorganization was observed at most development stages, an abrupt genome-wide change in A/B compartment structure, TAD domain scores and chromatin accessibility occurred during the transition from double negative stage 2 (DN2) to DN3, which was accompanied with the loss of cell fate plasticity of DN3 to differentiate to alternative lineages, suggesting that a chromatin barrier is established at the DN3 stage to lock the cells in the T cell fate. This chromatin barrier may be reinforced by another genome-wide reorganization of chromatin at the DN4-to-DP transition. The binding of PU.1, a key factor for the fate choice of early progenitor cells, and BCL11B, critically required for T cell commitment at later stages, was associated with increased long-distance interaction and chromatin accessibility. Deletion of Bcl11b led to decreased chromatin interaction for BCL11B target genes, suggesting that it may contribute to the establishment of the 3D nucleome structure required for the lineage differentiation and commitment.

Project description:Epigenetic modifications must underlie lineage-specific differentiation since terminally differentiated cells express tissue-specific genes, but their DNA sequence is unchanged. Hematopoiesis provides a well-defined model of progressive differentiation in which to study the role of epigenetic modifications in cell fate decisions. Multi-potent progenitors (MPPs) can differentiate into all blood cell lineages, while downstream progenitors commit to either myeloerythroid or lymphoid lineages. While DNA methylation is critical for myeloid versus lymphoid differentiation, as demonstrated by the myeloerythroid bias in Dnmt1 hypomorphs {Broske, 2009 #6}, a comprehensive DNA methylation map of hematopoietic progenitors, or of any cell lineage, does not exist. Here we have generated a mouse DNA methylation map, examining 4.6 million CpG sites throughout the genome including all CpG islands and shores, examining MPPs, all lymphoid progenitors (ALPs), common myeloid progenitors (CMPs), granulocyte/macrophage progenitors (GMPs), and thymocyte progenitors (DN1, DN2, DN3). Interestingly, differentiation towards the myeloid lineage corresponds with a net decrease in DNA methylation, while lymphoid commitment involves a net increase in DNA methylation, but both show substantial dynamic changes consistent with epigenetic plasticity during development. By comparing lineage-specific DNA methylation to gene expression array data, we find many examples of genes and pathways not previously known to be involved in lymphoid/myeloid differentiation, such as Gcnt2, Arl4c, Gadd45α, and Jdp2. Several transcription factors, including Meis1 and Prdm16 were methylated and silenced during differentiation, suggesting a role in maintaining an undifferentiated state. Additionally, epigenetic modification of modifiers of the epigenome appears to be important in hematopoietic differentiation. Our results directly demonstrate that modulation of DNA methylation occurs during lineage-specific differentiation, often correlating with gene expression changes, and define a comprehensive map of the methylation and transcriptional changes that accompany myeloid versus lymphoid fate decisions. mRNA expression of 8 hematopoietic progenitor populations [MPPFL-(5), MPPFL+(3), CMP(3), GMP(3), CLP(3), DN1(3), DN2(3), DN3(3)] were compared

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Integrative analysis of 3D nucleome and chromatin accessibility reveals a chromatin barrier established for T-lineage commitment during early T cell development [ChIP-Seq]

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