The U2AF1S34F mutation induces lineage-specific splicing alterations in myelodysplastic syndromes

Abstract

Mutations of the splicing factor–encoding gene U2AF1 are frequent in the myelodysplastic syndromes (MDS), a myeloid malignancy, and other cancers. Patients with MDS suffer from peripheral blood cytopenias, including anemia, and an increasing percentage of bone marrow myeloblasts. We studied the impact of the common U2AF1S34F mutation on cellular function and mRNA splicing in the main cell lineages affected in MDS. We demonstrated that U2AF1S34F expression in human hematopoietic progenitors impairs erythroid differentiation and skews granulomonocytic differentiation toward granulocytes. RNA sequencing of erythroid and granulomonocytic colonies revealed that U2AF1S34F induced a higher number of cassette exon splicing events in granulomonocytic cells than in erythroid cells. U2AF1S34F altered mRNA splicing of many transcripts that were expressed in both cell types in a lineage-specific manner. In hematopoietic progenitors, the introduction of isoform changes identified in the U2AF1S34F target genes H2AFY, encoding an H2A histone variant, and STRAP, encoding serine/threonine kinase receptor–associated protein, recapitulated phenotypes associated with U2AF1S34F expression in erythroid and granulomonocytic cells, suggesting a causal link. Furthermore, we showed that isoform modulation of H2AFY and STRAP rescues the erythroid differentiation defect in U2AF1S34F MDS cells, suggesting that splicing modulators could be used therapeutically. These data have critical implications for understanding MDS phenotypic heterogeneity and support the development of therapies targeting splicing abnormalities.

Myeloid Disease Mutations of Splicing Factor SRSF2 Cause G2-M Arrest and Skewed Differentiation of Human Hematopoietic Stem and Progenitor Cells

“…These recipient mice also exhibited increase in bone marrow megakaryocytes. However, the U2AF1 mutations induced defects in the lineage populations are not as impactful and appear to be distinct from those reported in other studies using knock‐in mice and human CD34 + model system . These variations could be caused by the differences in culture conditions including the presence of serum, stroma, and combinations of cytokines.…”

“…These variations could be caused by the differences in culture conditions including the presence of serum, stroma, and combinations of cytokines. The study by Yip et al used separate cultures for granulo‐monocytic and erythroid differentiation . In their study, U2AF1‐S34F was found to skew differentiation toward granulocytes in granulo‐monocytic cultures and cause a block in differentiation in erythroid cultures.…”

“…However, the heterozygous mice themselves exhibited a milder phenotype. Other models using primary human CD34 + HSPCs have also successfully identified increased self‐renewal and abnormal differentiation as cellular phenotypes associated with leukemic chromosomal translocations and somatic mutations . In this study, we examined the impact of myeloid disease mutations in splicing factors SRSF2 and U2AF1 on ex vivo proliferation and myeloid differentiation of primary human CD34 + HSPCs.…”

Knockdown of spliceosome U2AF1 significantly inhibits the development of human erythroid cells

“…U2AF1 ‐ S34F impaired erythroid differentiation and reduced growth of erythroid progenitors in human haematopoietic progenitors. Expression of U2AF1‐S34F in human haematopoietic progenitors leads to the skewing of granulo‐monocytic differentiation towards granulocytes . Different phenotypes were observed in ex vivo cultures of primary human CD34 + cells model, U2AF1 mutations (S34F, Q157R) skew granulo‐monocytic differentiation towards monocytes.…”

“…Reports on analysis of MDS patients have revealed a high incidence of U2AF1‐S34F missense mutation . The study shows that overexpression of this U2AF1‐S34F mutant impairs erythroid differentiation and skews granulomonocytic differentiation towards granulocytes in human haematopoietic progenitors . Depletion of U2AF1 affects the alternative splicing of the Dscam gene transcript in Drosophila .…”