derivatives suppress TH17 cell differentiation by antagonizing RORgammat activity. Activating mutations in JAK2, a tyrosine kinase that serves as a critical signaling protein for multiple cytokines, are associated with BCR-ABL1–negative myelo-proliferative neoplasms. In this issue of Blood, Zheng and colleagues report that the constitutively activated kinase CK2 binds to JAK2 and is required fo...

The presence of the JAK2 V617F mutation is now part of clinical diagnostic algorithms, and JAK2 status is routinely assessed when BCR/ABL- chronic myeloproliferative neoplasms (MPNs) are suspected. The aim of this study was to evaluate performance of 3 screening and 1 quantitative method for JAK2 V617F detection. For the study, 43 samples (27 bone marrow aspirates and 16 peripheral blood sample...

Activation of Jak tyrosine kinases through hematopoietic cytokine receptors occurs as a consequence of ligand-induced aggregation of receptor-associated Jaks and their subsequent autophosphorylation. Jak kinases consist of a C-terminal tyrosine kinase domain, a pseudokinase domain of unknown function, and Jak homology (JH) domains 3 to 7, implicated in receptor-Jak interaction. We analyzed the ...

BACKGROUND Idiopathic pulmonary fibrosis (IPF) is the most rapidly progressive and fatal fibrotic disorder, with no curative therapies. The signal transducer and activator of transcription 3 (STAT3) protein is activated in lung fibroblasts and alveolar type II cells (ATII), thereby contributing to lung fibrosis in IPF. Although activation of Janus kinase 2 (JAK2) has been implicated in prolifer...

An acquired gain-of-function mutation in the Janus kinase 2 (JAK2-V617F) is frequently found in patients with myeloproliferative disorders (MPDs). To test the hypothesis that JAK2-V617F is the disease-initiating mutation, we examined whether all cells of clonal origin carry the JAK2-V617F mutation. Using allele-specific polymerase chain reaction (PCR) assays for the JAK2 mutation and for the X-...

Essential thrombocythemia (ET) is heterogeneous with respect to natural history, X-chromosome inactivation patterns (XCIPs), and presence of the V617F mutation in Janus kinase 2 (JAK2). We studied 111 patients with ET; 39% were JAK2 mutant positive, and clone size (percentage mutant JAK2) was concordant with XCIP when constitutive T-cell patterns were taken into account. JAK2 mutant clones were...

BACKGROUND Refractory anemia with ringed sideroblasts and marked thrombocytosis (RARS-T) was recently shown to be a JAK2-V617F mutation-related disorder. To determine the frequency and the prognostic significance of this mutation, we retrospectively evaluated 23 patients with platelet counts more than 600 x 10(9)/L, 15% ringed sideroblasts or more, and at least erythroid marrow dysplasia. DES...

Mice lacking a functional Janus kinase 2 (JAK2) allele die embryonically, indicating the mandatory role of JAK2 in basic developmental cellular transcription. Currently, however, the downstream target genes of JAK2 are largely unknown. Here, in vitro conditions were created using a cell line lacking JAK2 expression. Microarray analysis was then used to identify genes that are differentially exp...

To study constitutive Janus kinase signaling, chimeric proteins were generated between the pointed domain of the ets transcription factor TEL and the cytosolic tyrosine kinase Jak2. The effects of these proteins on interleukin-3 (IL-3)– dependent proliferation of the hematopoietic cell line, Ba/F3, were studied. Fusion of TEL to the functional kinase (JH1) domain of Jak2 resulted in conversion ...

Janus kinase 2 (JAK2) is an important mediator of cytokine receptor signaling and plays a key role in the hematopoietic and immune responses. The acquired JAK2 C618R somatic mutation is detected in a subset of myeloproliferative disorders (MPDs) patients and presumed to be a biomarker for MPDs. However, how JAK2 C618R mutation causes MPDs is still unclear. Our results indicate that the amino ac...