Stem cell differentiation and lineage specification depend on coordinated programs of gene expression, but our knowledge of the chromatin modifying factors regulating these events remains incomplete. Ubiquitination of histone H2A (H2A-K119u) is a common chromatin modification associated with gene silencing, and controlled by the ubiquitin-ligase polycomb repressor complex 1 (PRC1) and H2A-deubiquitinating enzymes (H2A-DUBs). The roles of H2A-DUBs in mammalian development, stem cells, and haematopoiesis have not been addressed. Here we characterized an H2A-DUB targeted mouse line Mysm1-tm1a/tm1a and demonstrated defects in bone marrow haematopoiesis, resulting in lymphopenia, anemia, and thrombocytosis. Development of lymphocytes was impaired from the earliest stages of their differentiation; and there was also a depletion of erythroid cells and a defect in erythroid progenitor function. These phenotypes were due to a cell-intrinsic requirement for Mysm1 in the bone marrow. Importantly, Mysm1-tm1a/tm1a haematopoietic stem cells were functionally impaired, and this was associated with elevated levels of reactive oxygen species, γH2AX DNA damage marker, and p53 protein in the haematopoietic progenitors. Overall these data establish a role for Mysm1 in the maintenance of bone marrow stem cell function, in the control of oxidative stress and genetic stability in haematopoietic progenitors, and in the development of lymphoid and erythroid lineages.
Overall design: Total RNA from different mouse tissues (liver, bone marrow, brain) and cell types (embryonic fibroblasts - MEFs, and embryonic stem cells - ESCs) from wild type, Mysm1+/tm1a (heterozygous), and Mysm1tma1/tm1a (homozygous) mice was analyzed. Tissue and MEFs comparisons are between 3-4 animals per group; ESC comparisons are between three independently passaged samples of wild type, Mysm1+/tm1a, and Mysm1tma1/tm1aES-cells, all on C57BL/6 background. Full allele name: Mysm1tm1a(KOMP)WTSI . This Series includes the data from the cells.
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