U2AF1 and myelodysplastic syndrome: Despite being particularly more common in myelodysplastic syndrome (MDS) patients [47], mutations in the splicing factors SF3B1, SRSF2 and U2AF1, between others, represent the second most frequently mutated gene category in MPNs [48], especially in PMF, and have been linked to a higher risk of AML transformation as well as lower overall survival [45].