Ubiquitination is a post-translational mechanism of control of diverse cellular processes. We focus here on the ubiquitin ligase Fbw7, a recently identified hematopoietic tumor suppressor that can target for degradation several important oncogenes including Notch1, c-Myc and cyclin E. We have generated conditional Fbw7 knock-out animals and inactivated the gene in hematopoietic stem cells (HSC) and their differentiated progeny. Deletion of Fbw7 specifically and rapidly affects the HSC compartment in a cell-autonomous manner. Fbw7-/- HSCs show defective maintenance of quiescence, leading to impaired self-renewal and a severe loss of competitive repopulating capacity. Furthermore, Fbw7-/- HSC are unable to colonize the thymus leading to a profound depletion of T cell progenitors. Deletion of Fbw7 in bone marrow stem cells and progenitors leads to the stabilization of c-Myc, a transcription factor previously implicated in HSC self-renewal. On the other hand, neither Notch1 nor cyclin E are stabilized in the bone marrow of Fbw7 deficient mice. Genome-wide transcriptome studies of Fbw7-/- HSC and hematopoietic progenitors indicate that Fbw7 controls, through the regulation of HSC cell cycle entry, the global transcriptional signature that is associated with the quiescent, self-renewing HSC phenotype.
Control of hematopoietic stem cell quiescence by the E3 ubiquitin ligase Fbw7.
No sample metadata fields
View Samplescompare the gene expression profile between irradiated Lin-Sca-1+c-Kit+ (LSK) cells from mouse bone marrow reconstituted with wild type and necdin null fetal liver cells
Necdin, a p53 target gene, regulates the quiescence and response to genotoxic stress of hematopoietic stem/progenitor cells.
Specimen part, Treatment
View SamplesThe hematological malignancies classified as Mixed Lineage leukemias (MLL) harbor fusions of the MLL1 gene to partners that are members of transcriptional elongation complexes. MLL-rearranged leukemias are associated with extremely poor prognosis and response to conventional therapies and efforts to identify molecular targets are urgently needed. Using mouse models of MLL-rearranged acute myeloid leukemia (AML), here we show that genetic inactivation or small molecule inhibition of the protein arginine methyltransferase PRMT5 exhibit anti-tumoral activity in MLL-fusion protein driven transformation. Genome wide transcriptional analysis revealed that inhibition of PRMT5 methyltransferase activity overrides the differentiation block in leukemia cells without affecting the expression of MLL-fusion direct oncogenic targets. Furthermore, we find that this differentiation block is mediated by transcriptional silencing of the cyclin-dependent kinase inhibitor p21 (CDKN1a) gene in leukemia cells. Our study provides pre-clinical rationale for targeting PRMT5 using small molecule inhibitors in the treatment of leukemias harboring MLL-rearrangements. Overall design: RNA-seq data from 72h-treated DMSO and EPZ 015666 (PRMT5i) MLL-ENL/NrasG12D leukemia cells, three independent replicates.
Genetic deletion or small-molecule inhibition of the arginine methyltransferase PRMT5 exhibit anti-tumoral activity in mouse models of MLL-rearranged AML.
Specimen part, Treatment, Subject
View SamplesThe Hedgehog (Hh) signaling pathway is a developmentally conserved regulator of stem cell function. Several reports suggested that Hh signaling is an important regulator of hematopoietic stem cell (HSC) maintenance and differentiation. Here we test this hypothesis in vivo using both gain- and loss-of-function Hh genetic models. Surprisingly, our studies demonstrate that conditional Smoothened (Smo) deletion or over-activation has no significant effects on adult HSC self-renewal and function. Moreover, they indicate a lack of synergism between the Notch and Hh pathways in HSC function, as RBPJ- and Smo-deficiency do not affect hematopoiesis. In agreement with this notion, detailed genome-wide transcriptome analysis reveals that silencing of Hh signaling does not significantly alter the HSC-specific gene expression signature. Our studies demonstrate that the Hh signaling pathway is dispensable for adult HSC function and suggest that the Hh pathway can be targeted in future clinical trials addressing the effect of Hh inhibition on leukemia-initiating cell maintenance.
Hedgehog signaling is dispensable for adult hematopoietic stem cell function.
Sex
View SamplesEpigenetic regulation of key transcriptional programs is a critical mechanism that controls hematopoietic development and thus aberrant expression patterns or mutations in epigenetic regulators occur frequently in hematologic malignancies. We demonstrate that the Polycomb protein L3MBTL1, which is monoallelically deleted in 20q- myeloid malignancies, represses the ability of stem cells to drive hematopoietic-specific transcriptional programs by regulating the expression of SMAD5 and impairing its recruitment to target regulatory regions. Indeed, knock-down of L3MBTL1 promotes the development of hematopoiesis and impairs neural cell fate in human pluripotent stem cells. We also found a role for L3MBTL1 in regulating SMAD5 target gene expression in mature hematopoietic cell populations, thereby affecting erythroid differentiation. Taken together, we have identified epigenetic priming of hematopoietic-specific transcriptional networks, which may assist in the development of therapeutic approaches for patients with anemia.
The polycomb group protein L3MBTL1 represses a SMAD5-mediated hematopoietic transcriptional program in human pluripotent stem cells.
Cell line
View SamplesAE9aId1fl/flCreER cells treated with the control vehicle, CBD or 4-OHT Overall design: We treated AE9aId1fl/flCreER leukemia with 0.1 µM 4-hydroxytamoxifen (4-OHT) for 48 hours or the Id1 inhibitor CBD (at 15 µM) for 16 hours, and isolated RNA for RNA-seq analysis.
Regulation of AKT signaling by Id1 controls t(8;21) leukemia initiation and progression.
No sample metadata fields
View Samplescompare the gene expression profile between cep701 treated HEL cells with shPRMT5 knockingdown HEL cells. HEL cells contain homologous alells with mutation Jak2V617F. We found JAK2V617F can inactivate PRMT5 activity by directly phosphorylating PRMT5 through histone methylation.
JAK2V617F-mediated phosphorylation of PRMT5 downregulates its methyltransferase activity and promotes myeloproliferation.
Cell line, Treatment
View SamplesDefining the role of epigenetic regulators in normal hematopoiesis has become critically important, as recurrent mutations or aberrant expression of these genes has been identified in both myeloid and lymphoid hematological malignancies. We have found that PRMT4, a type I arginine methyltransferase, whose function in normal and malignant hematopoiesis is unknown, is overexpressed in AML patient samples. In support of an oncogenic role for PRMT4, we find that its overexpression blocks the myeloid differentiation of human stem/progenitor cells (HSPCs) while its knockdown (KD) is sufficient to induce myeloid differentiation of HSPCs and multiple AML cell lines. Although classically thought of as a co-activator, we found that PRMT4 functions to repress the expression of miR-223 in HSPCs via the methylation of RUNX1, which triggers the assembly of a multi-protein repressor complex that includes DPF2. As part of a feedback loop, PRMT4 expression is repressed post-transcriptionally by miR-223 during the normal differentiation process. These data reveal an unidentified role of PRMT4 in myeloid differentiation and its unexpected repressive role in transcriptional regulation. Furthermore, depletion of PRMT4 results in the differentiation of myeloid leukemia cells in vitro and their decrease proliferation in vivo. Thus, targeting PRMT4 holds potential as a novel therapy for acute myelogenous leukemia. Overall design: Purified human primary CD34+ cells were transduced with lentiviruses carrying PRMT4KD or scramble control shRNAs. Total RNA was extrated. RNAseq was performed to identify target genes that are regulated by PRMT4. Experiments were performed in triplicate.
PRMT4 blocks myeloid differentiation by assembling a methyl-RUNX1-dependent repressor complex.
Specimen part, Subject
View SamplesGene expression analysis, a) comparing isogenic karyotypically normal iPSCs to del7q-iPSCs, b) comparing del7q-iPSCs to spontaneously corrected iPSCs. The chr7q deletion results in reduced expression levels of a large number of genes in the chr7q deleted region
Functional analysis of a chromosomal deletion associated with myelodysplastic syndromes using isogenic human induced pluripotent stem cells.
Specimen part, Cell line
View SamplesASXL1 is frequently mutated in a spectrum of myeloid malignancies with poor prognosis. Loss of Asxl1 leads to myelodysplastic syndrome-like disease in mice, however, the underlying molecular mechanisms remain unclear. Here, we report that ASXL1 interacts with the cohesin complex, which has been shown to guide sister chromotid segregation and to regulate gene expression. Loss of Asxl1 impairs the cohesin function as reflected by an impaired telophase chromatid disjunction in hematopoietic cells. ChIP-seq data revealed that ASXL1, RAD21 and SMC1A share 93% of genomic binding sites at promoter regions in lineage-cKit+ (LK) cells. We have showed that loss of Asxl1 reduced the genome binding of RAD21 and SMC1A, and altered the expression of ASXL1/cohesin target genes in LK cells. Our study underscores the ASXL1-cohesin interaction as a novel means to maintain normal sister chromatid separation and to regulate gene expression in hematopoietic cells. Overall design: The DEG genes'' relation with the changes of ASXL1 peaks and Cohesin peaks changes
ASXL1 interacts with the cohesin complex to maintain chromatid separation and gene expression for normal hematopoiesis.
Specimen part, Cell line, Subject
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