Low-Level Expression of a JAK2 Splice Variant with Exon 14 Deletion Is Common in Patients with Chronic Myeloproliferative Neoplasms
Z Zhang, W Ma, TS Lee, X Zhang, X Wang, CH Yeh, M Albitar. Quest Diagnostics Nichols Institute, San Juan Capistrano, CA; University of Minnesota, Minneapolis, MN
Background: We previously reported detection of a JAK2 splice variant transcript with complete deletion of exon 14 (88 bp, encompassing V617; 14-del) in rare patients with chronic myeloproliferative neoplasms (MPNs). Molecular modeling simulations suggested that 14-del will exhibit dominant-negative effects leading to constitutive activation of the JAK2-STAT pathway, similar to that caused by V617F mutation. Although 14-del was detected at levels >15% of total JAK2 transcript (detection limit of original assay) in the previously reported cases, we speculate that some patients may express low levels of this splice variant.
Design: To determine the frequency of low-level expression, we designed a highly sensitive reverse-transcription/polymerase chain reaction (RT/PCR) test to quantify abnormally spliced 14-del transcript at levels as low as 1% of total JAK2 transcript. This assay was used to test samples from 61 patients with confirmed MPN, 183 patients with suspected MPN, and 46 healthy normal controls.
Results: The 14-del transcript was found at low levels (2.1% to 33.9% of wild-type levels) in 60 patients: 9 (15%) with confirmed MPN, 51 (28%) with suspected MPN, and none in normal controls. Roughly one-third of V617F-negative samples (31/90) from patients with MPN or suspected MPN were positive for 14-del expression. In twenty cases (20/93), the 14-del transcript coexisted with V617F transcript.
Conclusions: Although more functional data are needed, our findings suggest that the expression of this abnormally spliced JAK2 transcript may be a common molecular abnormality in MPN, one that may cause constitutive activation of the JAK2-STAT pathway and thus contribute to the neoplastic phenotype in MPNs.
Tuesday, March 23, 2010 8:00 AM
Platform Session: Section B, Tuesday Morning