JAK2 mutation and disease phenotype: a double L611V/V617F in cis mutation of JAK2 is associated with isolated erythrocytosis and increased activation of AKT and ERK1/2 rather than STAT5

Anti-inflammatory cytokines hepatocyte growth factor and interleukin-11 are over-expressed in Polycythemia vera and contribute to the growth of clonal erythroblasts independently of JAK2V617F

“…In comparison, the increase in tyrosine phosphorylation of STAT5 and STAT3 in BaF-3/Epo-R cells expressing JAK2V617F was modest. Expression in BaF-3/Epo-R cells of wildtype and V617F-mutated JAK2, as well as another JAK2 mutant, JAK2L611V/V617F (Cleyrat et al, 2010), had no effect on mRNA expression of murine IL-11 or HGF, the latter remaining below detection level (Figure 5b). However, all forms of JAK2 induced a moderate increase in mRNA and protein levels of murine IL-6.…”

“…For cell signalling studies, transfected BaF-3/Epo-R cells were washed, deprived of Epo for 5 h in RPMI medium supplemented with 10% FCS, then stimulated for 10 min with Epo (25 IU/ml) in RPMI and 2% FCS, at 37 1C. Cells were harvested, washed twice in cold PBS, lysed in 60 ml RIPA buffer, then proteins (25 mg) were loaded on 10% SDS-PAGE and transferred to polyvinylidene fluoride membranes (Millipore Corporation, Billerica, MA, USA) (Corre-Buscail et al, 2005;Cleyrat et al, 2010). After blocking with 5% non-fat dry milk, membranes were incubated with Abs specific for p-STAT5 (Zymed, San Francisco, CA, USA), p-JAK2 and p-STAT3 (Cell Signalling, Danvers, MA, USA) or b-actin (Millipore Corporation), then stripped and re-probed with Ab specific for total JAK2 (Millipore Corporation), STAT3 and STAT5 (BD Bioscience, San Jose, CA, USA).…”

“…Yet, in murine models, JAK2V617F is associated with polycythemia only when expressed at high levels (450% JAK2V617F-mutated alleles), whereas a significant proportion of PV patients carry o50% JAK2V617F (Lacout et al, 2006;Lippert et al, 2006;Wernig et al, 2006;Tiedt et al, 2008). We now know that the JAK2V617F mutation is frequently associated with other molecular genetic abnormalities and that the JAK2V617F mutation can occur several times in certain patients; moreover, the presence of JAK2V617F does not ensure expansion of mutated progenitors (Nussenzveig et al, 2007;Kralovics, 2008;Lambert et al, 2009;Schaub et al, 2009;Cleyrat et al, 2010). Hence, the role of JAK2V617F in MPN and the consequences of its expression in hematopoietic progenitors remain incompletely understood.…”

The JAK2 46/1 haplotype: a marker of inappropriate myelomonocytic response to cytokine stimulation, leading to increased risk of inflammation, myeloid neoplasm, and impaired defense against infection?

“…Activating mutations in these exons are likely to be detected as they confer growth advantages to the mutated clone, whereas silent mutations typically remain below the detection level of most diagnostic assays. 13 DNA repeat elements include GC-or AT-rich sequences; they can be mutation "hot spots", cause mismatching during DNA replication, or form fragile chromosomal break The "GGCC" part, which begins in intron 10 and finishes in intron 15 of the JAK2 gene, is characterized by four single nucleotide polymorphisms: rs3780367 in intron 10, rs10974944 in intron 12, rs12343867 in intron 14, and rs1159782 in intron 15. These four single nucleotide polymorphisms are in complete linkage disequilibrium.…”

Chasing down the triple-negative myeloproliferative neoplasms: Implications for molecular diagnostics

“…Rare, alternative, somatic mutations in both JAK2 exon 14 and MPL exon 10, often at the same codon as the more common mutations, have been previously noted but may account for only a minority of triple-negative MPN. [5][6][7][8][9] In order to address this issue, several groups have recently applied either whole exome sequencing and/or targeted exon sequencing to triple negative MPN, particularly ET cases, and which have informed further understanding of the molecular pathogenesis of this group of patients. [10][11][12] In addition to sporadic mutations in epigenetic modifying (ASXL1, TET2), spliceosome (SF3B1, SRSF2), and regulators of cytokine signaling (CBL, SH2B3) genes, a significant number of mutations were detected in both the JAK2 and MPL genes, strikingly in exons not normally mutated in MPN (Fig.…”