Project description:Bone marrow mesenchymal stromal cells (MSCs) that express high levels of stem cell factor (SCF) and CXC chemokine ligand 12 (CXCL12) are one crucial component of the hematopoietic stem cell (HSC) niche. While the secreted factors produced by MSCs to support HSCs have been well described, little is known regarding the transcriptional regulators controlling the cell fate of MSCs and thus indirectly maintaining HSCs. Bmi1 is a polycomb group protein that regulates HSCs both cell intrinsically and extrinsically, but it is unknown in which cell type and how Bmi1 functions to maintain HSCs extrinsically. Here we show that Bmi1 maintains HSCs by preventing adipogenic differentiation of MSCs. Bmi1 is highly expressed in MSCs but becomes downregulated upon adipogenic differentiation and during aging. Deleting Bmi1 from MSCs increased marrow adipocytes, induced HSC quiescence and depletion, and impaired hematopoiesis. We found that Bmi1 repressed multiple developmental programs in MSCs by safeguarding the repressive epigenetic marks histone H2A ubiquitylation and H3 lysine 27 trimethylation. We identified a novel adipogenic program governed by Pax3, which Bmi1 repressed in MSCs. Our results establish Bmi1 as a critical regulator of MSC cell fate that suppresses marrow adipogenesis to create a supportive niche for HSCs.
Project description:Bone marrow mesenchymal stromal cells (MSCs) that express high levels of stem cell factor (SCF) and CXC chemokine ligand 12 (CXCL12) are one crucial component of the hematopoietic stem cell (HSC) niche. While the secreted factors produced by MSCs to support HSCs have been well described, little is known regarding the transcriptional regulators controlling the cell fate of MSCs and thus indirectly maintaining HSCs. Bmi1 is a polycomb group protein that regulates HSCs both cell intrinsically and extrinsically, but it is unknown in which cell type and how Bmi1 functions to maintain HSCs extrinsically. Here we show that Bmi1 maintains HSCs by preventing adipogenic differentiation of MSCs. Bmi1 is highly expressed in MSCs but becomes downregulated upon adipogenic differentiation and during aging. Deleting Bmi1 from MSCs increased marrow adipocytes, induced HSC quiescence and depletion, and impaired hematopoiesis. We found that Bmi1 repressed multiple developmental programs in MSCs by safeguarding the repressive epigenetic marks histone H2A ubiquitylation and H3 lysine 27 trimethylation. We identified a novel adipogenic program governed by Pax3, which Bmi1 repressed in MSCs. Our results establish Bmi1 as a critical regulator of MSC cell fate that suppresses marrow adipogenesis to create a supportive niche for HSCs.
Project description:Bmi1 is a component of the Polycomb-repressive complexes (PRC) and essential for maintaining the pool of adult stem cells. PRC are key regulators for embryonic development by modifying chromatin architecture and maintaining gene repression. To assess the role of Bmi1 in pluripotent stem cells and upon exit from pluripotency during differentiation, we studied forced Bmi1 expression in mouse embryonic stem cells (ESC). We found that ESC do not express detectable levels of Bmi1 RNA and protein and that forced Bmi1 expression had no obvious influence on ESC self-renewal. However, upon ESC differentiation Bmi1 effectively enhanced development of hematopoietic cells. Global transcriptional profiling identified a large array of genes that were differentially regulated during ESC differentiation by Bmi1. Importantly, we found that Bmi1 induced a prominent up-regulation of Gata2, a zinc finger transcription factor, which is essential for primitive hematopoietic cell generation from mesoderm. In addition, Bmi1 caused sustained growth and a more than 100-fold expansion of ESC-derived hematopoietic stem/progenitor cells within 2-3 weeks of culture. The enhanced proliferative capacity was associated with reduced Ink4a/Arf expression in Bmi1-transduced cells. Taken together, our experiments demonstrate distinct activities of Bmi1 in ESC and ESC-derived hematopoietic progenitor cells. In addition, Bmi1 enhances the propensity of ESC in differentiating towards the hematopoietic lineage. Thus, Bmi1 could be a candidate gene for engineered adult stem cell derivation from ESC. 8 samples in total. Bmi1 embryonic stem cells sample_1 (Bmi1_ESC_1) Bmi1 embryonic stem cells sample_2 (Bmi1_ESC_2) Untreated CCE embryonic stem cells (CCE_ESC_Control) Empty vector CCE embryonic stem cells (CCE_ESC_Vector) Bmi1 embryoid body sample_1 (Bmi1_EB_1) Bmi1 embryoid body sample_2 (Bmi1_EB_2) Empty vector control embryoid body sample_1 (Vector_EB_1) Empty vector control embryoid body sample_2 (Vector_EB_2)
Project description:Bmi1 is a component of the Polycomb-repressive complexes (PRC) and essential for maintaining the pool of adult stem cells. PRC are key regulators for embryonic development by modifying chromatin architecture and maintaining gene repression. To assess the role of Bmi1 in pluripotent stem cells and upon exit from pluripotency during differentiation, we studied forced Bmi1 expression in mouse embryonic stem cells (ESC). We found that ESC do not express detectable levels of Bmi1 RNA and protein and that forced Bmi1 expression had no obvious influence on ESC self-renewal. However, upon ESC differentiation Bmi1 effectively enhanced development of hematopoietic cells. Global transcriptional profiling identified a large array of genes that were differentially regulated during ESC differentiation by Bmi1. Importantly, we found that Bmi1 induced a prominent up-regulation of Gata2, a zinc finger transcription factor, which is essential for primitive hematopoietic cell generation from mesoderm. In addition, Bmi1 caused sustained growth and a more than 100-fold expansion of ESC-derived hematopoietic stem/progenitor cells within 2-3 weeks of culture. The enhanced proliferative capacity was associated with reduced Ink4a/Arf expression in Bmi1-transduced cells. Taken together, our experiments demonstrate distinct activities of Bmi1 in ESC and ESC-derived hematopoietic progenitor cells. In addition, Bmi1 enhances the propensity of ESC in differentiating towards the hematopoietic lineage. Thus, Bmi1 could be a candidate gene for engineered adult stem cell derivation from ESC.
Project description:Identification of BMI1, RYBP and H2AK119UB interactome in Glioblastoma (GBM) to elucidate BMI1 roles independent of the PRC1-complex in GBM.
Project description:Specialized niche environments specify and maintain stem and progenitor cells, but little is known about the identities and functional interactions of niche components in vivo. Here, we describe a modular system for the generation of artificial hematopoietic niches in the mouse embryo. A circumscribed tissue that lacks niche function but is physiologically accessible for hematopoietic progenitor cells is functionalized by individual and combinatorial expression of four factors, the chemokines Ccl25 and Cxcl12, the cytokine Scf and the Notch ligand DLL4. The distinct phenotypes and variable numbers of hematopoietic cells in the resulting niches reveal synergistic, context-dependent and hierarchical interactions among niche effector molecules. The surprisingly simple rules determining niche outcomes enable the in vivo engineering of artificial niches conducive to the presence of distinct myeloid or T or B lymphoid lineage precursors. The dataset comprises 24 samples divided into eight sample groups each representing a different lymphoid progenitor cell type isolated from wild-type (+/-) or transgenic (-/-) thymic niches. -/-, Foxn1-deficient genotype; +/-, Foxn1 heterozygous phenotype; DP, CD4/CD8 double-poisztive thymocytes; DN3, CD4/CD8-negative stage 3 thymocytes; SP4, CD4 single-positive thymocytes; SP8, CD8 single-positive thymocytes; B IgM-, IgM surface negative B cells; B IgM+, IgM surface positive B cells; B IgM- -/-, IgM surface negative B cells from Foxn1-deficient genotype.