Alterations in SF3B1 were initially discovered in myelodysplastic syndromes (MDSs) and chronic lymphocytic leukemia (CLL), together with other mutations of splicing factors, such as U2AF1, SRSF2 and ZRSR2 (refs 1, 2, 3). The gene discussed is SF3B1; the disease is B-cell chronic lymphocytic leukemia.