Calreticulin mutant mice develop essential thrombocythemia that is ameliorated by the JAK inhibitor ruxolitinib.
Mutations of calreticulin (CALR) are detected in 25-30% of patients with essential thrombocythemia (ET) or primary myelofibrosis and cause frameshifts that result in proteins with a novel C-terminal. We demonstrate that CALR mutations activated signal transducer and activator of transcription 5 (STAT5) in 293T cells in the presence of thrombopoietin receptor (MPL). Human megakaryocytic CMK11-5 cells and erythroleukemic F-36P-MPL cells with knocked-in CALR mutations showed increased growth and acquisition of cytokine-independent growth, respectively, accompanied by STAT5 phosphorylation. Transgenic mice expressing a human CALR mutation with a 52 bp deletion (CALRdel52-transgenic mice (TG)) developed ET, with an increase in platelet count, but not hemoglobin level or white blood cell count, in association with an increase in bone marrow (BM) mature megakaryocytes. CALRdel52 BM cells did not drive away wild-type (WT) BM cells in in vivo competitive serial transplantation assays, suggesting that the self-renewal capacity of CALRdel52 hematopoietic stem cells (HSCs) was comparable to that of WT HSCs. Therapy with the Janus kinase (JAK) inhibitor ruxolitinib ameliorated the thrombocytosis in TG mice and attenuated the increase in number of BM megakaryocytes and HSCs. Taken together, our study provides a model showing that the C-terminal of mutant CALR activated JAK-STAT signaling specifically downstream of MPL and may have a central role in CALR-induced myeloproliferative neoplasms.
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Shide
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Kameda
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Yamaji
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Sekine
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Inada
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Kamiunten
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Akizuki
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Nakamura
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Hidaka
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Kubuki
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Shimoda
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Kitanaka
Organization for Promotion of Tenure Track, University of Miyazaki, Miyazaki, Japan.
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Honda
Faculty of Medicine, Ultrastructural Cell Biology, Department of Anatomy, University of Miyazaki, Miyazaki, Japan.
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Sawaguchi
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Abe
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Miike
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Iwakiri
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Tahara
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Sueta
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Hasuike
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Yamamoto
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Nagata
Faculty of Medicine, Department of Gastroenterology and Hematology, University of Miyazaki, Miyazaki, Japan.
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Shimoda
D000818:Animals; D037282:Calreticulin / Q000235:genetics*; D000066673:Cell Self Renewal; D057809:HEK293 Cells; D006412:Hematopoietic Stem Cells; D006801:Humans; D053612:Janus Kinases / Q000037:antagonists & inhibitors; D051379:Mice; D008822:Mice, Transgenic; D009196:Myeloproliferative Disorders / Q000139:chemically induced / Q000209:etiology; D009570:Nitriles; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D011720:Pyrazoles / Q000494:pharmacology / Q000627:therapeutic use; D011743:Pyrimidines; D053628:Receptors, Thrombopoietin; D050799:STAT5 Transcription Factor / Q000378:metabolism; D013920:Thrombocythemia, Essential / Q000188:drug therapy / Q000235:genetics
D037282:Calreticulin; D009570:Nitriles; D047428:Protein Kinase Inhibitors; D011720:Pyrazoles; D011743:Pyrimidines; D053628:Receptors, Thrombopoietin; D050799:STAT5 Transcription Factor; C540383:ruxolitinib; D053612:Janus Kinases