3194 - SRSF2 P95h Mutation Promotes Myeloid Biased Hematopoiesis and Initiates Myeloproliferative/Myelodysplastic Syndromes From Hematopoietic Stem Cells

Abstract

Myelodysplastic syndromes (MDS) are a collection of heterogeneous clonal stem cell disorders that lead to ineffective hematopoiesis and multi-lineage cytopenia. Treatment options for MDS patients are limited and its pathogenesis remains unelucidated. In recent years, sequencing studies have uncovered recurrent mutations in MDS. Particularly, mutations in the RNA splicing machinery have generated great interest since it is one of the most frequently mutated pathways. Mutations of SRSF2, a spliceosome component, are found in high-risk MDS (12–15%) or chronic myelomonocytic leukaemia (CMML; 40–50%)- an aggressive myeloproliferative neoplasm. Thus, there is a necessity to understand the effect of SRSF2 mutation on hematopoiesis and generate pre-clinical models that faithfully reproduce human MDS. Here, we described the establishment and characterisation of a conditional knock-in Srsf2P95H model that closely resembles human MDS and myeloproliferative neoplasms (MPN). By using Rosa26Cre-mediated activation, we demonstrated that Srsf2P95H mutation led to macrocytic anaemia, myeloid bias at the expense of lymphopoiesis, and morphological dysplasia, characteristics of human MDS. Similar phenotypes were observed in hSclCreER model which activates Srsf2P95H mutation in hematopoietic stem cells. Twenty weeks post activation, hematopoietic stem and progenitor populations (HSPCs, lin-, c-Kit+) were sorted from hSclCreERTg/ + R26eYFP Srsf2P95H/ + and Srsf2 +/+ mice and RNA-sequenced. We found a repression of lymphoid-related genes (Lck, Ly6d, Blk), as well as up-regulation of myeloid-related genes (Hmga2). There was a down-regulation of Bcl211 (Bim), a pro-apoptotic factor, in Srsf2P95H/ + . Gene expression changes were validated on an independent set of HSPCs cells from Rosa26Cre Srsf2 transplant recipients. Pathway analysis confirmed enrichment of myeloid-related pathways and the activation of pathways associated with human MDS in Srsf2P95H samples. Overall, our mice model demonstrated that Srsf2P95H causes myeloid bias at the expense of lymphoid and is sufficient to initiate MDS.