Calreticulin mutations in myeloproliferative neoplasms

Area of Science:

• Molecular Biology
• Hematology
• Oncology

Background:

• The discovery of JAK2V617F mutation advanced myeloproliferative neoplasms (MPNs) understanding and therapy.
• A significant portion of essential thrombocythemia (ET) and primary myelofibrosis (PMF) patients lacked known mutations (JAK2, MPL).

Purpose of the Study:

• To identify mutations in ET and PMF patients negative for JAK2 or MPL mutations.
• To elucidate the role of calreticulin (CALR) mutations in Philadelphia chromosome-negative (Ph(-)) MPNs.

Main Methods:

• Whole-exome sequencing was employed to identify recurrent mutations.
• Analysis focused on exon 9 of the CALR gene, specifically deletions and insertions.

Main Results:

• Recurrent CALR mutations (type 1 and type 2) were identified in the majority of JAK2/MPL-negative ET and PMF patients.
• These mutations lead to frameshift changes, producing a novel C-terminal amino acid sequence in calreticulin.
• CALR mutations were found to activate JAK/STAT signaling and occur early in disease development.

Conclusions:

• CALR mutations are the second most frequent genetic drivers in Ph(-) MPNs after JAK2V617F.
• Detection of CALR mutations significantly enhances diagnostic accuracy for ET and PMF.
• CALR mutations have critical diagnostic, clinical, and pathogenetic implications for MPNs.