scholarly journals Transgenic expression of JAK2V617F causes myeloproliferative disorders in mice

Blood ◽  
2008 ◽  
Vol 111 (10) ◽  
pp. 5109-5117 ◽  
Author(s):  
Shu Xing ◽  
Tina Ho Wanting ◽  
Wanming Zhao ◽  
Junfeng Ma ◽  
Shaofeng Wang ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Transgenic Mice ◽  
Polycythemia Vera ◽  
Essential Thrombocythemia ◽  
Gene Promoter ◽  
Primary Myelofibrosis ◽  
Myeloproliferative Disorders ◽  
Transgenic Expression ◽  
Cell Counts

Abstract The JAK2V617F mutation was found in most patients with myeloproliferative disorders (MPDs), including polycythemia vera, essential thrombocythemia, and primary myelofibrosis. We have generated transgenic mice expressing the mutated enzyme in the hematopoietic system driven by a vav gene promoter. The mice are viable and fertile. One line of the transgenic mice, which expressed a lower level of JAK2V617F, showed moderate elevations of blood cell counts, whereas another line with a higher level of JAK2V617F expression displayed marked increases in blood counts and developed phenotypes that closely resembled human essential thrombocythemia and polycythemia vera. The latter line of mice also developed primary myelofibrosis-like symptoms as they aged. The transgenic mice showed erythroid, megakaryocytic, and granulocytic hyperplasia in the bone marrow and spleen, displayed splenomegaly, and had reduced levels of plasma erythropoietin and thrombopoietin. They possessed an increased number of hematopoietic progenitor cells in peripheral blood, spleen, and bone marrow, and these cells formed autonomous colonies in the absence of growth factors and cytokines. The data show that JAK2V617F can cause MPDs in mice. Our study thus provides a mouse model to study the pathologic role of JAK2V617F and to develop treatment for MPDs.

scholarly journals Transgenic Expression of JAK2V617F Causes Myeloproliferative Disorders in Mice.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2527-2527
Author(s):  
Shu Xing ◽  
Zhizhuang Joe Zhao
Keyword(s):  
Transgenic Mice ◽  
Myeloproliferative Disorders ◽  
Extramedullary Hematopoiesis ◽  
Transgenic Expression ◽  
Cell Counts ◽  
Serum Erythropoietin Level ◽  
Hyper Sensitivity ◽  
Serum Erythropoietin

Abstract Recently, an acquired mutation of tyrosine kinase JAK2 was found in most patients with myeloproliferative disorders (MPDs) including polycythemia vera (PV), essential thrombocythemia (ET), and idiopathic myelofibrosis. We have generated transgenic mice expressing the mutation enzyme, JAK2V617F, in the hematopoietic system driven by the promoter of the vav gene. The mice are viable and fertile. One line of the transgenic mice expressed a lower level of JAK2V617F and displayed elevated blood cell counts, while the other line expressed a higher level of JAK2V617F and exhibited a marked increase in blood counts and developed phenotypes that closely resembled human ET and PV. The latter line of mice also developed marrow and spleen fibrosis as the animal aged. In general, the transgenic mice had megakaryocytic hyperplasia in the bone morrow and extramedullary hematopoiesis resulting in splenomegaly, and their serum erythropoietin level was also significantly reduced. In vitro colony assays demonstrated that transgenic mice possessed an increased number of hematopoietic progenitor cells in peripheral blood, spleen, and bone marrow and that these cells displayed hyper-sensitivity to growth factors and cytokines. The data prove that JAK2V617F is a cause of MPDs. Our study thus provides a permanent mouse system for further study to define the pathological role of JAK2V617F and to develop treatment for MPDs.

scholarly journals MPL W515 L/K mutations in myeloproliferative neoplasms

2019 ◽  
Vol 20 (1) ◽  
Author(s):  
Sohaila Eldeweny ◽  
Hosny Ibrahim ◽  
Ghada Elsayed ◽  
Mohamed Samra
Keyword(s):  
Bone Marrow ◽  
Polycythemia Vera ◽  
Ethnic Groups ◽  
Essential Thrombocythemia ◽  
Myeloproliferative Neoplasms ◽  
Primary Myelofibrosis ◽  
Myelogenous Leukemia ◽  
Egyptian Population ◽  
Ph Chromosome ◽  
Pathological Variant

Abstract Background Myeloproliferative neoplasms (MPNs) describe a group of diseases involving the bone marrow (BM). Classical MPNs are classified into chronic myelogenous leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). This classification is based on the presence of Philadelphia (Ph) chromosome (BCR/ABL1). CML is BCR/ABL1-positive while PV, ET, and PMF are negative. JAK2 p. Val617Phe pathological variant is the most associated mutation in BCR/ABL1-negative MPNs. The frequency of JAK2 p. Val617Phe is 90–95% in PV patients, 50–60% in ET, and 40–50% in patients with PMF. Studies on MPL gene led to the revelation of a gain of function pathological variants in JAK2 p. Val617Phe-negative myeloproliferative neoplasms (MPNs). MPL p. W515 L/K pathological variants are the most common across all mutations in MPL gene. The prevalence of these pathological variants over the Egyptian population is not clear enough. In the present study, we aimed to investigate the prevalence of MPL p. W515 L/K pathological variants in the Philadelphia (Ph)-negative MPNs over the Egyptian population. Results We have tested 60 patients with Ph-negative MPNs for MPL p. W515 L/K pathological variants. Median age was 51 (22–73) years. No MPL p. W515 L/K pathological variants were detected among our patients. JAK2 p. Val617Phe in PV and PMF patients showed significantly lower frequency than other studies. Splenomegaly was significantly higher in ET patients compared to other studies. Conclusion MPL p. W515 L/K pathological variants are rare across the Egyptian Ph-negative MPNs, and further studies on a large number are recommended. MPN patients in Egypt are younger compared to different ethnic groups.

Changing Concepts of Diagnostic Criteria of Myeloproliferative Disorders and the Molecular Etiology and Classification of Myeloproliferative Neoplasms: From Dameshek 1950 to Vainchenker 2005 and Beyond

2014 ◽  
Vol 133 (1) ◽  
pp. 36-51 ◽  
Author(s):  
Jan Jacques Michiels ◽  
Zwi Berneman ◽  
Wilfried Schroyens ◽  
Hendrik De Raeve
Keyword(s):  
Bone Marrow ◽  
Polycythemia Vera ◽  
Myeloproliferative Neoplasms ◽  
Primary Myelofibrosis ◽  
Myeloproliferative Disorders ◽  
Jak2v617f Mutation ◽  
Wild Type ◽  
Mutation Load ◽  
Molecular Etiology ◽  
Calr Mutations

The Polycythemia Vera Study Group (PVSG) and WHO classifications distinguished the Philadelphia (Ph1) chromosome-positive chronic myeloid leukemia from the Ph1-negative myeloproliferative neoplasms (MPN) essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (MF) or primary megakaryocytic granulocytic myeloproliferation (PMGM). Half of PVSG/WHO-defined ET patients show low serum erythropoietin levels and carry the JAK2V617F mutation, indicating prodromal PV. The positive predictive value of a JAK2V617F PCR test is 95% for the diagnosis of PV, and about 50% for ET and MF. The WHO-defined JAK2V617F-positive ET comprises three ET phenotypes at clinical and bone marrow level when the integrated WHO and European Clinical, Molecular and Pathological (ECMP) criteria are applied: normocellular ET (WHO-ET), hypercellular ET due to increased erythropoiesis (prodromal PV) and hypercellular ET associated with megakaryocytic granulocytic myeloproliferation (EMGM). Four main molecular types of clonal MPN can be distinguished: JAK2V617F-positive ET and PV; JAK2 wild-type ET carrying the MPL515; mutations in the calreticulin (CALR) gene in JAK2/MPL wild-type ET and MF, and a small proportion of JAK2/MPL/CALR wild-type ET and MF patients. The JAK2V617F mutation load is low in heterozygous normocellular WHO-ET. The JAK2V617F mutation load in hetero-/homozygous PV and EMGM is clearly related to MPN disease burden in terms of splenomegaly, constitutional symptoms and fibrosis. The JAK2 wild-type ET carrying the MPL515 mutation is featured by clustered small and giant megakaryocytes with hyperlobulated stag-horn-like nuclei, in a normocellular bone marrow (WHO-ET), and lacks features of PV. JAK2/MPL wild-type, CALR mutated hypercellular ET associated with PMGM is featured by dense clustered large immature dysmorphic megakaryocytes and bulky (cloud-like) hyperchromatic nuclei, which are never seen in WHO-ECMP-defined JAK2V617F mutated ET, EMGM and PV, and neither in JAK2 wild-type ET carrying the MPL515 mutation. Two thirds of JAK2/MPL wild-type ET and MF patients carry one of the CALR mutations as the cause of the third distinct MPN entity. WHO-ECMP criteria are recommended to diagnose, classify and stage the broad spectrum of MPN of various molecular etiologies.

JAK2 V617F Mutation Identifies a Biologically Distinct Subtype of Essential Thrombocythemia Which Resembles Polycythemia Vera.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 253-253 ◽  
Author(s):  
Anthony Green ◽  
Peter Campbell ◽  
Linda Scott ◽  
Georgina Buck ◽  
Keith Wheatley ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Platelet Count ◽  
Polycythemia Vera ◽  
Essential Thrombocythemia ◽  
Response To Therapy ◽  
Jak2 Mutation ◽  
Mutation Status ◽  
Cell Counts ◽  
V617f Mutation

Abstract An acquired V617F mutation in JAK2 occurs in most patients with polycythemia vera (PV) but only half of those with essential thrombocythemia (ET) and idiopathic myelofibrosis. It is not known whether mutation-bearing patients are biologically distinct from those lacking the mutation, or why the same mutation is associated with different phenotypes. Two sensitive PCR-based methods were used to assess the JAK2 mutation status of 806 patients with ET, including 776 from the MRC PT-1 trial and two other prospective studies. The combined cohort provides a unique resource for studying ET, particularly in view of its large size, centralized review of end-points and comprehensive follow-up. The involvement of a large number of secondary and tertiary centers, together with the inclusion of patients in all risk categories, suggest the results are of general relevance. JAK2 mutation status divided the cohort into two distinct subgroups. Mutation-positive patients (53.4%) displayed multiple features resembling PV, with significantly increased hemoglobin levels (p<0.0001), neutrophil counts (p<0.0001), bone marrow erythropoiesis (p=0.001) and granulopoiesis (p=0.005). They suffered more venous thromboses in the year before diagnosis (p=0.04) and during follow-up (p=0.06), together with a higher incidence of polycythemic transformation (p=0.01). To explore the resemblance between V617F-positive ET and PV further, we analysed factors that might constrain erythropoiesis. Compared to mutation-negative patients with ET, mutation-positive patients had lower serum epo (p<0.0001), lower ferritin (p=0.01), and were more likely to be microcytic (p<0.0001). V617F-positive patients were more sensitive to hydroxyurea, requiring lower doses to control platelet count than V617F-negative patients (p<0.0001), a pattern not seen with anagrelide. Despite lower doses of hydroxyurea, V617F-positive patients had greater reductions in hemoglobin, platelet and white cell counts than V617F-negative patients, with no analogous differences noted between V617F-positive and negative patients randomized to anagrelide (p=0.004, p=0.04, p=0.0003 for platelet count, Hb and WCC). Mutation-negative patients did exhibit many clinical and laboratory features characteristic of a myeloproliferative disorder, including cytogenetic abnormalities, hypercellular bone marrow, abnormal megakaryocyte morphology, PRV1 over-expression, growth of epo-independent erythroid colonies, and a risk of myelofibrotic or leukemic transformation. JAK2 mutation status defines two biologically distinct subgroups of ET with differences in presentation, outcome and response to therapy. Our results suggest a model in which V617F-positive ET and PV form a continuum, with the degree of erythrocytosis determined by physiological or genetic modifiers, including iron stores, epo homeostasis, gender and V617F-homozygosity. This concept has major implications for the classification, diagnosis and management of MPDs.

Transgenic Expression of Wild Type JAK2 Suppresses Myeloproliferative Disorder Phenotypes Induced by Mutant JAK2V617F in Mice

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 180-180
Author(s):  
Shu Xing ◽  
Wanming Zhao ◽  
Wanting Tina Ho ◽  
Zhizhuang Joe Zhao
Keyword(s):  
Transgenic Mice ◽  
Myeloproliferative Disorders ◽  
Heterozygous Mutation ◽  
Homozygous Mutation ◽  
Mutant Form ◽  
Dependent Manner ◽  
Wild Type ◽  
Transgenic Expression ◽  
Cell Counts ◽  
Invaluable Tool

Abstract JAK2V617F, a mutant form of tyrosine kinase JAK2, is found in the majority of patients with myeloproliferative disorders (MPDs). It displays increased kinase activity and causes MPD phenotypes in transgenic mice in a transgence dosage-dependent manner. Following our initial generation and characterization of JAK2V617F transgenic mice, we further generated transgenic mice expressing wild type JAK2 by using the same vav promoter employed for JAK2V617F. Three lines of JAK2 transgenic mice were generated. Real time PCR analyses revealed transgene copy numbers of 38, 2, and 1. All these mice are viable and fertile, and they displayed normal blood cell counts. This proves that the V617F mutation but not gene overexpression per se caused MPD phenotypes in JAK2V617F transgenic mice. We then crossed the JAK2 and JAK2V617F transgenic mice to generate JAK2/JAK2V617F double transgenic hybrids. Interestingly, these hybrid mice developed no or mild MPD phenotypes with only a slight increase in blood counts in contrast to the striking elevation observed in JAK2V617F transgenic mice. Expression of wild type JAK2 also blocked the constitutive activation of signal transduction components caused by JAK2V617F. Our data indicates that over-expression of wild type JAK2 suppresses the pathogenic function of mutant JAK2V617F. Therefore, JAK2V617F is not a typical dominant oncogene. Homozygous mutation or in the case of heterozygous mutation, its amplification with concurrent deletion or suppression of wild type JAK2, is required to produce MPD phenotypes. Our transgenic mouse models will serve as an invaluable tool to study the interplay of JAK2 and JAK2V617F and the mechanism by which specific MPD phenotypes develop.

Conditional Expression of Heterozygous or Homozygous Jak2V617F From Its Endogenous Promoter Induces a Polycythemia Vera-Like Disease.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 437-437
Author(s):  
Hajime Akada ◽  
Dongqing Yan ◽  
Haiying Zou ◽  
Robert E. Hutchison ◽  
M. Golam Mohi
Keyword(s):  
Polycythemia Vera ◽  
Conflicts Of Interest ◽  
Gene Dosage ◽  
Primary Myelofibrosis ◽  
Myeloproliferative Disorders ◽  
Serum Levels ◽  
Severe Form ◽  
Downstream Signaling ◽  
Conditional Expression

Abstract Abstract 437 A somatic point mutation (V617F) in the JAK2 tyrosine kinase was found in a majority of patients with polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). However, the contribution of JAK2V617F in these three clinically distinct myeloproliferative disorders (MPDs) remained unclear. To investigate the actual role of JAK2V617F in the pathogenesis of MPDs, we generated an inducible Jak2V617F knock-in mouse, in which the expression of Jak2V617F is under control of the endogenous Jak2 promoter. Expression of heterozygous Jak2V617F evoked all major features of human PV, which included marked increase in hemoglobin and hematocrit, increased red blood cells, leukocytosis, thrombocytosis, splenomegaly, reduced serum levels of erythropoietin (Epo) and Epo-independent erythroid colonies. Homozygous Jak2V617F expression resulted in a more severe form of PV associated with markedly elevated leukocytosis, neutrophilia and thrombocytosis, and a majority of these mice succumbed due to massive cardiac thrombosis. Activation of Stat5, Akt and Erk was significantly enhanced in erythroblast cells expressing homozygous Jak2V617F compared to heterozygous Jak2V617F, suggesting that the degree of activation of downstream signaling pathways would be affected by the Jak2V617F gene dosage. This may also partly explain the severe phenotype in mice expressing homozygous Jak2V617F. We conclude that heterozygous Jak2V617F is sufficient to cause PV, whereas homozygous Jak2V617F increases the severity of PV disease and the risk of thrombosis. Our results also provide strong evidence that Jak2V617F gene dosage does not play a defining role in determining PV versus ET phenotype in this mouse model of MPD. Disclosures: No relevant conflicts of interest to declare.

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