Three‐way translocation (X;20;16)(p11;q13;q23) in essential thrombocythemia implicates NFATC2 in dysregulation of CSF2 expression and megakaryocyte proliferation

Abstract

Essential thrombocythemia (ET) is a myeloproliferative neoplasm essentially characterized by excessive production of platelets. Molecular pathogenesis of ET is linked in approximately half of the patients to intracellular cytokine signaling dysregulation as a result of thrombopoietin receptor or Janus kinase 2 (JAK2) mutations. However, genetic defects underlying cytokine transcription have not been associated with ET. Using molecular cytogenetics and whole-genome array analyses, we uncovered a submicroscopic deletion at 20q13.2 in a JAK2V617F-positive ET patient with an acquired complex chromosome translocation. The deletion encompassed the nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 2 (NFATC2) gene that encodes a transcription factor involved in the regulation of hematopoietic cytokines. RNA interference-mediated suppression of NFATC2 mRNA or pharmacological inhibition of NFATC2 protein with 11R-VIVIT in cultured JAK2V617F-positive SET-2 megakaryocytes increased colony stimulating factor 2 (granulocyte-macrophage) (CSF2) mRNA and promoted cell proliferation. Moreover, impairment of NFATC2-calcineurin interaction with 11R-VIVIT further reduced the transcription of the NFATC2 gene. Antibody-mediated neutralization of CSF2 cytokine in inhibitor-treated cells prevented 11R-VIVIT-induced cell proliferation, indicating that impairment of NFATC2-calcineurin interaction promotes megakaryocyte proliferation through up-regulation of CSF2 transcription. Our results suggest a model in which haplo-insufficiency of NFATC2 cooperates with activation of the JAK-STAT signaling pathway in the pathogenesis of JAK2V617F-positive ET with del(20q). These results further indicate that pathogenesis of ET may be linked to genetic defects of other transcription factor genes involved in the regulation of cytokine expression.

Transcriptional Regulation of Platelet Formation: Harnessing the Complexity for Efficient Platelet Production In Vitro

“…FKBP5, another calcineurin inhibitor, was found to be upregulated in myelofibrosis [177]. Furthermore, in one patient with essential thrombocythaemia, a three-way translocation which created a breakpoint in NFATC2 was identified possibly contributing to the overproliferation of MKs [178].…”

Integrative Genomic and Transcriptomic Analysis Identified Candidate Genes Implicated in the Pathogenesis of Hepatosplenic T-Cell Lymphoma

“…NFATC2 also controls the cell-cycle progression by repressing expression of the G0–G1 checkpoint kinase CDK4 and cyclins A2, BA, E and F [75]–[77], and induces apoptosis in NIH3T3 fibroblasts in cooperation with the Ras/Raf/MEK/ERK pathway [63]. Recently, it was reported that haploinsufficency of NFATC2 contributes to the pathogenesis of essential thrombocythemia with del(20q) [78]. In this context, particularly interesting is the study of Caloca et al .…”

Myeloproliferative Syndromes and Thrombocythemia

“…Forty to fifty percent of the patients carry the Janus kinase 2 (JAK2) V617F or a functionally similar mutation, but these mutations are not specific for ET, because they are found in polycythemia vera and primary myelofibrosis as well (Cho et al 2009;Deepak et al 2011;Kiladjian 2012;Martinez-Avilez et al 2012;Pich et al 2012). One percent of ET patients show a gain of function mutation of MPL, MPL W515K/ L. In patients with JAK2 V617F-positive ET with del(20q), haploinsufficiency of the nuclear factor of activated T-cells, cytoplasmic, calcineurindependent 2/NFATC2 seems to cooperate with activation of the JAK-STAT signaling pathway (Vieira et al 2012). Mutations of TET2 (tet oncogene family member 2) were detected in both JAK-positive and JAK-negative ET, but only in a minority of cases and more often in older patients (Tefferi et al 2009;Martinez-Aviles et al 2012).…”