Project description:Leukemias are characterized by bone marrow failure due to oncogenic mutations of hematopoietic stem cells (HSC) or blood precursor cells. HSC differentiation and self-renewal properties are tightly regulated by Polycomb group (PcG) proteins, a well-characterized family of transcriptional epigenetic regulators. PcG proteins form two canonical complexes: Polycomb repressive complex 1 (PRC1), and Polycomb repressive complex 2 (PRC2).CBX proteins link the activity of PRC1 with PRC2, serving as critical regulators of PcG-mediating activity. While the functional role of some CBX proteins in cancer has been largely explored, recent reports support the specific role of CBX2 in human tumors, thus it represent a promising new target for anti-cancer strategies. To date, chromodomain inhibitors have been identified for CBX7 , but no molecules inhibiting CBX2 have been described. Nevertheless, different chromatin-modulating drugs such as histone deacetylase inhibitors (HDACi) are reported to regulate CBX2 targets on chromatin, suggesting that HDACi might be used to indirectly modulate aberrant effects of CBX2 in cancer. We describe a novel SAHA-mediated mechanism of CBX2 post-translational regulation. We found that CBX2 undergoes SAHA-induced SUMO2/3 modification and that CBX2 SUMOylation promotes its ubiquitination and proteasome-dependent degradation. We also identified the specific molecular pathway and key players regulating CBX2 stability, demonstrating that CBX4 and RNF4 act as the E3 SUMO and E3 ubiquitin ligase, respectively. Additionally, CBX2-depleted leukemic cells display impaired proliferation, showing that CBX2 is required for leukemia cell clonogenicity. Our study provides the first evidence of a non-canonical SAHA-mediated anti-tumorigenic activity via CBX2 SUMOylation and degradation
Project description:Hematopoietic stem cells (HSCs) represent a rare population of cells residing in the Bone Marrow (BM) at the top of hematopoietic hierarchy. A critical balance is maintained between self-renewal and lineage differentiation of HSCs to maintain hematopoietic homeostasis. With aging, this balance is altered with an increase of self-renewal long term HSCs and a myeloid biased differentiation, which favors the appearance of myeloid leukemias and anemias. This experiment aims to understand molecular mechanisms that cause this aged-related disequilibrium in the mouse. To this end, we generated single cell RNA-seq data from pools of young and old hematopoietic stem and progenitor cells (HSPCs), isolated from mouse BMs.
Project description:Control of oxidative stress in the bone marrow (BM) is key for maintaining the balance between self-renewal, proliferation, and differentiation of hematopoietic cells. Breakdown of this regulation can lead to diseases characterized by BM failure such as the myelodysplastic syndromes (MDS). To better understand the role of oxidative stress in MDS development, we compared protein carbonylation as an oxidative stress marker in BM of patients with MDS and control subjects, and also patients with MDS under treatment with the iron chelator deferasirox.
Project description:Hematopoietic stem cells (HSCs) must balance self-renewal and lineage differentiation to regenerate the hematopoietic system throughout life. HSCs exhibit lineage-associated gene expression that keeps them responsive to demands of mature blood production. However, it is not known whether this process, termed lineage priming, directly influences HSC self-renewal. We investigated the link between stemness and lineage priming by attenuating the early lymphoid transcription factor E47 through ID2 over-expression (OE). Transcriptional profiling of ID2 OE HSCs showed down regulation of B-cell factors including EBF1 and FOXO1 with a concomitant increase in stemness programs and myeloerythroid factors including CEBPA and GATA1. This resulted in myeloid commitment bias from the earliest stages of differentiation. HSC self-renewal was strongly affected by this lineage perturbation resulting in an 11-fold expansion of HSCs. Thus, early lymphoid transcription factors antagonize human HSC self-renewal, providing a direct link between differentiation program priming and the maintenance of stem cell self-renewal. Three independent lineage depleted CB samples were transduced with P-CTRL or P-ID2 and injected into 5 mice (30 mice total). From every group of 5 mice, human lin- cells were isolated and GFP+CD34+CD38-CD45RA- HSPCs were sorted by FACS.
Project description:Hematopoietic stem cells (HSCs) must balance self-renewal and lineage differentiation to regenerate the hematopoietic system throughout life. HSCs exhibit lineage-associated gene expression that keeps them responsive to demands of mature blood production. However, it is not known whether this process, termed lineage priming, directly influences HSC self-renewal. We investigated the link between stemness and lineage priming by attenuating the early lymphoid transcription factor E47 through ID2 over-expression (OE). Transcriptional profiling of ID2 OE HSCs showed down regulation of B-cell factors including EBF1 and FOXO1 with a concomitant increase in stemness programs and myeloerythroid factors including CEBPA and GATA1. This resulted in myeloid commitment bias from the earliest stages of differentiation. HSC self-renewal was strongly affected by this lineage perturbation resulting in an 11-fold expansion of HSCs. Thus, early lymphoid transcription factors antagonize human HSC self-renewal, providing a direct link between differentiation program priming and the maintenance of stem cell self-renewal.
Project description:The hematopoietic system is maintained throughout life by hematopoietic stem cells that are capable of differentiation to all hematopoietic lineages. An intimate balance between self-renewal, differentiation, and quiescence is required to maintain hematopoiesis. Disruption of this balance can result in hematopoietic malignancy, including acute myeloid leukemia (AML). FBXO9, from the F-box ubiquitin E3 ligases, is down-regulated in patients with AML compared to normal bone marrow. FBXO9 is a substrate recognition component of the Skp1-Cullin-F-box (SCF)-type E3 ligase complex. FBXO9 is highly expressed in hematopoietic stem and progenitor populations, which contain the tumor-initiating population in AML. In AML patients, decrease in FBXO9 expression is most pronounced in patients with the inversion of chromosome 16 (Inv(16)), a rearrangement that generates the transcription factor fusion gene, CBFB-MYH11. To study FBXO9 in malignant hematopoiesis, we generated a conditional knockout mouse model using a novel CRISPR/Cas9 strategy. Our data shows that deletion of Fbxo9 in mice expressing Cbfb-MYH11 leads to markedly accelerated and aggressive leukemia development. In addition, we find loss of FBXO9 leads to increased proteasome expression and tumors are more sensitive to bortezomib suggesting that FBXO9 expression may predict patient response to bortezomib treatment.
Project description:Elucidation of the molecular cues required to balance adult stem cell self-renewal and differentiation is critical for advancing cellular therapies. Herein, we report that the hematopoietic stem cell (HSC) self-renewal agonist UM171 triggers a balanced pro- and anti-inflammatory/detoxification network that relies on NFKB activation and protein C receptor-dependent ROS detoxification, respectively. We demonstrate that within this network, EPCR serves as a critical protective component as its deletion hypersensitizes primitive hematopoietic cells to pro-inflammatory signals and ROS accumulation resulting in compromised stem cell function. Conversely, abrogation of the pro-inflammatory activity of UM171 through treatment with dexamethasone, cAMP elevating agents or NFKB inhibitors abolishes EPCR upregulation and HSC expansion. Together, these results show that UM171 stimulates ex vivo HSC expansion by establishing a critical balance between key pro- and anti-inflammatory mediators of self-renewal.
Project description:The transcription factor Runx1 is essential for the establishment of definitive hematopoiesis during embryonic development. In adult blood homeostasis, Runx1 plays a pivotal role in the maturation of lymphocytes and megakaryocytes. Furthermore, Runx1 is required for the regulation of hematopoietic stem and progenitor cell (HSPC) pools. However, how Runx1 orchestrates self-renewal and lineage choices in combination with other factors is not well understood. Here we describe a genome-scale RNAi screen to detect genes that cooperate with Runx1 in regulating HSPCs. We identify the polycomb group protein Pcgf1 as an epigenetic regulator involved in hematopoietic cell differentiation. We show that simultaneous depletion of Runx1 and Pcgf1 allows sustained self-renewal while blocking differentiation of HSPCs in vitro. We find an upregulation of HoxA cluster genes upon Pcgf1 knockdown that possibly accounts for the increase in self-renewal. Further, our data suggest that cells lacking both Runx1 and Pcgf1 are blocked at an early progenitor stage, indicating that a concerted action of the transcription factor Runx1 together with the epigenetic repressor Pcgf1 is necessary for terminal differentiation. Thus, our work discovers a genetic link between transcriptional and epigenetic regulation that is required for hematopoietic differentiation. Hematopoietic stem and precursor cells freshly isolated from mice were transduced with an shRNA targeting Pcgf1 or a control shRNA. Cells were selected with puromycin for 36 h before total mRNA was isolated.
Project description:The balance of self-renewal and differentiation is crucial to ensure the homeostasis of the hematopoietic system, and is a key hallmark of hematopoietic stem cells (HSCs); however, the underlying molecular pathways are not completely understood, including the role of micro-RNAs. To assess micro-RNA contributions, we performed micro-RNA profiling of HSCs and their immediate downstream progeny multi-potent progenitors (MPPs) from wild type control and Pbx1-conditional knockout mice, whose HSCs display a profound self-renewal defect.
Project description:MTD project_description Inflammation and decreased stem cell function characterize organism aging, yet the relationship between these factors remains incompletely understood. This study shows that aged hematopoietic stem and progenitor cells exhibit increased ground-stage NF-κB activity, which enhances their responsiveness to undergo differentiation and loss of self-renewal in response to inflammation. The study identifies Rad21/cohesin as a critical mediator of NF-κB signals, by increasing chromatin accessibility of inter-/intra-genic and enhancer regions. Rad21/NF-κB are required for normal differentiation, but limit self-renewal of hematopoietic stem cells (HSCs) during aging and inflammation in an NF-κB dependent manner. HSCs from aged mice fail to downregulate Rad21/cohesin and inflammation/differentiation inducing signals in the resolution phase after acute inflammation. and The inhibition of cohesin/NF-κB is sufficient to revert the hypersensitivity of aged HSPCs to inflammation-induced differentiation. During aging, myeloid-biased HSCs with disrupted and naturally occurring reduced expression of Rad21/cohesin are increasingly selected over lymphoid-biased HSCs. Together, Rad21/cohesin mediated NF-κB signaling limits HSPC function during aging and selects for cohesin deficient HSCs with myeloid skewed differentiation.