Homozygous calreticulin mutations in patients with myelofibrosis lead to acquired myeloperoxidase deficiency

Theocharides, A. P. and Lundberg, P. and Lakkaraju, A. K. and Lysenko, V. and Myburgh, R. and Aguzzi, A. and Skoda, R. C. and Manz, M. G.. (2016) Homozygous calreticulin mutations in patients with myelofibrosis lead to acquired myeloperoxidase deficiency. Blood, 127 (25). pp. 3253-3259.

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Official URL: https://edoc.unibas.ch/62461/

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The pathogenesis of acquired myeloperoxidase (MPO) deficiency, a rare phenomenon observed in patients with Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), is unknown. MPO is a glycoprotein (GP) chaperoned by calreticulin (CALR) in the endoplasmic reticulum. Mutations in CALR are frequently found in patients with myelofibrosis (MF) and essential thrombocythemia (ET) with nonmutated Janus kinase 2 (JAK2). We hypothesized that acquired MPO deficiency in MPN could be associated with the presence of CALR mutations. A cohort of 317 patients with MPN (142 polycythemia vera [PV], 94 ET, and 81 MF) was screened for MPO deficiency. MPO deficiency was observed in 6/81 MF patients (7.4%), but not in PV or ET patients. Susceptibility to infections had been documented in 2/6 (33%) MPO-deficient patients. Five out of 6 patients with MPO deficiency carried a homozygous CALR mutation and were also deficient in eosinophilic peroxidase (EPX). In contrast, 1 patient with MF, a JAK2-V617F mutation, and MPO deficiency, carried 2 previously reported MPO mutations and showed normal EPX activity. Patients with homozygous CALR mutations had reduced MPO protein, but normal MPO messenger RNA (mRNA) levels supporting a posttranscriptional defect in MPO production. Finally, we demonstrate in vitro that in the absence of CALR, immature MPO protein precursors are degraded in the proteasome. Therefore, 4 decades after the first description of acquired MPO deficiency in MPN, we provide the molecular correlate associated with this phenomenon and evidence that CALR mutations can affect the biosynthesis of GPs.
Faculties and Departments:03 Faculty of Medicine > Departement Biomedizin > Department of Biomedicine, University Hospital Basel > Experimental Hematology (Skoda)
UniBasel Contributors:Skoda, Radek C.
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:11 Dec 2018 17:19
Deposited On:11 Dec 2018 17:19

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