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: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:Background: Patients with JAK2V617F-positive myeloproliferative neoplasms (MPNs) and clonal hematopoiesis of indeterminate potential (CHIP) face a significantly elevated risk of cardiovascular diseases (CVDs). Endothelial cells (ECs) carrying the JAK2V617F mutation have been detected in many MPN patients. In this study, we investigated the molecular basis for the high incidence of cardiovascular complications in MPN patients. Methods: We investigated the impact of endothelial JAK2V617F mutation on CVD development using both transgenic murine models and MPN patient-derived induced pluripotent stem cell lines. Results and Conclusions: Our investigations revealed that JAK2V617F mutant ECs promote CVDs by impairing endothelial function and undergoing endothelial-to-mesenchymal transition (EndMT). Importantly, we discovered that inhibiting the endothelial thrombopoietin receptor MPL suppressed JAK2V617F-induced EndMT and prevented cardiovascular dysfunction caused by mutant ECs. Notably, the endothelial MPL receptor is not essential for the normal physiological regulation of blood cell counts and cardiac function, rendering it a promising therapeutic target for preventing or ameliorating cardiovascular complications in patients with MPNs.
Project description:V617F driver mutation of JAK2 is the leading cause of the Philadelphia-chromosome-negative myeloproliferative neoplasms (MPNs). Loss of Plek2 ameliorated JAK2V617F-induced myeloproliferative phenotypes including erythrocytosis, neutrophilia, thrombocytosis, and splenomegaly, thereby reverting the widespread vascular occlusions and lethality of JAK2V617F knockin mice. To reveal the role of Plek2 in the pathogenesis of JAK2V617F-induced MPNs and the detail mechanisms of its rescue, we performed RNA sequencing to analyze the gene expression profiles change between JAK2V617F/+ Plek2+/+ and JAK2V617F/+ Plek2-/- erythroblasts and hematopoietic stem/progenitor cells.
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:This SuperSeries is composed of the following subset Series: GSE21948: High Density custom Agilent 44K CGH array analysis of 7q and TET2 region in myelodysplastic/myeloproliferative neoplasms GSE21990: Affymetrix SNP 6.0 array data for myelodysplastic/myeloproliferative neoplasms Refer to individual Series
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:Myeloproliferative neoplasms (MPN) are clonal hematopoietic diseases that include essential thrombocytosis (ET), polycythemia vera (PV) and primary myelofibrosis (PMF) as well as BCR-ABL+ chronic myelogenous leukemia (CML). In the past several years, studies with cDNA microarrays have defined patterns of gene expression corresponding to specific molecular abnormalities, oncologic phenotypes, and clinical outcomes in hematologic malignancies. This study was aimed at the description of a gene expression signature in MPN which would eventually present a new pathogenetic approaching and also diagnostic as well as prognostic information. Using cDNA microarray analysis, involving 25,100 unique genes, we studied the gene expression profile of the pluripotent hematopoietic CD34+ stem cells and mature granulocytes obtained from peripheral blood of ET, PV, PMF and CML patients compared with healthy individuals. The average number of CD34+ cells (cells/µl) in peripheral blood was approximately 6 in PV and ET, 111 in PMF and 2880 in CML as measured by flow cytometry. A somatic point mutation JAK2V617F was detected in 93% of PV, 73% of PMF and 55% of ET patients within genetically homogenous population. The homozigosity for JAK2V617F mutation was the highest in PV (60%), less prominent in PMF (42%) and low in ET (11%) patients. The JAK2V617F mutation negative patients were also negative for exon 12 mutations. Approximately 420, 680 and 1130 genes had unique expression among CD34+ cells of ET, PV and PMF patients, respectively. In addition comparing to healthy controls, ET, PV, PMF and CML patients showed difference in 840, 1180, 1160 and 2050 expressed genes, respectively. Furthermore, we studied EPO and JAK-STAT signaling pathways related genes expression in MPN. The FOS, RAF1 and JAK2 gene expression, related to EPO signaling pathway, was elevated in ET, PV, PMF and reduced in CML comparing to healthy controls. Related to these genes, the JAK2V617F mutation homozygous and heterozygous patients generally displayed more significant differences comparing to patients with no mutation. STAT5 gene expression was decreased in all MPN patients. CSF3R, STAT1 and STAT3 gene expression, related to JAK-STAT signaling pathway, was elevated in ET, PV, PMF and reduced in CML comparing to healthy controls. CREBBP gene expression was reduced in CD34+ cells of ET, PV and PMF patients, but during maturation it enhanced expression in granulocytes. In conclusion, molecular profiling of CD34+ cells and granulocytes revealed a certain number of genes with changed expression that, beyond their recognized function in disease pathogenesis, can be related to patients’ clinical characteristics and may have an imminent prognostic relevance.