U2AF1 and acquired polycythemia vera: Indeed, SF3B1 mutations were found in 2.8% and 1.4% (p = 0.011 for ET vs. PV), SRSF2 mutations in 1.5% and 1.8% (p = 0.4 for ET vs. PV), U2AF1 mutations in 1.1% and 0.3% (p = 0.03 for ET vs. PV), ZRSR2 in 0.7% and 1.3% (p = 0.18 for ET vs. PV), of ET and PV respectively.