The effect of U2AF1 mutation on erythroid differentiation and sensitivity to demethylation drug treatment

Myelodysplastic syndrome (MDS) is a group of blood disorders characterized by impaired maturation of erythroid cells. Mutations in the U2 small nuclear RNA auxiliary factor 1 (U2AF1) gene, particularly S34 (S34F/Y) and Q157 (Q157P/R), have been identified in 5-10% of MDS patients. By analyzing U2AF1 expression in hematopoietic stem progenitor cells and different blood cells in the GEO database, we have found the expression pattern of U2AF1 showed a significant stage specificity during normal erythropoiesis. To explore the specific impact of U2AF1 alterations on cellular function, we transduced K562 cells with lentivirus carrying four different types of U2AF1 mutants. Our results showed that these mutations significantly inhibited the growth of K562 cells. Mutations at the S34 sites (S34F and S34Y) reduced the mRNA expression levels of erythroid-related transcription factors GATA1, NF-E2, EKLF, and GFI-1B. The proportion of cells with CD71^lowCD235a^hig decreased, as well as the content of hemoglobin in K562 cells. In contrast, mutations at the Q157 site had opposite effects on these expression levels in K562 cells. Furthermore, we classified patients' risk ratings into three categories based on IPSS-R: moderate high-risk MDS, high-risk MDS, and very high-risk MDS. A total of 12 patients were analyzed, including 5 at moderate high-risk and 3 patients carrying mutations. Among 3 high-risk individuals, only one carried a mutation. 4 individuals at very high-risk, with 0 patients carrying the mutation. MDS patients with U2AF1 mutations (S34F, S34Y, Q157P, R156H) had significantly lower white blood cell, hemoglobin, and platelet counts than the MDS patients without these alterations. We hypothesize that treatment with Azacitidine (AZA) may lead to better recovery levels of hemoglobin and platelets for patients with U2AF1 mutations. Meanwhile, we found that U2AF1-mutated MDS patients have better responsiveness to demethylating drugs. We isolated and cultured peripheral blood mononuclear cells (PBMCs) carrying the U2AF1 S34F mutation from a high-risk MDS patient with a 7q chromosome deletion. The demethylating drug AZA could significantly inhibit their proliferation and induce apoptosis in the MDS PBMCs. In summary, our research demonstrated the following: (1) The effect of U2AF1 mutation on erythrocyte differentiation that S34 mutation inhibits the differentiation process, but the Q157 mutation promotes the differentiation process. (2) The level of erythrocyte changes in U2AF1-mutated MDS patients should receive more attention. (3) It also showed that demethylating drugs have promising therapeutic effects in treating MDS patients carrying U2AF1 mutations.