Mutant U2AF1-induced alternative splicing of H2afy (macroH2A1) regulates B-lymphopoiesis in mice

• Published in: Cell reports (Cambridge) 2021-08, Vol.36 (9), p.109626-109626, Article 109626
• Main Authors: Kim, Sanghyun P., Srivatsan, Sridhar N., Chavez, Monique, Shirai, Cara L., White, Brian S., Ahmed, Tanzir, Alberti, Michael O., Shao, Jin, Nunley, Ryan, White, Lynn S., Bednarski, Jeff, Pehrson, John R., Walter, Matthew J.
• Format: Article
• Language: English
• Subjects: Alternative Splicing; Animals; B-Lymphocytes - immunology; B-Lymphocytes - metabolism; B-lymphopoiesis; Binding Sites; Case-Control Studies; EBF1; H2AFY; HEK293 Cells; hematopoiesis; Histones - genetics; Histones - metabolism; Humans; K562 Cells; Lymphopoiesis; macroH2A1; Mice; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Knockout; Mutation; myelodysplastic syndromes; Myelodysplastic Syndromes - genetics; Myelodysplastic Syndromes - immunology; Myelodysplastic Syndromes - metabolism; Promoter Regions, Genetic; Signal Transduction; spliceosome gene mutations; Splicing Factor U2AF - genetics; Splicing Factor U2AF - metabolism; Trans-Activators - genetics; Trans-Activators - metabolism; U2AF1; U2AF1(S34F)
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2021.109626

Somatic mutations in spliceosome genes are found in ∼50% of patients with myelodysplastic syndromes (MDS), a myeloid malignancy associated with low blood counts. Expression of the mutant splicing factor U2AF1(S34F) alters hematopoiesis and mRNA splicing in mice. Our understanding of the functionally relevant alternatively spliced target genes that cause hematopoietic phenotypes in vivo remains incomplete. Here, we demonstrate that reduced expression of H2afy1.1, an alternatively spliced isoform of the histone H2A variant gene H2afy, is responsible for reduced B cells in U2AF1(S34F) mice. Deletion of H2afy or expression of U2AF1(S34F) reduces expression of Ebf1 (early B cell factor 1), a key transcription factor for B cell development, and mechanistically, H2AFY is enriched at the EBF1 promoter. Induced expression of H2AFY1.1 in U2AF1(S34F) cells rescues reduced EBF1 expression and B cells numbers in vivo. Collectively, our data implicate alternative splicing of H2AFY as a contributor to lymphopenia induced by U2AF1(S34F) in mice and MDS. [Display omitted] •Mutant U2AF1(S34F) induces alternative splicing of H2AFY•H2afy−/− mice have defective B cell development similar to U2AF1(S34F) mice•The H2afy1.1 splice isoform, reduced by U2AF1(S34F), regulates B cell development•H2AFY occupies the Ebf1 promoter, a master regulator of B cell development Kim et al. demonstrate that H2AFY is a functional target of U2AF1(S34F)-induced alternative splicing, a common spliceosome gene mutation in myelodysplastic syndromes. H2afy−/− and U2AF1(S34F) mice have similar defective B cell development. H2AFY occupies the Ebf1 promoter, a key B cell differentiation transcription factor, providing a potential mechanism to regulate its expression.