title: JAK2 exon 14 deletion in patients with chronic myeloproliferative neoplasms.
abstract: BACKGROUND
  The JAK2 V617F mutation in exon 14 is the most common mutation in chronic myeloproliferative neoplasms (MPNs); deletion of the entire exon 14 is rarely detected. In our previous study of >10,000 samples from patients with suspected MPNs tested for JAK2 mutations by reverse transcription-PCR (RT-PCR) with direct sequencing, complete deletion of exon 14 (Deltaexon14) constituted <1% of JAK2 mutations. This appears to be an alternative splicing mutation, not detectable with DNA-based testing.
  
  
  RESULTS
  We investigated the possibility that MPN patients may express the JAK2 Deltaexon14 at low levels (<15% of total transcript) not routinely detectable by RT-PCR with direct sequencing. Using a sensitive RT-PCR-based fluorescent fragment analysis method to quantify JAK2 Deltaexon14 mRNA expression relative to wild-type, we tested 61 patients with confirmed MPNs, 183 with suspected MPNs (93 V617F-positive, 90 V617F-negative), and 46 healthy control subjects. The Deltaexon14 variant was detected in 9 of the 61 (15%) confirmed MPN patients, accounting for 3.96% to 33.85% (mean = 12.04%) of total JAK2 transcript. This variant was also detected in 51 of the 183 patients with suspected MPNs (27%), including 20 of the 93 (22%) with V617F (mean [range] expression = 5.41% [2.13%-26.22%]) and 31 of the 90 (34%) without V617F (mean [range] expression = 3.88% [2.08%-12.22%]). Immunoprecipitation studies demonstrated that patients expressing Deltaexon14 mRNA expressed a corresponding truncated JAK2 protein. The Deltaexon14 variant was not detected in the 46 control subjects.
  
  
  CONCLUSIONS
  These data suggest that expression of the JAK2 Deltaexon14 splice variant, leading to a truncated JAK2 protein, is common in patients with MPNs. This alternatively spliced transcript appears to be more frequent in MPN patients without V617F mutation, in whom it might contribute to leukemogenesis. This mutation is missed if DNA rather than RNA is used for testing.
authors: Department of Hematology/Oncology, Quest Diagnostics Nichols Institute, San Juan Capistrano, California, USA.
authors: Wanlong
authors: W
authors: Ma
authors: Hagop
authors: H
authors: Kantarjian
authors: Xi
authors: X
authors: Zhang
authors: Xiuqiang
authors: X
authors: Wang
authors: Zhong
authors: Z
authors: Zhang
authors: Chen-Hsiung
authors: CH
authors: Yeh
authors: Susan
authors: S
authors: O'Brien
authors: Francis
authors: F
authors: Giles
authors: Jean Marie
authors: JM
authors: Bruey
authors: Maher
authors: M
authors: Albitar
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D019046:Bone Marrow Neoplasms / Q000235:genetics*; D002908:Chronic Disease; D005091:Exons / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053614:Janus Kinase 2 / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009196:Myeloproliferative Disorders / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion
chemical_list: D012333:RNA, Messenger; D053614:Janus Kinase 2