The Investigation of JAK2 and C-MPL Mutations of Myeloproliferative Disorders Patiens

Most studies have shown that JAK2V617F was found in nearly all the patients with polycythemia vera (PV) and half of patients with essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF). However, JAK2 exon 12 mutations in JAK2V61F-negetive PV patiens and MPLW515L/K mutations in IMF patiens implied other pathogenesis in these myeloproliferative disorders (MPD). Two parts were included in our research to investigate the JAK2 and c-MPL mutations of MPD patients. Firstly, to evaluate the JAK2 exon 12 mutations and its clinical significance in patients with PV, polymerase chain reaction was used to amply the region of JAK2 exon 12 and direct sequencing was performed to detect mutations of JAK2 exon 12. Clinical features of the PV patients with JAK2 exon 12 mutations and JAK2V617F mutation were retrospectively reviewed. The results showed that the JAK2 exon 12 mutations were detected in 3 of 12 JAK2V617F-negtive PV patients (25.0%). Three JAK2 exon 12 mutations were H538QK539L, K539L and N542-E543del respectively. The patients carrying the mutations of JAK2 exon 12 displayed higher hemoglobin(223.6±15.0 vs190.3±20.2g/l, P<0.05), lower white blood cell counts (7.8±2.3 vs16.2±6.7 *10⁹/l, P<0.05)compared with JAK2V617F-positive PV patients (n=31). Secondly, allele specific polymerase chain reaction (AS-PCR) and gene sequencing were used to detected JAK2V617F, MPLW515L and four types of JAK2 exon 12 mutations (F537-K539delinsL, H538QK539L, K539L, N542-E543del) in 30 IMF patients. Results showed that 15 of 30 (50.0%) patients had JAK2V617F mutation and 2 of 30 (6.7%) patients had MPLW515L mutation. JAK2 exon 12 mutations were not detected in IMF patients. Literature reviews show that this is the first report of JAK2 and c-MPL mutations in a number of Chinese patients with BCR/ABL-negative MPD. It is concluded that the JAK2 exon 12 mutations exist in PV patient and the patients with JAK2 exon 12 mutations are characterized by isolated erythrocytosis. The frequency of MPLW515L mutations is high in IMF, which supports recent studies.