Improved Diagnosis of the Transition to JAK2 (V617F) Homozygosity: The Key Feature for Predicting the Evolution of Myeloproliferative Neoplasms

Most cases of BCR-ABL1-negative myeloproliferative neoplasms (MPNs), essential thrombocythemia, polycythemia vera and primary myelofibrosis are associated with JAK2 (V617F) mutations. The outcomes of these cases are critically influenced by the transition from JAK2 (V617F) heterozygosity to homozygosity. Therefore, a technique providing an unbiased assessment of the critical allele burden, 50% JAK2 (V617F), is highly desirable. In this study, we present an approach to assess the JAK2 (V617F) burden from genomic DNA (gDNA) and complementary DNA (cDNA) using one-plus-one template references for allele-specific quantitative-real-time-PCR (qPCR). Plasmidic gDNA and cDNA constructs encompassing one PCR template for JAK2 (V617F) spaced from one template for JAK2(Wild Type) were constructed by multiple fusion PCR amplifications. Repeated assessments of the 50% JAK2(V617F) burden within the dynamic range of serial dilutions of gDNA and cDNA constructs resulted in 52.53±4.2% and 51.46±4.21%, respectively. The mutation-positive cutoff was estimated to be 3.65% (mean +2 standard deviation) using 20 samples from a healthy population. This qPCR approach was compared with the qualitative ARMS-PCR technique and with two standard methods based on qPCR, and highly significant correlations were obtained in all cases. qPCR assays were performed on paired gDNA/cDNA samples from 20 MPN patients, and the JAK2 (V617F) expression showed a significant correlation with the allele burden. Our data demonstrate that the qPCR method using one-plus-one template references provides an improved assessment of the clinically relevant transition of JAK2 (V617F) from heterozygosity to homozygosity.