文章：

携带与人类CALR突变同源的Calr突变的小鼠仅表现出轻度血小板增多症

Mice with Calr mutations homologous to human CALR mutations only exhibit mild thrombocytosis

原文发布日期：2019-03-29

DOI: 10.1038/s41408-019-0202-z

类型: Article

开放获取: 是

英文摘要：

Calreticulin (CALR) exon 9 frameshift mutations, commonly detected in essential thrombocythemia (ET) and primary myelofibrosis patients, activate signal transducer and activator of transcription (STAT) proteins in the presence of Myeloproliferative Leukemia Virus (MPL) and induce ET in vivo. Loss of the KDEL motif, an endoplasmic reticulum retention signal, and generation of many positively charged amino acids (AAs) in the mutated C-terminus are thought to be important for disease induction. To test this hypothesis, we generated mice harboring a Calr frameshift mutation using the CRISPR/Cas9 system. Deletion of 19-base pairs in exon 9 (c.1099-1117del), designated the del19 mutation, induced loss of the KDEL motif and generated many positively charged AAs, similar to human mutants. Calr del19 mice exhibited mild thrombocytosis, slightly increased megakaryocytes, and mild splenomegaly. In vitro experiments revealed that the murine CALR del19 mutant had a weaker ability to combine with murine MPL than the human CALR del52 mutant. Consequently, STAT5 activation was also very weak downstream of the murine mutant and murine MPL, and may be the reason for the mild disease severity. In summary, loss of the KDEL motif and positively charged AAs in the C-terminus of CALR is insufficient for MPL binding and ET development.
 

摘要翻译： 

钙网蛋白（CALR）第9外显子移码突变常见于原发性血小板增多症（ET）和原发性骨髓纤维化患者，该突变在骨髓增殖性白血病病毒（MPL）存在时会激活信号转导与转录激活因子（STAT）蛋白，并在体内诱导ET发生。内质网滞留信号KDEL基序的缺失以及突变C末端产生大量带正电荷氨基酸，被认为在疾病诱导中起关键作用。为验证这一假说，我们利用CRISPR/Cas9系统构建了携带Calr移码突变的小鼠模型。第9外显子19个碱基对的缺失（c.1099-1117del）被命名为del19突变，该突变导致KDEL基序缺失并产生大量带正电荷氨基酸，与人类突变特征相似。Calr del19小鼠表现为轻度血小板增多、巨核细胞轻度增生及脾脏轻度肿大。体外实验显示，小鼠CALR del19突变体与小鼠MPL的结合能力弱于人源CALR del52突变体。因此，在小鼠突变体与小鼠MPL的下游信号通路中，STAT5的激活程度也非常微弱，这可能是疾病严重程度较轻的原因。总之，CALR蛋白C末端KDEL基序缺失和带正电荷氨基酸的产生，并不足以实现MPL结合及诱发ET。

原文链接：

Mice with Calr mutations homologous to human CALR mutations only exhibit mild thrombocytosis