These mutations commonly occur in splicing factor 3b subunit 1 (SF3B1), serine/arginine-rich splicing factor 2 (SRSF2), and U2 small nuclear RNA auxiliary factor 1 (U2AF1), and the genetic data in MDS suggest that these alterations are critical to disease pathogenesis (23). This evidence concerns the gene U2AF1 and myelodysplastic syndrome.