The single transmembrane domain (TMD) of the human thrombopoietin receptor (TpoR/MPL), encoded by exon 10 of the MPL gene, is a hotspot for somatic mutations associated with myeloproliferative neoplasms (MPNs).
Studies have shown that mutant calreticulin (CALR) constitutively activates the thrombopoietin (TPO) receptor MPL and thus plays a causal role in the development of myeloproliferative neoplasms (MPNs).
The Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) share similar molecular characteristics in that they frequently harbor hotspot mutations in JAK2, CALR or MPL, leading to activated JAK/STAT signaling.
Sequential genotyping for phenotype-driver mutations in JAK2 (exon 14), CALR (exon 9), and MPL (exon 10) is recommended in patients with myeloproliferative neoplasms.
Studies have previously shown that mutant calreticulin (CALR), found in a subset of patients with myeloproliferative neoplasms (MPNs), interacts with and subsequently promotes the activation of the thrombopoietin receptor (MPL).
Mutations in <i>CALR</i> observed in myeloproliferative neoplasms (MPN) were recently shown to be pathogenic via their interaction with MPL and the subsequent activation of the Janus Kinase - Signal Transducer and Activator of Transcription (JAK-STAT) pathway.
Development of a Targeted Next-Generation Sequencing Assay to Detect Diagnostically Relevant Mutations of JAK2, CALR, and MPL in Myeloproliferative Neoplasms.
We describe here such an association of CALR and MPL mutations in a patient harboring the second mutation in a subclone during the phenotypic evolution of the myeloproliferative neoplasms.
BCR/ABL1-negative myeloproliferative neoplasms (MPNs) are characterized by recurrent mutations in JAK2, CALR, and MPL, each of which has been reported to alter JAK/STAT signaling pathways.
An inhibitor for the thrombopoietin receptor (TpoR) would be more specific for the treatment of myeloproliferative neoplasms (MPNs) due to constitutively active mutant TpoR compared to the current treatment approach of inhibiting Janus kinase 2 (JAK2).
Somatic mutations in JAK2, MPL and CALR are recurrently identified in most of the cases with Philadelphia chromosome negative myeloproliferative neoplasms (MPNs).
The discovery of the activating Janus kinase (JAK)2<sup>V617F</sup> mutation in 2005 in most patients with the classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) spurred intense interest in research into these disorders, culminating in the identification of activating mutations in MPL in 2006 and indels in the gene encoding calreticulin (CALR) in 2013, thus providing additional mechanistic explanations for the universal activation of JAK-signal transducer and activator of transcription (JAK-STAT) observed in these conditions, and the success of the JAK1/2 inhibitor ruxolitinib, which first received regulatory approval in 2011.
JAK2, CALR, MPL and triple-negative mutational status has a direct impact on symptom severity and disease burden assessed by MPN10 score in myeloproliferative neoplasms (MPNs).
The findings from this study support the possibility of coexisting mutations of the JAK2, CALR, and MPL genes in myeloproliferative neoplasms and suggest that CALR and MPL should be analyzed not only in JAK2-negative patients but also in low V617F mutation patients.
The ability to simultaneously detect JAK2 V617F and MPLW515K/L mutations would substantially improve the early diagnosis of myeloproliferative neoplasms (MPNs) and decrease the risk of arterial thrombosis.