Project description:The development and function of stem and progenitor cells that produce blood cells are vital in physiology. GATA2 mutations cause immunodeficiency, myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). GATA-2 physiological activities necessitate that it be strictly regulated and cell type-specific enhancers fulfill this role. The +9.5 intronic enhancer harbors multiple conserved cis-elements, and germline mutations of these cis-elements are pathogenic in humans. Since mechanisms underlying how GATA2 enhancer disease mutations impact hematopoiesis and pathology are unclear, we generated mouse models of the enhancer mutations. While a multi-motif mutant was embryonic lethal, a single-nucleotide Ets motif mutant was viable and steady-state hematopoiesis was normal. However, the Ets motif mutation abrogated stem/progenitor cell regeneration following stress. These results reveal a new mechanism in human genetics in which a disease mutation inactivates enhancer regenerative activity, while sparing developmental activity. Mutational sensitization to stress that instigates hematopoietic failure constitutes a paradigm for GATA-2-dependent pathogenesis.
Project description:Hematopoietic stem cells sustain life-long blood production. While they are the known cellular origin of aging-associated myeloid malignancies, such as acute myeloid leukemia (AML), mechanisms driving their malignant transformation have remained elusive. Epigenetic dysregulation following acquired loss-of-function mutations of DNA methyl-cytosine dioxygenase Ten-Eleven Translocation-2 (TET2) occurs frequently in the elderly leading to cytosine hypermethylation in and around DNA binding sites of master transcription factors, including PU.1. Here we show that Tet2 deficient hematopoietic stem and progenitor cells (HSPC) undergo malignant transformation upon compromised PU.1 gene regulation. Leukemic stem and progenitor cells show hypermethylation at PU.1 binding sites and fail to activate PU.1-depenent myeloid enhancers, and are hallmarked by a defined signature of impaired genes shared with human AML. Our study demonstrates that Tet2 and PU.1 cooperate in suppressing leukemogenesis in HSPC and establishes a methylation sensitive PU.1-dependent gene network as a unifying feature in acute myeloid leukemia.
Project description:Hematopoietic stem cells sustain life-long blood production. While they are the known cellular origin of aging-associated myeloid malignancies, such as acute myeloid leukemia (AML), mechanisms driving their malignant transformation have remained elusive. Epigenetic dysregulation following acquired loss-of-function mutations of DNA methyl-cytosine dioxygenase Ten-Eleven Translocation-2 (TET2) occurs frequently in the elderly leading to cytosine hypermethylation in and around DNA binding sites of master transcription factors, including PU.1. Here we show that Tet2 deficient hematopoietic stem and progenitor cells (HSPC) undergo malignant transformation upon compromised PU.1 gene regulation. Leukemic stem and progenitor cells show hypermethylation at PU.1 binding sites and fail to activate PU.1-depenent myeloid enhancers, and are hallmarked by a defined signature of impaired genes shared with human AML. Our study demonstrates that Tet2 and PU.1 cooperate in suppressing leukemogenesis in HSPC and establishes a methylation sensitive PU.1-dependent gene network as a unifying feature in acute myeloid leukemia.
Project description:Hematopoietic stem cells sustain life-long blood production. While they are the known cellular origin of aging-associated myeloid malignancies, such as acute myeloid leukemia (AML), mechanisms driving their malignant transformation have remained elusive. Epigenetic dysregulation following acquired loss-of-function mutations of DNA methyl-cytosine dioxygenase Ten-Eleven Translocation-2 (TET2) occurs frequently in the elderly leading to cytosine hypermethylation in and around DNA binding sites of master transcription factors, including PU.1. Here we show that Tet2 deficient hematopoietic stem and progenitor cells (HSPC) undergo malignant transformation upon compromised PU.1 gene regulation. Leukemic stem and progenitor cells show hypermethylation at PU.1 binding sites and fail to activate PU.1-depenent myeloid enhancers, and are hallmarked by a defined signature of impaired genes shared with human AML. Our study demonstrates that Tet2 and PU.1 cooperate in suppressing leukemogenesis in HSPC and establishes a methylation sensitive PU.1-dependent gene network as a unifying feature in acute myeloid leukemia.
Project description:Acute Myeloid Leukemia (AML) is associated with a number of genetic and epigenetic events that result in malignant transformation of hematopoietic cells. In particular, transcription factors essential for normal hematopoiesis and stem cell function are often found mutated leading to the formation of leukemic stem cells and the accumulation of immature blasts. Among them, translocations involving the mixed lineage leukemia (MLL) gene at chromosome band 11q23 are one of the most commonly events (~10 %) and is associated with poor prognosis in human leukemias. Whereas the downstream effects of MLL-fusion proteins are well established, the modes on which these effects are mediated are still unclear and whether MLL-fusion proteins are dependent on other transcriptional regulators or act alone remains elusive. To investigate this we searched gene expression profiles from patients with MLL-rearranged AML compared with normal hematopoietic progenitor cells for transcriptional regulators and found targets of C/EBPα to be up-regulated in the AML samples, suggesting that C/EBPα might collaborate with MLL-fusion proteins in the initial transformation process. We could show that transformation by MLL-fusion proteins is dependent on C/EBPα activity both in early progenitors as well as in GMPs. In contrast, C/EBPα was found to be indispensable in an already established leukemia. These finding led us to study the early transcriptional changes induced by MLL-ENL expression and we identified a combined C/EBPα / MLL-ENL transcriptional signature. Collectivly, our data shows that C/EBPα configure a proper chromatin state required for MLL-fusions to induce malignant transformation. Histone modification profiles (H3K4me3 and H3K27me3) in haematopoietic progenitor cells (preGM, wild type and Cebpa knock out), and C/EBPα binding in GMP cells
Project description:This is a mathematical model describing the hematopoietic lineages with leukemia lineages, as controlled by end-product negative feedback inhibition. Variables include hematopoietic stem cells, progenitor cells, terminally differentiated HSCs, leukemia stem cells, and terminally differentiated leukemia stem cells.
Project description:Leukemia initiating cells (LICs) of acute myeloid leukemia (AML) may arise from self-renewing hematopoietic stem cells (HSCs) and from committed progenitors. However, it remains unclear how leukemia-associated oncogenes instruct LIC formation from cells of different origins and if differentiation along the normal hematopoietic hierarchy is involved. Here, using murine models with the driver mutations MLL-AF9 or MOZ-TIF2, we found that regardless of the transformed cell types, myelomonocytic differentiation to the granulocyte macrophage progenitor (GMP) stage is critical for LIC generation. Blocking myeloid differentiation through disrupting the lineage-restricted transcription factor C/EBPa eliminates GMPs, blocks normal granulopoiesis, and prevents AML development. In contrast, restoring myeloid differentiation through inflammatory cytokines “rescues” AML transformation. Our findings identify myeloid differentiation as a critical step in LIC formation and AML development, thus guiding new therapeutic approaches. Examination of chromatin accessibility in Cebpa knock-out and control conditions.
Project description:Leukemia initiating cells (LICs) of acute myeloid leukemia (AML) may arise from self-renewing hematopoietic stem cells (HSCs) and from committed progenitors. However, it remains unclear how leukemia-associated oncogenes instruct LIC formation from cells of different origins and if differentiation along the normal hematopoietic hierarchy is involved. Here, using murine models with the driver mutations MLL-AF9 or MOZ-TIF2, we found that regardless of the transformed cell types, myelomonocytic differentiation to the granulocyte macrophage progenitor (GMP) stage is critical for LIC generation. Blocking myeloid differentiation through disrupting the lineage-restricted transcription factor C/EBPa eliminates GMPs, blocks normal granulopoiesis, and prevents AML development. In contrast, restoring myeloid differentiation through inflammatory cytokines “rescues” AML transformation. Our findings identify myeloid differentiation as a critical step in LIC formation and AML development, thus guiding new therapeutic approaches. Primary KSL, CMP, and GMP cells from wildtype controls and C/Ebpa knockouts were used for RNA extraction and hybridization on Affymetrix microarrays. We also compared the microarray samples of leukemic granulocyte macrophage progenitor compartments (L-GMPs) from MLL-AF9 transformed control or cytokine rescued C/EBPa KO leukemic mouse bone marrow and their secondary recipients with those non-Leukemia KSLs and CMPs from MLL-AF9 transduecd KO recipients with no leukemia development.
Project description:Leukemia initiating cells (LICs) of acute myeloid leukemia (AML) may arise from self-renewing hematopoietic stem cells (HSCs) and from committed progenitors. However, it remains unclear how leukemia-associated oncogenes instruct LIC formation from cells of different origins and if differentiation along the normal hematopoietic hierarchy is involved. Here, using murine models with the driver mutations MLL-AF9 or MOZ-TIF2, we found that regardless of the transformed cell types, myelomonocytic differentiation to the granulocyte macrophage progenitor (GMP) stage is critical for LIC generation. Blocking myeloid differentiation through disrupting the lineage-restricted transcription factor C/EBPa eliminates GMPs, blocks normal granulopoiesis, and prevents AML development. In contrast, restoring myeloid differentiation through inflammatory cytokines “rescues” AML transformation. Our findings identify myeloid differentiation as a critical step in LIC formation and AML development, thus guiding new therapeutic approaches. Primary KSL, CMP, and GMP cells from wildtype controls and C/Ebpa knockouts were used for RNA extraction and hybridization on Affymetrix microarrays. We also compared the microarray samples of leukemic granulocyte macrophage progenitor compartments (L-GMPs) from MLL-AF9 transformed control or cytokine rescued C/EBPa KO leukemic mouse bone marrow and their secondary recipients with those non-Leukemia KSLs and CMPs from MLL-AF9 transduecd KO recipients with no leukemia development.
Project description:The comparative characterization of hematopoietic stem cells from healthy stem cell donors and patients with acute myeloid leukemia on a proteome level has the potential to reveal differentially regulated proteins which might be candidates for specific immunotherapy target molecules. Exemplarily, we analyzed the proteome of the cytosolic and the membrane fraction of CD34 and CD123 co-expressing FACS-sorted leukemic progenitors from five patients with acute myeloid leukemia employing mass spectrometry. As a reference, CD34+CD123+ normal hematopoietic progenitor cells from five healthy stem cell donors were analyzed. In this TMT 10-plex labeling based approach 2068 proteins were identified with 256 proteins differentially regulated in one or both cellular compartments. This study demonstrates the feasibility of a mass spectrometry based proteomic approach to detect differentially expressed proteins in two compartment fractions of leukemic stem cells as compared to their healthy stem cell counterparts.