The Effects of Necroptosis in Bone Marrow Inflammation in Mouse Models of Myelodysplastic Syndromes

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Green, Emily
Dugger, Teresa
Hassan, Yuliya
Ramos-Narváez, Michelle
Zinkel, Sandra
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Scholarship Sewanee 2020 , Cancer , Biology , Hematology , Oncology , Myelodysplastic syndromes
Myelodysplastic syndromes (MDS) are a group of conditions that result when blood-forming cells in the bone marrow function abnormally and result in low numbers of one or more types of blood cells. MDS is a form of blood cancer, and in some cases progresses to leukemia. MDS patients have low blood counts despite elevated numbers of cells in bone marrow due to increased necroptotic cell death. Necroptosis contributes to the observed inflammation and may also contribute to bone marrow failure in MDS patients. Activation of the TNF⍺ family surface receptors in certain situations leads to necroptosis driven by Ripk1. Consequently, necroptosis leads to inflammation due to the release of intracellular contents in the extracellular space. Inflammatory cytokines, including TNF⍺, in turn further activate necroptosis. The Asxl1 gene frequently has a mutated early driver mutation of MDS and leukemia and is thought to be involved in the inflammatory cytokine response, however its function is not yet fully known. Knockout mouse models for the Asxl1 gene were used to analyze the production of cytokines. Through immunofluorescence and flow cytometry, we discovered a population of Immature Myeloid cells that exhibit interesting and consistent cytokine production and determined that ASXL1 cells have increased cytokine production in all investigated cytokines, including TNF⍺. To test whether inhibiting necroptosis may improve bone marrow function and inflammation in VavAsxl1 F/F mice, Ripk1 function was genetically inhibited (Vav Asxl1F/F Ripk1). We show that when RIPK1 kinase activity was knocked down, the production of TNF⍺ decreased to near wild type levels, and SRSF2 P95 tissue exhibited increased TNF⍺ production. We will define and investigate the immature myeloid population, using surface markers, to probe their role in inflammation associated with MDS in future experiments. Overall, this study should lead to a greater understanding of necroptosis in bone marrow inflammation that is observed in MDS.