{"entity":{"id":"jak2-v617f","kind":"term","name":"JAK2 V617F","aka":[],"tldr":"A single letter change in the JAK2 gene that jams the growth signal for blood cells in the on position. Almost everyone with polycythaemia vera has it, as do about half of those with essential thrombocythaemia or myelofibrosis.","summary":"JAK2 V617F swaps one amino acid (valine for phenylalanine at position 617) in the Janus kinase 2 enzyme, removing its brake so that red cell, platelet and white cell precursors grow without the normal hormone signals. Found in 2005, it is present in about 95 percent of polycythaemia vera and 50 to 60 percent of essential thrombocythaemia and primary myelofibrosis. The share of blood cells carrying it (the allele burden) tracks disease bulk and falls with interferon treatment, which is why it is used as a marker of molecular response.","asOf":"2026-09-16","wikipedia":"https://en.wikipedia.org/wiki/Janus_kinase_2","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Janus_kinase_2"}],"tags":["polycythaemia-vera","mpn"],"related":[],"cancers":["polycythaemia-vera","myeloproliferative-neoplasms"],"sections":[],"technologies":[],"targets":["jak2"],"drugs":["ruxolitinib","ropeginterferon-alfa-2b"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"notes":[],"category":"Clinic basics"},"route":"/terms/jak2-v617f/","neighbours":{"cancer":[{"id":"essential-thrombocythaemia","kind":"cancer","name":"Essential thrombocythaemia (ET)","route":"/cancers/essential-thrombocythaemia/"},{"id":"myeloproliferative-neoplasms","kind":"cancer","name":"Myeloproliferative neoplasms (PV, ET, myelofibrosis)","route":"/cancers/myeloproliferative-neoplasms/"},{"id":"polycythaemia-vera","kind":"cancer","name":"Polycythaemia vera (PV)","route":"/cancers/polycythaemia-vera/"}],"target":[{"id":"jak2","kind":"target","name":"JAK2","route":"/targets/jak2/"}],"drug":[{"id":"ropeginterferon-alfa-2b","kind":"drug","name":"Ropeginterferon alfa-2b","route":"/drugs/ropeginterferon-alfa-2b/"},{"id":"ruxolitinib","kind":"drug","name":"Ruxolitinib","route":"/drugs/ruxolitinib/"}]}}