Genotoxic aldehyde stress prematurely ages hematopoietic stem cells in a p53-driven manner
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ABSTRACT: Aged hematopoietic stem cells (HSC) display diminished self-renewal and a myeloid differentiation bias. However, the physiological drivers and molecular processes that underpin this fundamental switch are not understood. HSCs produce formaldehyde and are protected from this metabolite by two tiers of protection: the detoxification enzymes ALDH2 and ADH5 and the Fanconi anemia (FA) DNA repair pathway. Using single cell RNA sequencing, we find that the HSC and progenitor cells in young Aldh2-/- Fancd2-/- mice harbor a transcriptomic signature equivalent to aged wild-type HSCs, along with increased epigenetic age, telomere attrition and myeloid-biased progenitors. In addition, the p53 response is vigorously activated in Aldh2-/- Fancd2-/- HSCs, whilst p53 deletion rescued this aged transcriptomic signature and telomere attrition. Transplantation of single Aldh2-/- Fancd2-/- HSCs also reveals a predominantly myeloid output, which is reversed upon p53 deletion. To further define the origins of the myeloid differentiation bias, a GFP genetic reporter which detects Vwf+ myeloid primed HSCs was crossed into Aldh2-/- Fancd2-/- mice, revealing a striking enrichment of these lineage-biased Vwf+ HSCs. These results indicate that metabolism derived formaldehyde causes endogenous DNA damage which stimulates the p53 response in HSCs, which then accelerates their aging, resulting in a myeloid lineage biased output.
Project description:MTD project_description Inflammation and decreased stem cell function characterize organism aging, yet the relationship between these factors remains incompletely understood. This study shows that aged hematopoietic stem and progenitor cells exhibit increased ground-stage NF-κB activity, which enhances their responsiveness to undergo differentiation and loss of self-renewal in response to inflammation. The study identifies Rad21/cohesin as a critical mediator of NF-κB signals, by increasing chromatin accessibility of inter-/intra-genic and enhancer regions. Rad21/NF-κB are required for normal differentiation, but limit self-renewal of hematopoietic stem cells (HSCs) during aging and inflammation in an NF-κB dependent manner. HSCs from aged mice fail to downregulate Rad21/cohesin and inflammation/differentiation inducing signals in the resolution phase after acute inflammation. and The inhibition of cohesin/NF-κB is sufficient to revert the hypersensitivity of aged HSPCs to inflammation-induced differentiation. During aging, myeloid-biased HSCs with disrupted and naturally occurring reduced expression of Rad21/cohesin are increasingly selected over lymphoid-biased HSCs. Together, Rad21/cohesin mediated NF-κB signaling limits HSPC function during aging and selects for cohesin deficient HSCs with myeloid skewed differentiation.
Project description:Aged hematopoietic stem cells (HSCs) display myeloid-biased differentiation and reduced regenerative potential. In this study, we uncover that P-selectin (Selp) marks a subset of aged HSCs with reduced repopulation capacity. This population of HSCs expresses a prominent aging transcriptome. Overexpression of Selp in young HSCs impaired long-term reconstitution potential and repressed erythropoiesis. We show that IL-1β is elevated in aged bone marrow and administration of IL-1β induces expression of Selp and other aging-associated genes in HSCs. Finally, we demonstrate that transplantation of aged HSCs into young recipients restores a young-like transcriptome, specifically by repressing pro-inflammatory pathways, highlighting the important role of the bone marrow microenvironment in HSC aging.
Project description:The traditional view of hematopoiesis has been that all the cells of the peripheral blood are the progeny of a unitary homogeneous pool of hematopoietic stem cells (HSCs). Recent evidence suggests that the hematopoietic system is actually maintained by a consortium of HSC subtypes with distinct functional characteristics. We show here that myeloid-biased HSCs (My-HSCs) and lymphoid-biased (Ly-HSCs) can be purified according to their capacity for Hoechst dye efflux in combination with canonical HSC markers. We used microarray expression profiling to determine the transcriptional profiles of myeloid-biased lower-SP HSCs and lymphoid-biased upper-SP HSCs Three biological replicates were analyzed for each HSC subpopulation. Lower-SP and upper-SP HSCs were purified from three pools of mice on separate days. HSCs were further purified with the addition of canonical HSC makers; Sca-1+ c-Kit+ Lineage-
Project description:The traditional view of hematopoiesis has been that all the cells of the peripheral blood are the progeny of a unitary homogeneous pool of hematopoietic stem cells (HSCs). Recent evidence suggests that the hematopoietic system is actually maintained by a consortium of HSC subtypes with distinct functional characteristics. We show here that myeloid-biased HSCs (My-HSCs) and lymphoid-biased (Ly-HSCs) can be purified according to their capacity for Hoechst dye efflux in combination with canonical HSC markers. We used microarray expression profiling to determine the transcriptional profiles of myeloid-biased lower-SP HSCs and lymphoid-biased upper-SP HSCs
Project description:Asrij deletion in mice causes loss of HSC quiescence, myeloid skewing, reduced p53 and increased DNA damage, features attributed to aged hematopoietic stem cells (HSCs). To identify the pathways and processes driving the observed HSC aging-like phenotypes upon asrij depletion and to compare the asrij KO transcriptome with aged wild type HSCs, we performed RNA-seq gene expression profiling of Lin- Sca-1+ c-Kit+ CD150+ CD48- stem cells isolated from asrij KO or asrij floxed (control) mouse bone marrow. Our results identify Asrij as a potential driver of aging-like alterations in HSCs and the RNA-seq based transcriptome could help identify additional aging biomarkers and develop strategies to rejuvenate aged HSCs or prevent premature HSC aging.
Project description:Hematopoietic stem cells (HSCs) represent a rare population of cells residing in the Bone Marrow (BM) at the top of hematopoietic hierarchy. A critical balance is maintained between self-renewal and lineage differentiation of HSCs to maintain hematopoietic homeostasis. With aging, this balance is altered with an increase of self-renewal long term HSCs and a myeloid biased differentiation, which favors the appearance of myeloid leukemias and anemias. This experiment aims to understand molecular mechanisms that cause this aged-related disequilibrium in the mouse. To this end, we generated single cell RNA-seq data from pools of young and old hematopoietic stem and progenitor cells (HSPCs), isolated from mouse BMs.
Project description:The tumor suppressor p53 is critical for tumor suppression and other biological events. Yet, the regulatory role of p53 in alcohol-induced fatty liver remains unclear. Here, we show a role for p53 in regulating the ethanol metabolism via acetaldehyde dehydrogenase 2 (ALDH2), a key enzyme responsible for oxidization of alcohol. Through repressing ethanol oxidization, p53 suppresses intracellular levels of acetyl-CoA and histone acetylation, leading to the inhibition of the stearoyl-CoA desaturase-1 (SCD1) gene expression. Mechanistically, p53 directly binds to ALDH2 and prevents the formation of its active tetramer, and indirectly limits the production of pyruvate that promotes the activity of ALDH2. Notably, p53 deficient mice exhibit increased lipid accumulation, which can be reversed by ALDH2 depletion. Moreover, hepatic specific knockdown of SCD1 diminishes ethanol-induced fatty liver caused by p53 loss. By contrast, overexpression of SCD1 in liver promotes ethanol-induced fatty liver development in wildtype mice, while has mild effect on p53-/- or ALDH2-/- mice. Overall, our findings reveal a previously unrecognized function of p53 in alcohol-induced fatty liver, and uncover pyruvate as a natural regulator of ALDH2.
Project description:In the McSC lineage in zebrafish, Aldh2 activity is an important source of formate through its metabolism of its substrate formaldehyde. This formate is required as input into the folate cycle, in particular de novo purine biosynthesis. This scRNA-seq experiment was conducted to investigate the global effects of Aldh2 inhibition on the transcriptomes of isolated McSCs.
Project description:Reactive aldehydes arise as by-products of metabolism, and are normally cleared by multiple families of enzymes. We find that mice lacking two aldehyde detoxifying enzymes, mitochondrial ALDH2 and cytoplasmic ADH5, have greatly shortened lifespans and develop leukemia. Hematopoiesis is profoundly disrupted, with a reduction of hematopoietic stem cells and also common lymphoid progenitors causing a severely depleted acquired immune system. We show that formaldehyde is the common substrate of ALDH2 and ADH5, and establish methods to quantify elevated blood formaldehyde and formaldehyde-DNA adducts in tissues. Bone marrow derived progenitors actively engage DNA repair but also imprint a formaldehyde-driven mutation signature similar to ageing-associated human cancer mutation signatures. Furthermore, we identify analogous genetic defects in children causing a new inherited bone marrow failure and pre-leukemic syndrome. Endogenous formaldehyde clearance alone is therefore critical for hematopoiesis and in limiting mutagenesis in somatic tissues.
Project description:Functional heterogeneity of hematopoietic stem cells (HSCs) heterogeneity has been extensively described in mice, but so far not described in human bone marrow (BM). In particular, HSCs biased towards platelet formation have been identified, and shown to be expanded during ageing and implicated as cells-of-origin for essential thrombocythemia (ET). By combining xenografting of molecularly barcoded adult human BM HSCs and high-throughput single cell RNA sequencing we here identify human BM HSCs that are molecularly and functionally platelet-biased. Furthermore, a quantitative comparison of transcriptomes from young and aged BM HSCs showed that both the proportion of platelet-biased HSCs and their level of molecular platelet priming increases with age.