Key Points RUNX1a, but not RUNX1b, is overexpressed in CD34+ cells from patients with myelodysplastic/myeloproliferative neoplasms. SRSF2P95H mutation induces RUNX1a overexpression and a monocytic phenotype in TF-1 cells.

Splicing factor gene mutations are found in 60-70% of patients with myelodysplastic syndromes (MDS).We investigated the effects of splicing factor gene mutations on the diagnosis, patient characteristics, and prognosis of MDS. A total of 106 patients with MDS were included. The percentage of patients with MDS with ring sideroblasts (14.15%) as per the 2017 WHO classification was significantly higher than that of patients with refractory anemia with ring sideroblasts (2.88%) as per the 2008 WHO classification (P = 0.005). Splicing factor mutations were detected in 32 patients (13 SF3B1, 8 U2AF1, and 11 SRSF2), and the mutations were mutually exclusive. Significant differences were observed in the mean corpuscular volume, platelet count, bone marrow myeloid:erythroid ratio, and megakaryocyte count in patients with different mutations. SRSF2 mutations were associated with a high cumulative incidence of red blood cell transfusion dependence, while SF3B1 mutations were associated with a low cumulative incidence of platelet concentrate transfusion dependence. Presence of SF3B1 mutation was a significant univariate predictor of overall survival, but become nonsignificant in the multivariate model. Although many factors also could affect survival, these results suggest that splicing factor mutations contribute to distinct MDS phenotypes, including patient characteristics and clinical courses.