The Mechanism of Setd2 in Mesenchymal Stromal Cell in MDS-Associated Ineffective Hematopoiety

Myelodysplastic syndrome (MDS) is a heterogeneous, clonal, hematopoietic stem progenitor cell malignant disease. Bone marrow microenvironment participates in the occurrence and development of MDS and plays a key role.

Histone methyltransferase Setd2 is the only enzyme that can catalyze the methylation of mammalian histone H3K36Me3. Previous studies have confirmed that Setd2 is involved in the the transformation of MDS to leukemia, and the expression of S100A9 decreases after Setd2 knockout. This study is based on NHD13 mice with mesenchymal stem cell (MSC) targeted knockout of Setd2. Through experimental methods such as flow cytometry, peripheral blood routine, Wright staining, HE staining, and Gomori staining, it finds that Setd2 targeted knockout mice undergo faster leukemia transformation compared to NHD13 mice; Peripheral blood white blood cells increase, while hemoglobin and platelets decrease; The differentiation of hematopoietic stem progenitor cells in bone marrow is abnormal, with abnormal hematopoiesis and increased blast cells; Spleen fibrosis aggravates and megakaryocyte infiltrates; and Extramedullary hematopoiesis in liver. Through flow cytometry,β- Galactosidase staining and other experimental methods, we finds that compared with NHD13 mice, the MSC morphology of knockout mice is irregular, and the support function for hematopoietic cells is weakened. This study demonstrates that MSC targeted knockout of Setd2 has a promoting effect on the progression of MDS.

We used mass spectrometry to identify proteins that are significantly upregulated in the targeted knockout mouse bone marrow supernatant compared to the NHD13 mouse bone marrow supernatant, and and select the protein Uba5 related to hematopoiesis from them. The expression of Uba5 in the bone marrow supernatant of knockout mice is significantly higher than that in the NHD13 group through WB validation. It is speculated that the hematopoietic changes in Setd2 targeted knockout mice may be related to the downstream target protein Uba5 of Setd2.

This study takes the change of bone marrow microenvironment as an entry point to explore the possible mechanism of MDS ineffective hematopoiesis, hoping to provide microenvironment regulation therapy for some MDS patients with genes that hematopoietic stem cell transplantation that cannot cure(such as TP53, NRAS, KRAS), and provide new ideas for MDS treatment. There are still many limitations in this study, further clinical validation and vivo and vitro rescue experiments on downstream target genes and proteins are still needed in the future.