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Physiological Srsf2 P95H expression causes impaired hematopoietic stem cell functions and aberrant RNA splicing in mice

Ayana Kon, Satoshi Yamazaki, Yasuhito Nannya, Keisuke Kataoka, Yasunori Ota, Masahiro Marshall Nakagawa, Kenichi Yoshida, Yusuke Shiozawa, Maiko Morita, Tetsuichi Yoshizato, Masashi Sanada, Manabu Nakayama, Haruhiko Koseki, Hiromitsu Nakauchi and Seishi Ogawa

Key points

  • Blood-specific expression of the Srsf2 P95H mutant results in decreased stem/progenitor cell numbers and a reduced repopulation capacity.

  • Srsf2 P95H mutation by itself is not sufficient to develop MDS, but contributes to the MDS phenotype in transplantation settings.

Abstract

Splicing factor (SF) mutations are characteristic of myelodysplastic syndromes (MDS) and related myeloid neoplasms and implicated in their pathogenesis, but their roles in the development of MDS have not fully been elucidated. Here, we investigated the consequence of mutant Srsf2 expression using newly generated Vav1-Cre-mediated conditional knock-in mice. Mice carrying a heterozygous Srsf2 P95H mutation showed significantly reduced numbers of hematopoietic stem and progenitor cells (HSPCs) and differentiation defects both in the steady-state condition and transplant settings. Srsf2-mutated hematopoietic stem cells (HSCs) showed impaired long-term reconstitution compared to controls in competitive repopulation assays. Although the Srsf2 mutant mice did not develop MDS under the steady-state condition, when their stem cells were transplanted into lethally irradiated mice, the recipients developed anemia, leukopenia and erythroid dysplasia, suggesting the role of replicative stress in the development of an MDS-like phenotype in Srsf2-mutated mice. RNA sequencing of the Srsf2-mutated HSPCs revealed a number of abnormal splicing events and differentially expressed genes, including several potential targets implicated in the pathogenesis of hematopoietic malignancies, such as Csf3r, Fyn, Gnas, Nsd1, Hnrnpa2b1 and Trp53bp1. Among the mutant Srsf2-associated splicing events, most commonly observed were the enhanced inclusion and/or exclusion of cassette exons, which were caused by the altered consensus motifs for the recognition of exonic splicing enhancers. Our findings suggest that the mutant Srsf2 leads to a compromised HSC function by causing abnormal RNA splicing and expression, contributing to the deregulated hematopoiesis that recapitulates the MDS phenotypes, possibly as a result of additional genetic and/or environmental insults.

  • Submitted January 17, 2017.
  • Accepted November 9, 2017.