The coexistence of the SRSF2 P95H mutation and RUNX1 deficiency recapitulates multilineage hematopoietic defects and contributes to aberrant DNA damage repair and cell cycle dysregulation in myelodysplastic syndrome (MDS), according to research published in Blood Advances.
“RUNX1 is a master regulator of hematopoiesis, and one of the most frequently mutated transcription factors in MDS, accounting for 10-15% of cases,” the researchers wrote in their report. “Relative to RUNX1, mutations in the splicing factors SRSF2 (aka SC35), SF3B1, U2AF1, and ZRSR2 are exceedingly common in MDS patients, accounting for up to 60% in certain cohorts.”
According to the researchers, mutations in RUNX1 and SRSF2 frequently occur together. Thus, they aimed to understand how double mutation of these functionally divergent genes jointly promote MDS. The team used a murine model with a RUNX1 knockout combined with the SRSF2 P95H mutation to evaluate multilineage hematopoietic defects.
They transplanted mouse bone marrow mononuclear cells collected from control, RUNX1 , SRSF2 P95H, and SRSF2 P95H- RUNX1 double-mutant mice into lethally irradiated wildtype recipients and measured relevant cell counts every 4 weeks, characterized hematopoietic stem and progenitor cells, and quantified gene expression and RNA splicing changes (in both murine and human-derived cells).
The team found that double-mutant mice exhibited anemia as indicated by reduced hemoglobin and red blood cells accompanied with increased mean corpuscular volume, as well as thrombocytopenia. They also demonstrated that double-mutant mice exhibited more pervasive peripheral blood cytopenia than single-mutant mice.
They also observed antagonizing activity of single mutations in specific hematopoietic progenitors. RUNX1 deficiency led to selective expansion of long-term hematopoietic stem cells and various populations of multipotent progenitors (MPPs; CD150–CD48+ MPP2 and CD150+CD48+ MPP3/4 cell populations), while the SRSF2 P95H mutation led to modestly expanded MPP2 and MPP3/4 cells. In the double-mutant mice, expansion of the MPP2 and MPP3/4 cells in the bone marrow was suppressed.
The researchers developed a cellular model based on parallel gene expression and splicing analyses of both human lymphoblast cells (K562) and murine-derived cells. They found that the RUNX1 deficiency was responsible for altered transcription in both single and double-mutants as well as dramatic changes in global splicing. They then showed that only the double mutation induced missplicing of genes selectively enriched in the DNA damage response and cell cycle checkpoint pathways.
“These results illustrate how mutations in a transcription factor and splicing factor can cooperatively promote pathogenesis and support further studies to explore the therapeutic potential of targeting the DNA damage response or aberrant splicing in MDS patients,” the researchers concluded.
Huang YJ, Chen JY, Yan M, et al. RUNX1 deficiency cooperates with SRSF2 mutation to induce multilineage hematopoietic defects characteristic of MDS. Blood Adv. Published online October 7, 2022. doi:10.1182/bloodadvances.2022007804