scholarly journals Platelet Dysfunction and Thrombosis in JAK2 V617F -Mutated Primary Myelofibrotic Mice

2020 ◽  
Vol 40 (10) ◽  
Author(s):  
Shinobu Matsuura ◽  
Cristal R. Thompson ◽  
Mostafa Elmokhtra Belghasem ◽  
Roelof H. Bekendam ◽  
Andrew Piasecki ◽  
...  
Keyword(s):  
Mouse Model ◽  
Platelet Activation ◽  
Vascular Injury ◽  
Thrombus Formation ◽  
Myeloproliferative Neoplasms ◽  
Primary Myelofibrosis ◽  
Dense Granule ◽  
Janus Kinase ◽  
Moderate Increase ◽  
Janus Kinase 2

Objective: The risk of thrombosis in myeloproliferative neoplasms, such as primary myelofibrosis varies depending on the type of key driving mutation (JAK2 [janus kinase 2], CALR [calreticulin], and MPL [myeloproliferative leukemia protein or thrombopoietin receptor]) and the accompanying mutations in other genes. In the current study, we sought to examine the propensity for thrombosis, as well as platelet activation properties in a mouse model of primary myelofibrosis induced by JAK2 V617F (janus kinase 2 with valine to phenylalanine substitution on codon 617) mutation. Approach and Results: Vav1-hJAK2 V617F transgenic mice show hallmarks of primary myelofibrosis, including significant megakaryocytosis and bone marrow fibrosis, with a moderate increase in red blood cells and platelet number. This mouse model was used to study responses to 2 models of vascular injury and to investigate platelet properties. Platelets derived from the mutated mice have reduced aggregation in response to collagen, reduced thrombus formation and thrombus size, as demonstrated using laser-induced or FeCl 3 -induced vascular injury models, and increased bleeding time. Strikingly, the mutated platelets had a significantly reduced number of dense granules, which could explain impaired ADP secretion upon platelet activation, and a diminished second wave of activation. Conclusions: Together, our study highlights for the first time the influence of a hyperactive JAK2 on platelet activation-induced ADP secretion and dense granule homeostasis, with consequent effects on platelet activation properties.

scholarly journals STAT5 is Expressed in CD34+/CD38− Stem Cells and Serves as a Potential Molecular Target in Ph-Negative Myeloproliferative Neoplasms

Cancers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1021 ◽  
Author(s):  
Emir Hadzijusufovic ◽  
Alexandra Keller ◽  
Daniela Berger ◽  
Georg Greiner ◽  
Bettina Wingelhofer ◽  
...  
Keyword(s):  
Stem Cells ◽  
Myeloproliferative Neoplasms ◽  
Jak2 V617f ◽  
Primary Myelofibrosis ◽  
Janus Kinase ◽  
Signaling Cascades ◽  
Nuclear Compartment ◽  
Downstream Signaling ◽  
Direct Targeting ◽  
Calr Mutations

Janus kinase 2 (JAK2) and signal transducer and activator of transcription-5 (STAT5) play a key role in the pathogenesis of myeloproliferative neoplasms (MPN). In most patients, JAK2 V617F or CALR mutations are found and lead to activation of various downstream signaling cascades and molecules, including STAT5. We examined the presence and distribution of phosphorylated (p) STAT5 in neoplastic cells in patients with MPN, including polycythemia vera (PV, n = 10), essential thrombocythemia (ET, n = 15) and primary myelofibrosis (PMF, n = 9), and in the JAK2 V617F-positive cell lines HEL and SET-2. As assessed by immunohistochemistry, MPN cells displayed pSTAT5 in all patients examined. Phosphorylated STAT5 was also detected in putative CD34+/CD38− MPN stem cells (MPN-SC) by flow cytometry. Immunostaining experiments and Western blotting demonstrated pSTAT5 expression in both the cytoplasmic and nuclear compartment of MPN cells. Confirming previous studies, we also found that JAK2-targeting drugs counteract the expression of pSTAT5 and growth in HEL and SET-2 cells. Growth-inhibition of MPN cells was also induced by the STAT5-targeting drugs piceatannol, pimozide, AC-3-019 and AC-4-130. Together, we show that CD34+/CD38− MPN-SC express pSTAT5 and that pSTAT5 is expressed in the nuclear and cytoplasmic compartment of MPN cells. Whether direct targeting of pSTAT5 in MPN-SC is efficacious in MPN patients remains unknown.

Endobrevin/VAMP-8-Mediated Dense Granule Release Is Required for Efficient Thrombus Formation in Vivo.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1836-1836
Author(s):  
Price S. Blair ◽  
Qiansheng Ren ◽  
Gwenda J. Graham ◽  
James R. Dilks ◽  
Sidney W. Whiteheart ◽  
...  
Keyword(s):  
Vascular Injury ◽  
Thrombus Formation ◽  
Dense Granule ◽  
Wild Type ◽  
Platelet Accumulation ◽  
Induced Aggregation ◽  
Kinetics Of ◽  
Granule Release

Abstract Individuals whose platelets lack dense core or alpha-granules suffer varying degrees of abnormal bleeding, implying that granule cargo contributes to hemostasis. Despite these clinical observations, little is known regarding the effects of impaired platelet granule secretion on thrombus formation in vivo. The release of cargo from platelet granules requires a group of membrane proteins called SNAREs (Soluble NSF Attachment Protein Receptors) that mediate fusion of granule membranes to the plasma membrane and open canalicular system. Endobrevin/VAMP-8 is the primary vesicular-SNARE (v-SNARE) responsible for efficient release of dense core and a-granule contents. To evaluate the importance of VAMP-8-mediated secretion on the kinetics of thrombus formation in vivo, we measured platelet accumulation following laser-induced vascular injury in VAMP-8−/− mice. Three different phases of thrombus formation - initiation, maximal accumulation, and stabilized platelet accumulation - were tested. Analysis of initial thrombus formation from wild-type and VAMP-8−/− mice showed that average platelet accumulation in VAMP- 8−/− mice was 23% of accumulation in wild-type mice (P=0.009) at 30 sec following injury. There was a trend towards smaller maximal thrombus size in VAMP-8−/− mice, but the difference was not statistically significant (P=0.1). Average stabilized platelet accumulation at 180 sec in VAMP-8−/− mice was 40% of wild-type mice (P=0.05). Thus, thrombus formation is delayed and decreased in VAMP-8−/− mice, but not absent. Dense granule release occurs more rapidly than alpha-granule release, which does not occur for 2–3 min following laser-induced vascular injury. Agonist-induced dense granule release from VAMP-8−/− platelets is defective. To directly evaluate the role of dense granule release on the kinetics of thrombus formation, we assessed thrombus formation in the mouse model of Hermansky-Pudlak syndrome, ruby-eye, which lack dense granules. Thrombus formation following laser-induced vascular injury was nearly abolished in ruby-eye mice such that maximal platelet accumulation was 15% that of wild-type mice. In vitro, the thrombin doses required to induce irreversible aggregation in wild-type, VAMP-8−/−, and ruby-eye platelets were 25 mU, 50 mU, and 150 mU, respectively. Incubation with apyrase had little effect on thrombin-induced aggregation of VAMP-8−/− or ruby-eye platelets. In contrast, incubation of wild-type platelets with apyrase reduced their thrombin sensitivity compared to that of ruby-eye platelets. Supplementation with a substimulatory ADP concentration reversed the thrombin-induced aggregation defect in VAMP-8−/− and ruby-eye mice. Thus, defective ADP release is the primary abnormality leading to impaired aggregation in VAMP-8−/− and ruby-eye mice. Tail bleeding times were assessed in VAMP- 8−/− mice to evaluate the role of VAMP-8 in hemostasis. In contrast to ruby-eye mice, which have a markedly prolonged bleeding time, tail bleeding times in VAMP-8−/− mice were not significantly prolonged compared to those in wild-type mice. These results demonstrate the importance of VAMP-8 and dense granule release in the initial phases of thrombus formation and validate the distal platelet secretory machinery as a potential target for anti-platelet therapies.

scholarly journals Complex molecular genetic diagnostic algorithm in the diagnosis of myeloproliferative neoplasms

2014 ◽  
Vol 155 (52) ◽  
pp. 2074-2081 ◽  
Author(s):  
Tünde Krähling ◽  
Katalin Balassa ◽  
Nóra Meggyesi ◽  
András Bors ◽  
Judit Csomor ◽  
...  
Keyword(s):  
Triple Negative ◽  
Myeloproliferative Neoplasms ◽  
Philadelphia Chromosome ◽  
Molecular Techniques ◽  
Janus Kinase ◽  
Driver Mutations ◽  
Similar Distribution ◽  
Janus Kinase 2 ◽  
Chain Reactions ◽  
Thrombopoietin Receptor

Introduction: Mutations in Janus kinase 2, calreticulin and thrombopoietin receptor genes have been identified in the genetic background of Philadelphia chromosome negative, “classic” myeloproliferative neoplasms. Aim: The aim of the authors was to identify driver mutations in a large myeloproliferative cohort of 949 patients. Method: A complex array of molecular techniques (qualitative and quantitative allele-specific polymerase chain reactions, fragment analyzes, high resolution melting and Sanger sequencing) was applied. Results: All 354 patients with polycythemia vera carried Janus kinase 2 mutations (V617F 98.6%, exon 12: 1.4%). In essential thrombocythemia (n = 468), the frequency of V617F was 61.3% (n = 287), that of calreticulin 25.2% (n = 118), and that of thrombopoietin receptor mutations 2.1% (n = 10), while 11.3% (n = 53) were triple-negative. Similar distribution was observed in primary myelofibrosis (n = 127): 58.3% (n = 74) V617F, 23.6% (n = 30) calreticulin, 6.3% (n = 8) thrombopoietin receptor mutation positive and 11.8% (n = 15) triple-negative. Conclusions: The recent discovery of calreticulin gene mutations led to definite molecular diagnostics in around 90% of clonal myeloproliferative cases. Orv. Hetil., 2014, 155(52), 2074–2081.

High Risk Janus Kinase 2 V617F Allele Burden in a Seven-Year Cohort of Patients with Myeloproliferative Neoplasms

2021 ◽  
Vol 67 (11/2021) ◽  
Author(s):  
Moses Chatambudza ◽  
Lindiwe Skhosana ◽  
Irene Ketseoglou ◽  
Tracey Wiggill
Keyword(s):  
High Risk ◽  
Myeloproliferative Neoplasms ◽  
Janus Kinase ◽  
Janus Kinase 2 ◽  
Allele Burden

Should We Screen for Janus Kinase 2 V617F Mutation in Cerebral Venous Thrombosis?

2017 ◽  
Vol 44 (3-4) ◽  
pp. 97-104 ◽  
Author(s):  
Matthias Lamy ◽  
Paola Palazzo ◽  
Pierre Agius ◽  
Jean Claude Chomel ◽  
Jonathan Ciron ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Cerebral Venous Thrombosis ◽  
Myeloproliferative Neoplasms ◽  
Jak2 V617f ◽  
Janus Kinase ◽  
Jak2 V617f Mutation ◽  
Janus Kinase 2 ◽  
Jak2 Mutation ◽  
Venous Thromboembolic Events ◽  
V617f Mutation

Background: The presence of Janus Kinase 2 (JAK2) V617F mutation represents a major diagnostic criterion for detecting myeloproliferative neoplasms (MPN) and even in the absence of overt MPN, JAK2 V617F mutation is associated with splanchnic vein thrombosis. However, the actual prevalence and diagnostic value of the JAK2 V617F mutation in patients with cerebral venous thrombosis (CVT) are not known. The aims of this study were to assess the prevalence of JAK2 V617F mutation in a large group of consecutive CVT patients, to detect clinical, biological, and radiological features associated with the mutation, and to determine the long-term venous thrombosis recurrence rate in CVT patients with JAK2 mutation but without overt MPN in order to recommend the best preventive treatment. Methods: This was a prospective study conducted on consecutive patients with a first-ever radiologically confirmed CVT. JAK2 V617F mutation analysis was assessed in all the study subjects. JAK2 V617F-positive patients were followed up to detect new venous thrombotic events. Results: Of the 125 included subjects, 7 were found to have JAK2 V617F mutation (5.6%; 95% CI 2.3-11.2). Older age (p = 0.039) and higher platelet count (p = 0.004) were independently associated with JAK2 V617F positivity in patients without overt MPN. During a mean follow-up period of 59 (SD 46) months, 2 JAK2 V617F-positive patients presented with 4 new venous thromboembolic events. Conclusions: Screening for the JAK2 V617F mutation in CVT patients seems to be useful even in the absence of overt MPN and/or in the presence of other risk factors for CVT because of its relatively high prevalence and the risk of thrombosis recurrence.

Role of a Janus kinase 2-dependent signaling pathway in platelet activation

2014 ◽  
Vol 133 (6) ◽  
pp. 1088-1096 ◽  
Author(s):  
Wan-Jung Lu ◽  
Kao-Chang Lin ◽  
Shih-Yi Huang ◽  
Philip Aloysius Thomas ◽  
Yu-Hua Wu ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Platelet Activation ◽  
Janus Kinase ◽  
Janus Kinase 2 ◽  
Dependent Signaling Pathway

Important scaffold function of the Janus kinase 2 uncovered by a novel mouse model harboring a Jak2 activation-loop mutation

Blood ◽  
2014 ◽  
Vol 123 (4) ◽  
pp. 520-529 ◽  
Author(s):  
Eric Keil ◽  
David Finkenstädt ◽  
Christian Wufka ◽  
Mirko Trilling ◽  
Pia Liebfried ◽  
...  
Keyword(s):  
Mouse Model ◽  
Interferon Γ ◽  
Janus Kinase ◽  
Mutant Mice ◽  
Activation Loop ◽  
Janus Kinase 2 ◽  
Key Points

Key Points Jak2 activation-loop–defective mutation results in partial interferon γ signaling, but Jak2 mutant mice die due to abolished EpoR signaling. Jak2 scaffold function mediates IFNGR complex integrity, activity, and physiological Jak1 localization.

Sign in / Sign up

Export Citation Format

Share Document