Calreticulin mutants in mice induce an MPL-dependent thrombocytosis with frequent progression to myelofibrosis
Calreticulin mutants in mice induce an MPL-dependent thrombocytosis with frequent progression to myelofibrosis
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DOI：
10.1182/blood-2015-11-679571
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发表时间：
2016-03-10
期刊：
影响因子：
20.3
通讯作者：
Vainchenker, William
中科院分区：
文献类型：
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作者：
Marty, Caroline;Pecquet, Christian;Vainchenker, William
钙网蛋白 (CALR) 基因移码突变见于约 30% 的原发性血小板增多症和骨髓纤维化患者。为了解决 CALR 突变体对骨髓增殖性肿瘤发病机制的影响，我们将用表达这些突变体的逆转录病毒转导的骨髓细胞移植到经过致死照射的受体小鼠中。与野生型 CALR 相比，CALRdel52（I 型）以及较小程度上的 CALRins5（II 型）由于巨核细胞 (MK) 增生而诱导血小板增多。疾病可以移植到第二受体中。 6 个月后，与罕见的 CALRins5- 相比，CALRdel52- 转导小鼠出现了与脾肿大相关的骨髓纤维化和明显的骨硬化。对病毒转导群体的监测表明，CALRdel52 比 CALRins5 导致造血早期阶段的扩增。然而，两种突变体仍然特异性扩增 MK 谱系和血小板产生。此外，删除整个外显子 9 的突变体 (CALRdelex9) 不会诱发疾病，这表明 CALR 突变体的致癌特性与新的 C 末端肽有关。为了了解 CALR 突变体如何靶向 MK 谱系，我们使用细胞系模型并证明 CALR 突变体（而非 CALRdelex9）特异性激活血小板生成素 (TPO) 受体 (MPL)，以诱导 Janus 激酶 2 和信号转导器以及转录 5/3/1 激活剂的组成型激活。我们在 c-mpl 和 tpo 缺陷小鼠中证实，尽管 Tpo 有助于疾病外显，但 Mpl 的表达（而非 Tpo）对于 CALR 突变体诱导体内血小板增多至关重要。因此，CALR 突变体足以通过 MPL 激活诱导血小板增多。
Frameshift mutations in the calreticulin (CALR) gene are seen in about 30% of essential thrombocythemia and myelofibrosis patients. To address the contribution of the CALR mutants to the pathogenesis of myeloproliferative neoplasms, we engrafted lethally irradiated recipient mice with bone marrow cells transduced with retroviruses expressing these mutants. In contrast to wild-type CALR, CALRdel52 (type I) and, to a lesser extent, CALRins5 (type II) induced thrombocytosis due to a megakaryocyte (MK) hyperplasia. Disease was transplantable into secondary recipients. After 6 months, CALRdel52-, in contrast to rare CALRins5-, transduced mice developed a myelofibrosis associated with a splenomegaly and a marked osteosclerosis. Monitoring of virus-transduced populations indicated that CALRdel52 leads to expansion at earlier stages of hematopoiesis than CALRins5. However, both mutants still specifically amplified the MK lineage and platelet production. Moreover, a mutant deleted of the entire exon 9 (CALRdelex9) did not induce a disease, suggesting that the oncogenic property of CALR mutants was related to the new C-terminus peptide. To understand how the CALR mutants target the MK lineage, we used a cell-line model and demonstrated that the CALR mutants, but not CALRdelex9, specifically activate the thrombopoietin (TPO) receptor (MPL) to induce constitutive activation of Janus kinase 2 and signal transducer and activator of transcription 5/3/1. We confirmed in c-mpl- and tpo-deficient mice that expression of Mpl, but not of Tpo, was essential for the CALR mutants to induce thrombocytosis in vivo, although Tpo contributes to disease penetrance. Thus, CALR mutants are sufficient to induce thrombocytosis through MPL activation.