U2AF1 and myelodysplastic syndrome: Over half of all patients with MDS carry spliceosome gene mutations (6, 7), with splicing factor 3b subunit 1 (SF3B1), serine and arginine–rich splicing factor 2 (SRSF2), U2 small nuclear RNA auxiliary factor 1 (U2AF1), and zinc finger CCCH-type, RNA-binding motif and serine/arginine rich 2 (ZRSR2) being the most frequently mutated splicing factor genes (6).