Detection of low allele burden of JAK2 exon 12 mutations using TA-cloning in patients with erythrocytosis.

OBJECTIVE Polycythemia vera (PV) is a clonal myeloproliferative neoplasia associated with the activation of the Janus-activating kinase 2 (JAK2) mutation. The aim of this study is to identify clonal expansion of exon 12 mutations. METHODS We performed DNA sequencing of the JAK2 exon 12 after TA-cloning in JAK2-V617F-negative and JAK2-V617F-positive PV patients. RESULTS AND CONCLUSIONS We found clonal mutations (i.e. H538-K539delinsL and D544G) in 3 of 7 JAK2-V617F-negative PV patients, however, unlike JAK2-V617F, allele burden of JAK2 exon 12 mutation was low. Since allele-specific PCR is able to amplify only the limited region which contains known mutations with gain-of-function, we need to clarify the biological implications of unknown single nucleotide substitution of the JAK2 exon 12 with low clonal burden in erythrocytosis patients.