JAK2 (V617F) as an acquired somatic mutation and a secondary genetic event associated with disease progression in familial myeloproliferative disorders.
BACKGROUND
A somatic gain-of-function mutation of the Janus kinase 2 (JAK2) gene has been identified in chronic myeloproliferative disorders, which appear to have a sporadic occurrence in most individuals. The authors studied the biologic significance of the JAK2 (V617F) mutation in familial myeloproliferative disorders.


METHODS
Twenty pedigrees with familial chronic myeloproliferative disorders were identified through an investigation of family history in 264 patients with sporadic myeloproliferative disorders. A quantitative real-time polymerase chain reaction (qRT-PCR)-based allelic discrimination assay was employed for the detection of the V617F mutation in circulating granulocytes and T lymphocytes. An analysis of X-chromosome inactivation pattern was performed in female patients.


RESULTS
Fourteen families had homogeneous phenotypes, and 6 families had mixed phenotypes. By using a qRT-PCR-based allelic discrimination assay, the JAK2 (V617F) mutation was detected in circulating granulocytes from 20 of 31 patients, but the mutation was not detected in T lymphocytes. Granulocyte mutant alleles ranged from 2.1% to 91.5% and, on average, increased with time. Discordant distribution of the JAK2 (V617F) mutation was observed in siblings with polycythemia vera. The proportion of granulocytes that carried the JAK2 (V617F) mutation was lower than the proportion of clonal granulocytes, as determined in an analysis of X-chromosome inactivation patterns in female patients.


CONCLUSIONS
The current findings indicated that the JAK2 (V617F) mutation represents an acquired somatic mutation in patients with familial chronic myeloproliferative disorders and probably occurs as a secondary genetic event in the background of preexisting clonal hematopoiesis. Thus, a genetic predisposition to acquisition of JAK2 (V617F) is inherited in families with myeloproliferative disorders.
Rumi
Elisa
E
Department of Hematology, Fondazione Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo and University of Pavia School of Medicine, Pavia, Italy.
Passamonti
Francesco
F
Pietra
Daniela
D
Della Porta
Matteo G
MG
Arcaini
Luca
L
Boggi
Sabrina
S
Elena
Chiara
C
Boveri
Emanuela
E
Pascutto
Cristiana
C
Lazzarino
Mario
M
Cazzola
Mario
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D041321:Chromosomes, Human, X / Q000235:genetics*; D018450:Disease Progression; D005260:Female; D005820:Genetic Testing; D006098:Granulocytes / Q000378:metabolism; D006801:Humans; D053614:Janus Kinase 2 / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D009196:Myeloproliferative Disorders / Q000235:genetics*; D010375:Pedigree; D049951:X Chromosome Inactivation / Q000235:genetics
C507924:JAK2 protein, human; D053614:Janus Kinase 2