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RUNX1 Deficiency Cooperates with SRSF2 Mutation to Induce Multi-lineage Hematopoietic Defects Characteristic of Myelodysplastic Syndromes

ABSTRACT: Causal mutations in multiple classes of genes have been identified in MDS patients with some patients harboring more than one mutation. Interestingly, double mutations tend to occur in different classes, rather than the same classes of genes, as exemplified by frequent co-occurring mutations in the transcription factor RUNX1 and the splicing factor SRSF2. Here we report a mouse model in which Runx1 knockout was combined with the Srsf2 P95H mutation to cause multi-lineage hematopoietic defects. Besides their additive and synergistic effects, we also unexpectedly noted a degree of antagonizing activity of single mutations in specific hematopoietic progenitors. To uncover the mechanism, we further developed a cellular model using human K562 cells and performed parallel gene expression and splicing analyses in both human and murine contexts. We performed RNA-seq on sorted Lineage- c-Kit+ (LK) hematopoietic progenitors from bone marrow of mice from WT, runx1 KO , Srsf2 P95H knock in and runx1 Srsf2 P95H double mutants. We also performed RNA-seq on set of isogenic K562 cell lines: wild type (WT), SRSF2 P95H knock-in (SRSF2P95H/+/+), RUNX1 knockdown (RUNX1 KD), and SRSF2 P95H knock-in with RUNX1 knockdown (Double). Strikingly, while RUNX1 deficiency was responsible for altered transcription in both single and double mutants, it also induced dramatic changes in global splicing, as seen with mutant SRSF2, and only their combination induced mis-splicing of genes selectively enriched in the DNA damage response and cell cycle checkpoint pathways. Collectively, these data reveal the convergent impact of a prototypic MDS-associated double mutant on RNA processing and suggest that aberrant DNA damage repair and cell cycle regulation critically contribute to MDS development.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE200446 | GEO | 2022/09/27

REPOSITORIES: GEO

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Project description:Mutations in spliceosomal genes are commonly found in patients with myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). These mutations occur at highly restricted amino acid residues and perturb normal splice site and exon recognition. Spliceosomal mutations are always heterozygous and rarely co-occur with one another, suggesting that cells may only tolerate a partial deviation from normal splicing activity. To test this hypothesis, we generated mice with inducible hemizygous expression of the commonly occurring SRSF2P95H mutation in the hematopoietic system. These mice rapidly developed lethal bone marrow failure upon activation of the Srsf2P95H mutation with concomitant deletion of the wildtype Srsf2 allele, demonstrating that Srsf2-mutant cells depend on the wildtype Srsf2 allele for survival. We next tested whether spliceosomal-mutant leukemias display greater sensitivity to pharmacologic splicing inhibition induced by the small molecule E7107. Treatment of isogenic murine leukemias as well as patient-derived xenograft (PDX) AMLs showed significant reductions in leukemic burden specifically in samples carrying spliceosomal mutations. Collectively, these data provide genetic and pharmacologic evidence that leukemias with spliceosomal mutations are preferentially susceptible to additional splicing perturbations in vivo compared with wildtype counterparts. Modulation of spliceosome function may provide a novel therapeutic avenue in genetically defined subsets of MDS/AML patients. We created an isogenic murine leukemia model by retroviral overexpression of the MLL-AF9 fusion oncogene in Vav-Cre Srsf2+/+ or Vav-Cre Srsf2P95H/+ BM cells followed by transplantation into lethally irradiated recipient mice. In order to determine the mechanistic origins of the Srsf2 mutant-selective effects of E7107, we analyzed transcriptional changes after five consecutive days of E7107 or vehicle treatment in vivo. GFP+ Cd11b+ cells were purified from the BM of recipient mice exactly three hours after the last dose of E7107 and were subjected to paired-end 2x50bp RNA-seq. For the knock-in/knock-out experiments, we generated inducible, hemizygous Srsf2P95H mice to study the effects of wildtype Srsf2 deletion with concomitant activation of the Srsf2P95H allele. Mx1-cre Srsf2fl/+ mice were crossed to Srsf2P95H/+ mice to generate Srsf2 wildtype (Mx1-cre Srsf2+/+), Srsf2 heterozygous knockout (Mx1-Cre Srsf2+/-), Srsf2 heterozygous P95H mutant (Mx1-Cre Srsf2P95H/+), and Srsf2 hemizygous P95H mutant (Mx1-Cre Srsf2P95H/-) mice, which were subjected to single-end 101bp RNA-seq.

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RUNX1 Deficiency Cooperates with SRSF2 Mutation to Induce Multi-lineage Hematopoietic Defects Characteristic of Myelodysplastic Syndromes

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