Murine models with conditional heterozygous expression of splicing factor (SF) mutations (SF3B1, U2AF1, SRSF2, ZRSR2) have confirmed the causative effects of RNA splicing dysregulation in the pathogenesis of myeloid malignancies and CLL (5, 30, 42–45). This evidence concerns the gene SLU7 and B-cell chronic lymphocytic leukemia.