3/28/2023 0 Comments Ev nova x2 mode![]() ![]() ![]() Importantly, the protein levels of many ribosomal proteins were also significantly reduced ( Figure 2E). ![]() Moreover, gene set enrichment analysis (GSEA) reinforced the finding that genes involved in translation initiation and ribosome formation were significantly depleted in MYSM1-edited HSCs ( Figures 2D and S2B Tables S1 and S2). Given that this downregulation appeared to be subtle, we confirmed that the expression of various ribosomal proteins and eukaryotic initiation factor (EIF) encoding mRNAs was significantly reduced in CD34 +CD45RA −CD90 + cells ( Figure S2A). To begin to define how MYSM1 loss can compromise human HSC function, we examined the scRNA-seq data for those cells that had the molecular HSC signature and found that there was a significant downregulation of gene sets and genes implicated in ribosomal biogenesis and translation regulation ( Figures 2A–2C). Reduced protein synthesis rates in HSCs with MYSM1 loss Importantly, this model enabled us to ask critical questions about the molecular basis for HSC loss in this disorder, which remains enigmatic despite a number of phenotypic studies in mouse models. Collectively, this data confirmed that normal MYSM1 expression is essential for human HSC maintenance both in vitro and in vivo, and genome editing of MYSM1 in HSPCs can faithfully recapitulate the bone marrow failure phenotypes observed in patients with biallelic mutations. Analysis of all major lineages confirmed that the repopulation defect broadly impacted all lineages ( Figure 1G). Based upon both the reduced bone marrow engraftment (∼2.5-fold reduction) and depletion of MYSM1-edited alleles (∼3-fold reduction), we estimate an ∼8-fold loss of HSCs. Importantly, the overall editing efficiency of cells was also dramatically reduced compared with CD34 + HSPCs before transplantation ( Figure 1F), suggesting a strong selection against MYSM1 deficient cells. Graphical abstractĬonsistent with the in vitro HSC depletion phenotype, there was significantly lower human CD45 + cell engraftment in the peripheral blood, bone marrow, and spleen at 4 months post-transplantation ( Figures 1E and S1E) when hematopoiesis will predominantly be driven by transplanted HSCs. Increasing protein synthesis rates via MYSM1 overexpression makes HSCs less susceptible to ferroptosis, more broadly illustrating the selective vulnerabilities that arise in somatic stem cell populations as a result of physiologic adaptations. ![]() Importantly, this selective vulnerability to ferroptosis not only underlies HSC loss in MYSM1 deficiency but also characterizes a broader liability of human HSCs. HSC maintenance can be fully rescued by blocking ferroptosis, despite no alteration in protein synthesis rates. Here, inspired by a bone marrow failure disorder due to the loss of the histone deubiquitinase MYSM1, characterized by selectively disadvantaged HSCs, we show how reduced protein synthesis in HSCs results in increased ferroptosis. Yet, the precise vulnerabilities that arise from such adaptations have not been fully characterized. Hematopoietic stem cells (HSCs) have a number of unique physiologic adaptations that enable lifelong maintenance of blood cell production, including a highly regulated rate of protein synthesis. ![]()
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