Project description:We report a Jak2V617F knock-in mouse myeloproliferative neoplasm (MPN) model resembling human polycythemia vera (PV). The MPN is serially transplantable and we demonstrate that the hematopoietic stem cell (HSC) compartment has the unique capacity for disease initiation but does not have a selective competitive advantage over wild type HSCs. In contrast, myeloid progenitor populations are expanded and skewed towards the erythroid lineage, but cannot transplant the disease. Treatment with a JAK2 kinase inhibitor ameliorated the MPN phenotype, but did not eliminate the disease-initiating population. These findings provide insights into the consequences of JAK2 activation on HSC differentiation and function and have the potential to inform therapeutic approaches to JAK2V617F positive MPN. LKS cells were isolated from wild type (n=4) and JAK2V617F mutant mice (n=4). RNA was extracted using Qiagen RNeasy Micro Kit according to manufacturers instruction and amplified using NUGEN amplification kit. cDNA was fragmented and biotinylated before hybridization onto Affymetrix Mouse Expression Array 430 2.0.
Project description:We report a Jak2V617F knock-in mouse myeloproliferative neoplasm (MPN) model resembling human polycythemia vera (PV). The MPN is serially transplantable and we demonstrate that the hematopoietic stem cell (HSC) compartment has the unique capacity for disease initiation but does not have a selective competitive advantage over wild type HSCs. In contrast, myeloid progenitor populations are expanded and skewed towards the erythroid lineage, but cannot transplant the disease. Treatment with a JAK2 kinase inhibitor ameliorated the MPN phenotype, but did not eliminate the disease-initiating population. These findings provide insights into the consequences of JAK2 activation on HSC differentiation and function and have the potential to inform therapeutic approaches to JAK2V617F positive MPN.
Project description:The somatic JAK2V617F mutation is found in a majority of patients with myeloproliferative neoplasms (MPN). Chronic inflammation is often associated with MPN, but the role of inflammation in the pathogenesis of MPN remains elusive. Expression of interleukin-1 (IL-1), a key regulator of inflammation, is found elevated in MPN. Here, we show that increased IL-1β enhances myeloid cell expansion and promotes the development of bone marrow (BM) fibrosis in heterozygous Jak2V617F mouse model of MPN. Genetic deletion of IL-1 receptor 1 (IL-1R1) preferentially inhibited the expansion of Jak2 mutant hematopoietic stem/progenitor cells. Furthermore, IL-1R1 deletion or blockade with anti-IL-1R1 antibody significantly reduced leukocytosis and splenomegaly, and markedly inhibited BM fibrosis in homozygous Jak2V617F mutant mice. Collectively, our results suggest that IL-1 signaling plays an important role in progression to BM fibrosis in MPN, and targeting of IL-1R1 could be a useful strategy for the treatment of myelofibrosis.
Project description:Cardiovascular events are the leading cause of death in patients with JAK2V617F myeloproliferative neoplasms. Their mechanisms are poorly understood. To investigate the role of microvesicles in these events, we performed a proteomic analysis of microvesicles derived from red blood cells from mice with a myeloproliferative neoplasms (Jak2V617F Flex/WT ;VE-cadherin-Cre) vs. littermate controls.
Project description:Myelofibrosis (MF) is the deadliest form of myeloproliferative neoplasm (MPN). Pim1 expression is significantly elevated in MPN/MF hematopoietic progenitors. So, we investigated the role of Pim1 in myelofibrosis. We show that genetic ablation of Pim1 blocked the development of myelofibrosis induced by Jak2V617F and MPLW515L. Pharmacologic inhibition of Pim1 with a second-generation Pim kinase inhibitor TP-3654 significantly reduced leukocytosis, splenomegaly and attenuated bone marrow fibrosis in Jak2V617F and MPLW515L mouse models of MF. Combined treatment of TP-3654 and Ruxolitinib resulted in greater reduction of spleen size, normalization of blood leukocyte counts and abrogation of bone marrow fibrosis in murine models of MF. TP-3654 treatment also preferentially inhibited Jak2V617F mutant hematopoietic progenitors in mice. Our results suggest that Pim1 plays an important role in the pathogenesis of MF, and inhibition of Pim1 with TP-3654 might be useful for treatment of MF.
Project description:Mutant JAK2V617F is found in majority of patients with myeloproliferative neoplasm. While heterozygous JAK2V617F induced an ET-like phenotype, JAK2V617F homozygosity drives an severe PV-like phenotype in knock-in mice. HSCs from mice with homozygous JAK2V617F expression show impaired self-renewal in transplants. To understand the molecular mechanisms involved this HSC functional defect, microarray was performed on isolated LT-HSCs from mice expressing wildtype, heterozygous and homozygous expression of mutant JAK2.
Project description:Janus kinases (JAKs) mediate cytokine signaling, cell growth and hematopoietic differentiation. Gain-of-function mutations activating JAK2 signaling are seen in the majority of myeloproliferative neoplasm (MPN) patients, most commonly due to the JAK2V617F driver allele. While clinically-approved JAK inhibitors improve symptoms and outcomes in MPNs, remissions are rare, and mutant allele burden does not substantively change with chronic JAK inhibitor therapy in most patients. This has been postulated to be due to incomplete dependence on constitutive JAK/STAT signaling, alternative signaling pathways, and/or the presence of cooperating disease alleles; however we hypothesize this is due to the inability of current JAK inhibitors to potently and specifically abrogate mutant JAK2 signaling. We therefore developed a conditionally inducible mouse model allowing for sequential activation, and then inactivation, of Jak2V617F from its endogenous locus using a Dre-rox/Cre-lox dual orthogonal recombinase system. Deletion of oncogenic Jak2V617F abrogates the MPN disease phenotype, induces mutant-specific cell loss including in hematopoietic stem/progenitor cells, and extends overall survival to an extent not observed with pharmacologic JAK inhibition. Furthermore, reversal of Jak2V617F in MPN cells with antecedent loss of Tet2 abrogates the MPN phenotype and inhibits mutant stem cell persistence suggesting cooperating epigenetic-modifying alleles do not alter dependence on mutant JAK/STAT signaling. Our results suggest that mutant-specific inhibition of JAK2V617F represents the best therapeutic approach for JAK2V617F-mutant MPN and demonstrate the therapeutic relevance of a dual-recombinase system to assess mutant-specific oncogenic dependencies in vivo.
Project description:An activating JAK2V617F mutation has been found in ∼50% patients with myelofibrosis (MF). Inactivating mutations in histone methyltransferase enhancer of zeste homolog 2 (EZH2) also have been observed in patients with MF. Interestingly, inactivating EZH2 mutations are often associated with JAK2V617F mutation in MF, although their contributions in the pathogenesis of MF remain elusive. To determine the effects of concomitant loss of EZH2 and JAK2V617F mutation in hematopoiesis, we generated Ezh2-deficient Jak2V617F-expressing mice. Whereas expression of Jak2V617F alone induced a polycythemia vera-like disease, concomitant loss of Ezh2 significantly reduced the red blood cell and hematocrit parameters but increased the platelet counts in Jak2V617F knock-in mice. Flow cytometric analysis showed impairment of erythroid differentiation and expansion of megakaryocytic precursors in Ezh2-deficient Jak2V617F mice. Moreover, loss of Ezh2 enhanced the repopulation capacity of Jak2V617F-expressing hematopoietic stem cells. Histopathologic analysis revealed extensive fibrosis in the bone marrow (BM) and spleen of Ezh2-deleted Jak2V617F mice. Transplantation of BM from Ezh2-deleted Jak2V617F mice into wild-type animals resulted in even faster progression to MF. Gene expression profiling and chromatin immunoprecipitation sequence analysis revealed that S100a8, S100a9, Ifi27l2a, and Hmga2 were transcriptionally derepressed, and the H3K27me3 levels in these gene promoters were significantly reduced on Ezh2 deletion in hematopoietic progenitors of Jak2V617F mice. Furthermore, overexpression of S100a8, S100a9, Ifi27l2a, or Hmga2 significantly increased megakaryocytic colonies in the BM of Jak2V617F mice, indicating a role for these Ezh2 target genes in altered megakaryopoiesis involved in MF. Overall, our results suggest that loss of Ezh2 cooperates with Jak2V617F in the development of MF in Jak2V617F-expressing mice.
Project description:Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) consist of primary myelofibrosis (PMF), polycythemia vera (PV), essential thrombocythemia (ET) In this dataset, we compare the gene expression data of patients JAK2V617F vs. CALR-mutated MPN patients.
Project description:Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) consist of primary myelofibrosis (PMF), polycythemia vera (PV), essential thrombocythemia (ET) and seconday myelofibrosis (pPV-MF or pET-MF) In this dataset, we compare the gene expression data of bone marrow (BM) or peripheral blood (PB) mononuclear cells of CD34+ cells from JAK2V617F mutated patients vs. healthy donors