U2AF1 and myeloproliferative disorder: For the whole MPN group, only mutations in five genes correlated significantly with inferior overall survival, ASXL1 (P=0.0005), SRSF2 (P<0.0001), U2AF1 (P<0.0001), CBL (P=0.01) and SF3B1 (P<0.0001) (Figure 3).