Project description:Blood develops in distinct stages. Haematopoietic progenitors in the embryo manifest restricted differentiation potential relative to definitive haematopoietic stem cells in adult bone marrow, which support lifelong multilineage haematopoiesis. To identify regulators of embryonic haematopoiesis, we screened chromatin modifiers and identified the Polycomb group protein EZH1 as a barrier to multilineage potential from pluripotent stem cells (PSCs). EZH1 was directly bound to bivalently poised, yet restricted, HSC and lymphoid genes in primitive progenitors; knockdown enabled robust generation of multilineage progenitors. Moreover, EZH1 haploinsufficiency promoted the generation of HSCs with long-term, multilineage and self-renewal potential from sites of embryonic haematopoiesis in vivo. Together, this work identifies EZH1 as a key epigenetic barrier to definitive haematopoiesis during embryonic development, and highlights the utility of chromatin modifiers as cell engineering targets to enhance blood differentiation from PSCs.
Project description:Blood develops in distinct stages. Haematopoietic progenitors in the embryo manifest restricted differentiation potential relative to definitive haematopoietic stem cells in adult bone marrow, which support lifelong multilineage haematopoiesis. To identify regulators of embryonic haematopoiesis, we screened chromatin modifiers and identified the Polycomb group protein EZH1 as a barrier to multilineage potential from pluripotent stem cells (PSCs). EZH1 was directly bound to bivalently poised, yet restricted, HSC and lymphoid genes in primitive progenitors; knockdown enabled robust generation of multilineage progenitors. Moreover, EZH1 haploinsufficiency promoted the generation of HSCs with long-term, multilineage and self-renewal potential from sites of embryonic haematopoiesis in vivo. Together, this work identifies EZH1 as a key epigenetic barrier to definitive haematopoiesis during embryonic development, and highlights the utility of chromatin modifiers as cell engineering targets to enhance blood differentiation from PSCs.
Project description:Blood develops in distinct stages. Haematopoietic progenitors in the embryo manifest restricted differentiation potential relative to definitive haematopoietic stem cells in adult bone marrow, which support lifelong multilineage haematopoiesis. To identify regulators of embryonic haematopoiesis, we screened chromatin modifiers and identified the Polycomb group protein EZH1 as a barrier to multilineage potential from pluripotent stem cells (PSCs). EZH1 was directly bound to bivalently poised, yet restricted, HSC and lymphoid genes in primitive progenitors; knockdown enabled robust generation of multilineage progenitors. Moreover, EZH1 haploinsufficiency promoted the generation of HSCs with long-term, multilineage and self-renewal potential from sites of embryonic haematopoiesis in vivo. Together, this work identifies EZH1 as a key epigenetic barrier to definitive haematopoiesis during embryonic development, and highlights the utility of chromatin modifiers as cell engineering targets to enhance blood differentiation from PSCs.
Project description:Polycomb group (PcG) proteins initiate the formation of repressed chromatin domains and regulate developmental gene expression. A mammalian PcG protein, Enhancer of Zeste homolog 2 (Ezh2), triggers transcriptional repression by catalyzing the addition of methyl groups onto lysine-27 of histone H3 (H3K27me2/3)1. This action facilitates the binding of other PcG proteins to histone H3 and compaction of chromatin. Interestingly, there exists a paralog of Ezh2, termed Ezh1, whose primary function remains unclear. Here, we provide evidence for genome-wide association of Ezh1 with active epigenetic marks, RNA polymerase II (PolII) and mRNA production. Ezh1 depletion reduced global PolII occupancy within gene bodies and resulted in delayed transcriptional activation during differentiation of skeletal muscle cells. Conversely, ectopic expression of wild-type Ezh1 led to premature gene activation and rescued PolII-elongation defects in Ezh1-depleted cells. Collectively, these findings reveal an unanticipated role of a PcG protein in promoting mRNA transcription. Examination of 3 different histone modifications, 3 modified forms of RNA polymerase II, Ezh1, Ezh2 and mRNA levels in a skeletal muscle cells at various developmental stages.
Project description:We previously reported the requirement of Polycomb Repressive Complex 2 (PRC2) for spermatogenesis through transcriptional repression of somatic genes and meiosis-specific genes. To characterize how PRC2's two methyltransferase subunits, EZH1 and EZH2, regulate histone H3 lysine 27 (H3K27) methylation during germ cell development, we generated mouse models with a germline ablation of EZH1 and/or EHZ2. Only the combined loss of EZH1 and EZH2 caused a depletion of global H3K27me3 marks and meiotic arrest in spermatocytes. Genome-wide analysis of H3K27me3 in spermatogenic cells revealed that a noncanonical EZH1-PRC2 could establish and maintain this histone mark on somatic genes and certain meiotic genes. Consistent with it having active enhancers in testis, Ezh1 was not only abundant in highly differentiated spermatocytes but also in actively proliferating progenitor and stem germ cells. Taken together, our findings suggest that the expression level of Ezh1 determines the restoration of H3K27 methylation in the absence of the canonical EZH2-PRC2.
Project description:A mouse AGM-derived cell line, AGM-s3, was shown to support the development of hematopoietic stem cells. To elucidate the molecular mechanisms regulating early hematopoiesis, we obtained subclones from AGM-s3, some of which were hematopoiesis supportive (s3-A9) and others which were non-supportive (s3-A7), and we analyzed the gene expression profiles by gene chip analysis. Experiment Overall Design: Genome-wide gene expression was examined using Affymetrix GeneChip array. Assays were performed according to the manufacturer's protocol. Total RNA was isolated from each stromal cell lines. We analysed 3 cell lines, AGM-s3-A9, AGM-s3-A7 and OP9. AGM-s3-A9 and OP9 are hematopoiesis supportive cell lines. AGM-s3-A7 is a hematopoiesis non-supportive cell line.
Project description:Trimethylation on H3K27 (H3K27me3) mediated by Polycomb repressive complex 2 (PRC2) has been linked to embryonic stem cell (ESC) identity and pluripotency. EZH2, the catalytic subunit of PRC2, has been reported as the sole histone methyltransferase that methylates H3K27 and mediates transcriptional silencing. Analysis of Ezh2(-/-) ESCs suggests existence of an additional enzyme(s) catalyzing H3K27 methylation. We have identified EZH1, a homolog of EZH2 that is physically present in a noncanonical PRC2 complex, as an H3K27 methyltransferase in vivo and in vitro. EZH1 colocalizes with the H3K27me3 mark on chromatin and preferentially preserves this mark on development-related genes in Ezh2(-/-) ESCs. Depletion of Ezh1 in cells lacking Ezh2 abolishes residual methylation on H3K27 and derepresses H3K27me3 target genes, demonstrating a role of EZH1 in safeguarding ESC identity. Ezh1 partially complements Ezh2 in executing pluripotency during ESC differentiation, suggesting that cell-fate transitions require epigenetic specificity.
Project description:In the present study, we found that EZH1 depletion in MYCN-amplified neuroblastoma cells resulted in significant cell death as well as xenograft inhibition. EZH1 depletion decreased the level of H3K27me1; the interaction and protein stabilization of MYCN and EZH1 appear to play roles in epigenetic transcriptional regulation. Transcriptome analysis of EZH1-depleted cells resulted in down-regulation of the cell cycle progression-related pathway. In particular, GSEA revealed down-regulation of reactome E2F-mediated regulation of DNA replication along with key genes of this process, TYMS, POLA2, and CCNA1. TYMS and POLA2 were transcriptionally activated by MYCN and EZH1-related epigenetic modification. Treatment with the EZH1/2 inhibitor UNC1999 also induced cell death, decreased H3K27 methylation, and reduced the levels of TYMS in NB cells. Previous reports indicated neuroblastoma cells are resistant to 5-fluorouracil (5-FU) and TYMS (encoding thymidylate synthetase) has been considered the primary site of action for folate analogues. Intriguingly, UNC1999 treatment significantly sensitized MYCN-amplified neuroblastoma cells to 5-FU treatment, suggesting that EZH inhibition may be an effective strategy for development of a new epigenetic treatment for neuroblastoma.
Project description:Polycomb group (PcG) proteins initiate the formation of repressed chromatin domains and regulate developmental gene expression. A mammalian PcG protein, Enhancer of Zeste homolog 2 (Ezh2), triggers transcriptional repression by catalyzing the addition of methyl groups onto lysine-27 of histone H3 (H3K27me2/3)1. This action facilitates the binding of other PcG proteins to histone H3 and compaction of chromatin. Interestingly, there exists a paralog of Ezh2, termed Ezh1, whose primary function remains unclear. Here, we provide evidence for genome-wide association of Ezh1 with active epigenetic marks, RNA polymerase II (PolII) and mRNA production. Ezh1 depletion reduced global PolII occupancy within gene bodies and resulted in delayed transcriptional activation during differentiation of skeletal muscle cells. Conversely, ectopic expression of wild-type Ezh1 led to premature gene activation and rescued PolII-elongation defects in Ezh1-depleted cells. Collectively, these findings reveal an unanticipated role of a PcG protein in promoting mRNA transcription.