Project description:Aging of hematopoietic stem cells (HSCs) leads to several functional changes, including alterations affecting self-renewal and differentiation. While it is well established that many of the age-induced changes are intrinsic to HSCs, less is known about the stability of this state. Here, we entertained the hypothesis that HSC aging is driven by the acquisition of permanent genetic mutations. To examine this issue at a functional level in vivo, we applied induced pluripotent stem (iPS) cell reprogramming of aged hematopoietic progenitors and allowed the resulting aged-derived iPS cells to reform hematopoiesis via blastocyst complementation. Next, we functionally characterized iPS-derived HSCs in primary chimeras and following the transplantation of 're-differentiated' HSCs into new hosts; the gold standard to assess HSC function. Our data demonstrate remarkably similar functional properties of iPS-derived and endogenous blastocyst-derived HSCs, despite the extensive chronological and proliferative age of the former. Our results therefore favor a model in which an underlying, but reversible, epigenetic component is a hallmark of HSC aging rather than being driven by an increased DNA mutation burden. Hematopoietic stem cells (HSC) have been sorted out from young and aged steady-state mice, and from recipients transplanted with young and aged bone marrow. Generated iPS and commercially available ES cells were also sorted and analyzed.
Project description:Epigenetic modifications are thought to be important for gene expression changes during development and aging. However, besides the Sir2 histone deacetylase in somatic tissues and H3K4 trimethylation in germlines, there is scant evidence implicating epigenetic regulations in aging. The insulin/IGF-1 signaling (IIS) pathway is a major lifespan regulatory pathway. Here we show that progressive increases in gene expression and loss of H3K27me3 on IIS components are due, at least in part, to increased activity of the H3K27 demethylase UTX-1 during aging. RNAi of the utx-1 gene extended the mean lifespan of C. elegans by ~30%, dependent on DAF-16 activity and not additive in daf-2 mutants. The loss of utx-1 increased H3K27me3 on the Igf1r/daf-2 gene and decreased IIS activity leading to a more "naive" epigenetic state. Like stem cell reprogramming, our results suggest that reestablishing epigenetic marks lost during aging might help "reset" the developmental age of animal cells. Examination of H3K27me3 in young and old worms without or with Utx-1 RNAi.
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:Aging of hematopoietic stem cells (HSCs) leads to several functional changes, including alterations affecting self-renewal and differentiation. While it is well established that many of the age-induced changes are intrinsic to HSCs, less is known about the stability of this state. Here, we entertained the hypothesis that HSC aging is driven by the acquisition of permanent genetic mutations. To examine this issue at a functional level in vivo, we applied induced pluripotent stem (iPS) cell reprogramming of aged hematopoietic progenitors and allowed the resulting aged-derived iPS cells to reform hematopoiesis via blastocyst complementation. Next, we functionally characterized iPS-derived HSCs in primary chimeras and following the transplantation of 're-differentiated' HSCs into new hosts; the gold standard to assess HSC function. Our data demonstrate remarkably similar functional properties of iPS-derived and endogenous blastocyst-derived HSCs, despite the extensive chronological and proliferative age of the former. Our results therefore favor a model in which an underlying, but reversible, epigenetic component is a hallmark of HSC aging rather than being driven by an increased DNA mutation burden.
Project description:Aging is associated with functional decline of hematopoietic stem cells (HSC) as well as an increased risk of myeloid malignancies. We performed an integrative characterization of epigenomic and transcriptomic changes, including single-cell RNA-seq, during normal human aging. Lineage-CD34+CD38- cells (HSC-enriched, HSCe) undergo age-associated epigenetic reprogramming consisting of redistribution of DNA methylation and reductions in H3K27ac, H3K4me1 and H3K4me3. This reprogramming of aged HSCe globally targets developmental and cancer pathways which are comparably altered in AML of all ages; encompassing loss of 4,656 active enhancers, 3,091 bivalent promoters, and deregulation of several epigenetic modifiers and key hematopoietic transcription factors, such as KLF6, BCL6 and RUNX3. Notably, in vitro downregulation of KLF6 results in impaired differentiation, increased colony forming potential and changes in expression that recapitulate aging and leukemia signatures. Thus, age-associated epigenetic reprogramming may form a predisposing condition for the development of age-related AML.
Project description:Aging is associated with functional decline of hematopoietic stem cells (HSC) as well as an increased risk of myeloid malignancies. We performed an integrative characterization of epigenomic and transcriptomic changes, including single-cell RNA-seq, during normal human aging. Lineage-CD34+CD38- cells (HSC-enriched, HSCe) undergo age-associated epigenetic reprogramming consisting of redistribution of DNA methylation and reductions in H3K27ac, H3K4me1 and H3K4me3. This reprogramming of aged HSCe globally targets developmental and cancer pathways which are comparably altered in AML of all ages; encompassing loss of 4,656 active enhancers, 3,091 bivalent promoters, and deregulation of several epigenetic modifiers and key hematopoietic transcription factors, such as KLF6, BCL6 and RUNX3. Notably, in vitro downregulation of KLF6 results in impaired differentiation, increased colony forming potential and changes in expression that recapitulate aging and leukemia signatures. Thus, age-associated epigenetic reprogramming may form a predisposing condition for the development of age-related AML.
Project description:Aging is associated with functional decline of hematopoietic stem cells (HSC) as well as an increased risk of myeloid malignancies. We performed an integrative characterization of epigenomic and transcriptomic changes, including single-cell RNA-seq, during normal human aging. Lineage-CD34+CD38- cells (HSC-enriched, HSCe) undergo age-associated epigenetic reprogramming consisting of redistribution of DNA methylation and reductions in H3K27ac, H3K4me1 and H3K4me3. This reprogramming of aged HSCe globally targets developmental and cancer pathways which are comparably altered in AML of all ages; encompassing loss of 4,656 active enhancers, 3,091 bivalent promoters, and deregulation of several epigenetic modifiers and key hematopoietic transcription factors, such as KLF6, BCL6 and RUNX3. Notably, in vitro downregulation of KLF6 results in impaired differentiation, increased colony forming potential and changes in expression that recapitulate aging and leukemia signatures. Thus, age-associated epigenetic reprogramming may form a predisposing condition for the development of age-related AML.
Project description:Aging is associated with functional decline of hematopoietic stem cells (HSC) as well as an increased risk of myeloid malignancies. We performed an integrative characterization of epigenomic and transcriptomic changes, including single-cell RNA-seq, during normal human aging. Lineage-CD34+CD38- cells (HSC-enriched, HSCe) undergo age-associated epigenetic reprogramming consisting of redistribution of DNA methylation and reductions in H3K27ac, H3K4me1 and H3K4me3. This reprogramming of aged HSCe globally targets developmental and cancer pathways which are comparably altered in AML of all ages; encompassing loss of 4,656 active enhancers, 3,091 bivalent promoters, and deregulation of several epigenetic modifiers and key hematopoietic transcription factors, such as KLF6, BCL6 and RUNX3. Notably, in vitro downregulation of KLF6 results in impaired differentiation, increased colony forming potential and changes in expression that recapitulate aging and leukemia signatures. Thus, age-associated epigenetic reprogramming may form a predisposing condition for the development of age-related AML.
Project description:Aging is associated with functional decline of hematopoietic stem cells (HSC) as well as an increased risk of myeloid malignancies. We performed an integrative characterization of epigenomic and transcriptomic changes, including single-cell RNA-seq, during normal human aging. Lineage-CD34+CD38- cells (HSC-enriched, HSCe) undergo age-associated epigenetic reprogramming consisting of redistribution of DNA methylation and reductions in H3K27ac, H3K4me1 and H3K4me3. This reprogramming of aged HSCe globally targets developmental and cancer pathways which are comparably altered in AML of all ages; encompassing loss of 4,656 active enhancers, 3,091 bivalent promoters, and deregulation of several epigenetic modifiers and key hematopoietic transcription factors, such as KLF6, BCL6 and RUNX3. Notably, in vitro downregulation of KLF6 results in impaired differentiation, increased colony forming potential and changes in expression that recapitulate aging and leukemia signatures. Thus, age-associated epigenetic reprogramming may form a predisposing condition for the development of age-related AML.