A

                              Guide to  

                          the Genetics of

                  Polycythaemia Vera (Rubra)

                                   &

                  Essential Thrombocythaemia

                              'PV & ET'



The JAK2 V617F mutation

In 2005 several research groups announced that a genetic mutation had been found to be present in nearly all people wtih PV, and about half of the people with ET. This mutation JAK2 V617F is not present in the normal cells of the body, but only in the 'clone' of cells that is found in PV, ET and some other conditions. The mutation itself is a change of a 'G' (for guanine) to 'T' (for thiamine) in the 617 th. amino acid in the JAK2 gene on chromosome 9. This mutation can also be described using the SNP ID rs77375493. Present blood test can detect cells with the JAK2 V617F mutation when the proportion of clonal cels is perhaps at a 0.1% level (put simply when 1 in 1,000 bone marrow cells belong to the clone); but it would appear very likely that many people would be found to be JAK2 V617F positive if the test were much more sensitive. Just being positive for the JAK2 V617F mutation, but without symptoms, may predispose the person to an increased risk of venous or arterial thrombosis; and prophylaxis with daily aspirin may be appropriate. The amino acid sequence for this mutation can be illustrated as 'YGVCVCGDE' changing to 'YGVCFCGDE' (AA 613-621). or as the bases: 'TAT GGA GTA TGT GTC TGT GGA GAC GAG' changing to 'TAT GGA GTA TGT TTC TGT GGA GAC GAG'