Abstract
JAK2V617F is the predominant mutation in myeloproliferative neoplasms (MPN). Modeling MPN in a human context might be helpful for the screening of molecules targeting JAK2 and its intracellular signaling. We describe here the derivation of induced pluripotent stem (iPS) cell lines from 2 polycythemia vera patients carrying a heterozygous and a homozygous mutated JAK2V617F, respectively. In the patient with homozygous JAK2V617F, additional ASXL1 mutation and chromosome 20 allowed partial delineation of the clonal architecture and assignation of the cellular origin of the derived iPS cell lines. The marked difference in the response to erythropoietin (EPO) between homozygous and heterozygous cell lines correlated with the constitutive activation level of signaling pathways. Strikingly, heterozygous iPS cells showed thrombopoietin (TPO)-independent formation of megakaryocytic colonies, but not EPO-independent erythroid colony formation. JAK2, PI3K and HSP90 inhibitors were able to block spontaneous and EPO-induced growth of erythroid colonies from GPA+CD41+ cells derived from iPS cells. Altogether, this study brings the proof of concept that iPS can be used for studying MPN pathogenesis, clonal architecture, and drug efficacy.
Highlights
An important breakthrough in the understanding of BCRABL–negative myeloproliferative neoplasms (MPN) has been accomplished by the discovery of the JAK2V617F mutation, underlying the role of pathologic JAK/STAT signaling in MPN [1,2]
Around 60% of CD34+ cells from patient 2 [P2(h)] exhibited a heterozygous JAK2V617F mutation (JAK2V617F/WT) whereas no mutation was identified in these cells in ASXL1 and the other genes involved in myeloid malignancies, including TET2, EZH2, DNMT3A, IDH1 and SRSF2 [6]
We evaluated by qRT-PCR the expression levels of globin transcripts in erythroblasts derived from patient 1, patient 2 and the control Induced pluripotent stem cells (iPS) cell lines in comparison with erythroblasts derived from ES and adult cells
Summary
An important breakthrough in the understanding of BCRABL–negative MPN has been accomplished by the discovery of the JAK2V617F mutation, underlying the role of pathologic JAK/STAT signaling in MPN [1,2]. Most patients with JAK2V617F ET harbor only one mutated allele (heterozygous), whereas most of those with JAK2V617F PV harbor two mutated alleles (homozygous), supporting the hypothesis that phenotypic heterogeneity of JAK2V617F-induced diseases might be due to the level of JAK2 signaling [3,4]. Other recurrent mutations have been found in genes involved in epigenetic regulation and/or in RNA splicing [5,6]. These mutations, which can be either pre-JAK2V617F or post-JAK2V617F events, may be involved in clonal dominance, as for TET2 and DNMT3A mutations, or in disease progression as is the case for ASXL1, SRSF2 or IDH1 mutations [5,6]. IPS were successfully generated from acquired malignant disorders such as chronic myeloid leukemia (CML) and non-CML MPN [8,9]
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