title: Loss of Ezh2 synergizes with JAK2-V617F in initiating myeloproliferative neoplasms and promoting myelofibrosis.
abstract: Myeloproliferative neoplasm (MPN) patients frequently show co-occurrence of JAK2-V617F and mutations in epigenetic regulator genes, including EZH2 In this study, we show that JAK2-V617F and loss of Ezh2 in hematopoietic cells contribute synergistically to the development of MPN. The MPN phenotype induced by JAK2-V617F was accentuated in JAK2-V617F;Ezh2(-/-) mice, resulting in very high platelet and neutrophil counts, more advanced myelofibrosis, and reduced survival. These mice also displayed expansion of the stem cell and progenitor cell compartments and a shift of differentiation toward megakaryopoiesis at the expense of erythropoiesis. Single cell limiting dilution transplantation with bone marrow from JAK2-V617F;Ezh2(+/-) mice showed increased reconstitution and MPN disease initiation potential compared with JAK2-V617F alone. RNA sequencing in Ezh2-deficient hematopoietic stem cells (HSCs) and megakaryocytic erythroid progenitors identified highly up-regulated genes, including Lin28b and Hmga2, and chromatin immunoprecipitation (ChIP)-quantitative PCR (qPCR) analysis of their promoters revealed decreased H3K27me3 deposition. Forced expression of Hmga2 resulted in increased chimerism and platelet counts in recipients of retrovirally transduced HSCs. JAK2-V617F-expressing mice treated with an Ezh2 inhibitor showed higher platelet counts than vehicle controls. Our data support the proposed tumor suppressor function of EZH2 in patients with MPN and call for caution when considering using Ezh2 inhibitors in MPN.
authors.affiliation: Experimental Hematology, Department of Biomedicine, University Hospital Basel and University of Basel, 4031 Basel, Switzerland.
authors.forename: Takafumi
authors.identifier: 0000-0001-8123-3196
authors.initials: T
authors.lastname: Shimizu
authors.affiliation: Experimental Hematology, Department of Biomedicine, University Hospital Basel and University of Basel, 4031 Basel, Switzerland.
authors.forename: Lucia
authors.identifier: 0000-0002-5605-5006
authors.initials: L
authors.lastname: Kubovcakova
authors.affiliation: Experimental Hematology, Department of Biomedicine, University Hospital Basel and University of Basel, 4031 Basel, Switzerland.
authors.forename: Ronny
authors.initials: R
authors.lastname: Nienhold
authors.affiliation: Experimental Hematology, Department of Biomedicine, University Hospital Basel and University of Basel, 4031 Basel, Switzerland.
authors.forename: Jakub
authors.initials: J
authors.lastname: Zmajkovic
authors.affiliation: Experimental Hematology, Department of Biomedicine, University Hospital Basel and University of Basel, 4031 Basel, Switzerland.
authors.forename: Sara C
authors.identifier: 0000-0002-0308-185X
authors.initials: SC
authors.lastname: Meyer
authors.affiliation: Experimental Hematology, Department of Biomedicine, University Hospital Basel and University of Basel, 4031 Basel, Switzerland.
authors.forename: Hui
authors.initials: H
authors.lastname: Hao-Shen
authors.affiliation: Bioinformatics Core Facility, Department of Biomedicine, University Hospital Basel, 4031 Basel, Switzerland.
authors.forename: Florian
authors.initials: F
authors.lastname: Geier
authors.affiliation: Institute of Pathology, University Hospital Basel, 4031 Basel, Switzerland.
authors.forename: Stephan
authors.initials: S
authors.lastname: Dirnhofer
authors.affiliation: Department of Clinical and Experimental Medicine, University of Florence, 50134 Florence, Italy.
authors.forename: Paola
authors.identifier: 0000-0003-1809-284X
authors.initials: P
authors.lastname: Guglielmelli
authors.affiliation: Department of Clinical and Experimental Medicine, University of Florence, 50134 Florence, Italy.
authors.forename: Alessandro M
authors.identifier: 0000-0001-5755-0730
authors.initials: AM
authors.lastname: Vannucchi
authors.affiliation: CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, 1090 Vienna, Austria.
authors.forename: Jelena D Milosevic
authors.initials: JD
authors.lastname: Feenstra
authors.affiliation: CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, 1090 Vienna, Austria.
authors.forename: Robert
authors.identifier: 0000-0002-6997-8539
authors.initials: R
authors.lastname: Kralovics
authors.affiliation: Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA 02115 Department of Pediatric Oncology, Dana Farber Cancer Institute, Boston, MA 02215 Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02215.
authors.forename: Stuart H
authors.identifier: 0000-0002-3523-7687
authors.initials: SH
authors.lastname: Orkin
authors.affiliation: Experimental Hematology, Department of Biomedicine, University Hospital Basel and University of Basel, 4031 Basel, Switzerland radek.skoda@unibas.ch.
authors.forename: Radek C
authors.initials: RC
authors.lastname: Skoda
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000071221:Enhancer of Zeste Homolog 2 Protein / Q000172:deficiency*; D019337:Hematologic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D053614:Janus Kinase 2 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D020125:Mutation, Missense; D009196:Myeloproliferative Disorders / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D025521:Tumor Suppressor Proteins / Q000172:deficiency*
chemical_list: D025521:Tumor Suppressor Proteins; D000071221:Enhancer of Zeste Homolog 2 Protein; C498410:Ezh2 protein, mouse; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2