Detection ofJAK2mutations in paraffin marrow biopsies by high resolution melting analysis: identification ofL611Salone and in cis withV617Fin polycythemia vera

Case report: Double L611S/V617L JAK2 mutation in a patient with polycythemia vera originally diagnosed with essential thrombocythemia

Double JAK2 mutations have rarely been described in myeloproliferative neoplasms (MPNs) and are demonstrated to be associated with the polycythemia vera (PV) phenotype. Here, we first report a case of a PV patient with a de novo double L611S/V617L in cis mutation of JAK2. A 40-year-old woman was admitted to the hospital with massive splenomegaly, multiple splenic infarcts, and abdominal pain. She had a 4-year history of erythrocytosis with an antecedent 10-year history of thrombocytosis before coming to our hospital. She was diagnosed with JAK2 L611S/V617L double-mutant PV after a detailed medical examination in 2017. According to the literature, IFNα therapy can induce clinical, hematological, histopathological, and occasionally molecular remission in individuals with MPNs. Our report demonstrates that combination therapy with ruxolitinib and IFNα can lead to a substantial reduction in JAK2 L611S/V617L double-mutant allele burden.

Validating the Sensitivity of High-Resolution Melting Analysis for JAK2 V617F Mutation in the Clinical Setting

BACKGROUND

Janus kinase 2 (JAK2) plays an important role in normal hematopoietic growth factor signaling. The detection of the JAK2 V617F mutation (c.1849GNT, GTC → TTC) is crucial for the diagnosis of myeloproliferative neoplasm (MPN) and has become the essential criteria for diagnosis of MPN by the WHO. High-resolution melt (HRM) curve analysis is a nongel-based, closed-tube method, in which PCR amplification and subsequent analysis are sequentially performed in the well, making it more convenient than other scanning methodologies.

METHODS

We evaluated JAK2 V617F mutation by HRM. Twenty-nine patients diagnosed with MPN were examined. We studied the analytical sensitivity of the HRM analysis using real-time polymerase chain reaction (PCR) for identifying the JAK2 V617F mutation. Additionally, the sensitivity of HRM analysis and allele-specific PCR (AS-PCR) assay was compared.

RESULTS

The JAK2 V617F mutation was successfully discriminated at an abundance of 6% or above in HRM analysis. Both HRM analysis and AS-PCR showed 100% accuracy with detection limits of 6% and 2.5%, respectively.

CONCLUSION

HRM analysis is a fast, simple, reliable, and nonexpensive method for the detection of the JAK2 V617F mutation. However, more validation of the detection limits of HRM analysis should be performed before declaration of the analytic sensitivity of the method.

Deparaffinization with mineral oil: a simple procedure for extraction of high-quality DNA from archival formalin-fixed paraffin-embedded samples

Extracting DNA from formalin-fixed paraffin-embedded (FFPE) archival samples remains difficult. Successful polymerase chain reactions (PCR) with DNA extracted from FFPE samples is still very low. We extracted DNA from 12 recent and old archival FFPE bone marrow trephine biopsies by use of a simple protocol on the basis of deparaffinization with molecular biology-grade mineral oil followed by DNA extraction with the Qiagen FFPE kit. Comparison of this deparaffinization method with standard protocols, for example, xylene or Hemo-D with subsequent rehydration using graded ethanols, was investigated. The quality and quantity of extracted DNA were tested by a combination of ultraviolet spectroscopy, analysis on a Caliper LabChip GX, and real-time PCR combined with high-resolution melt analysis. Highest quality PCR-amplifiable DNA was obtained by deparaffinization with mineral oil, whereas more variable results were obtained for the other 2 deparaffinization procedures. This result was confirmed by real-time PCR and high-resolution melt analysis. Besides improvements in the quality of extracted DNA, use of mineral oil for deparaffinization has the added benefit of decreased time (20 vs. 75 min) and a significant reduction of hands-on labor (1 step vs. multiple hands-on centrifugation and decanting steps).

Mechanistic insights into activation and SOCS3-mediated inhibition of myeloproliferative neoplasm-associated JAK2 mutants from biochemical and structural analyses

JAK2 (Janus kinase 2) initiates the intracellular signalling cascade downstream of cell surface receptor activation by cognate haemopoietic cytokines, including erythropoietin and thrombopoietin. The pseudokinase domain (JH2) of JAK2 negatively regulates the catalytic activity of the adjacent tyrosine kinase domain (JH1) and mutations within the pseudokinase domain underlie human myeloproliferative neoplasms, including polycythaemia vera and essential thrombocytosis. To date, the mechanism of JH2-mediated inhibition of JH1 kinase activation as well as the susceptibility of pathological mutant JAK2 to inhibition by the physiological negative regulator SOCS3 (suppressor of cytokine signalling 3) have remained unclear. In the present study, using recombinant purified JAK2JH1-JH2 proteins, we demonstrate that, when activated, wild-type and myeloproliferative neoplasm-associated mutants of JAK2 exhibit comparable enzymatic activity and inhibition by SOCS3 in in vitro kinase assays. SAXS (small-angle X-ray scattering) showed that JAK2JH1-JH2 exists in an elongated configuration in solution with no evidence for interaction between JH1 and JH2 domains in cis. Collectively, these data are consistent with a model in which JAK2's pseudokinase domain does not influence the activity of JAK2 once it has been activated. Our data indicate that, in the absence of the N-terminal FERM domain and thus cytokine receptor association, the wild-type and pathological mutants of JAK2 are enzymatically equivalent and equally susceptible to inhibition by SOCS3.

Investigation of genetic disturbances in oxygen sensing and erythropoietin signaling pathways in cases of idiopathic erythrocytosis

Background. Idiopathic erythrocytosis is the term reserved for cases with unexplained origins of abnormally increased hemoglobin after initial investigation. Extensive molecular investigation of genes associated with oxygen sensing and erythropoietin signaling pathways, in those cases, usually involves sequencing all of their exons and it may be time consuming. Aim. To perform a strategy for molecular investigation of patients with idiopathic erythrocytosis regarding oxygen sensing and erythropoietin signaling pathways. Methods. Samples of patients with idiopathic erythrocytosis were evaluated for the EPOR, VHL, PHD2, and HIF-2α genes using bidirectional sequencing of their hotspots. Results. One case was associated with HIF-2α mutation. Sequencing did not identify any pathogenic mutation in 4 of 5 cases studied in any of the studied genes. Three known nonpathogenic polymorphisms were found (VHL p.P25L, rs35460768; HIF-2α p.N636N, rs35606117; HIF-2α p.P579P, rs184760160). Conclusion. Extensive molecular investigation of cases considered as idiopathic erythrocytosis does not frequently change the treatment of the patient. However, we propose a complementary molecular investigation of those cases comprising genes associated with erythrocytosis phenotype to meet both academic and genetic counseling purposes.

The landscape of somatic mutations in Down syndrome-related myeloid disorders

Transient abnormal myelopoiesis (TAM) is a myeloid proliferation resembling acute megakaryoblastic leukemia (AMKL), mostly affecting perinatal infants with Down syndrome. Although self-limiting in a majority of cases, TAM may evolve as non-self-limiting AMKL after spontaneous remission (DS-AMKL). Pathogenesis of these Down syndrome-related myeloid disorders is poorly understood, except for GATA1 mutations found in most cases. Here we report genomic profiling of 41 TAM, 49 DS-AMKL and 19 non-DS-AMKL samples, including whole-genome and/or whole-exome sequencing of 15 TAM and 14 DS-AMKL samples. TAM appears to be caused by a single GATA1 mutation and constitutive trisomy 21. Subsequent AMKL evolves from a pre-existing TAM clone through the acquisition of additional mutations, with major mutational targets including multiple cohesin components (53%), CTCF (20%), and EZH2, KANSL1 and other epigenetic regulators (45%), as well as common signaling pathways, such as the JAK family kinases, MPL, SH2B3 (LNK) and multiple RAS pathway genes (47%).