Project description:Mammalian aging is associated with multiple defects of hematopoiesis, most prominently with the impaired development of T and B lymphocytes. This defect is thought to originate in hematopoietic stem cells (HSCs) of the bone marrow, specifically due to the age-dependent accumulation of HSCs with preferential megakaryocytic and/or myeloid potential (“myeloid bias”). Here, we tested this notion using inducible genetic labeling and tracing of HSCs in unmanipulated animals. We found that the endogenous HSC population in old mice shows reduced differentiation into all lineages including lymphoid, myeloid, and megakaryocytic. Single-cell RNA sequencing and immunophenotyping (CITE-Seq) showed that HSC progeny in old animals comprised balanced lineage spectrum including lymphoid progenitors. Lineage tracing using the aging-induced HSC marker Aldh1a1 confirmed the low contribution of old HSCs across all lineages. Competitive transplantations of total bone marrow cells with genetically marked HSCs revealed that the contribution of old HSCs was reduced, but compensated by other donor cells in myeloid cells but not in lymphocytes. Thus, the HSC population in old animals becomes globally decoupled from hematopoiesis, which cannot be compensated in lymphoid lineages. We propose that this partially compensated decoupling, rather than myeloid bias, is the primary cause of the selective impairment of lymphopoiesis in older mice.
Project description:Mammalian aging is associated with multiple defects of hematopoiesis, most prominently with the impaired development of T and B lymphocytes. This defect is thought to originate in hematopoietic stem cells (HSCs) of the bone marrow, specifically due to the age-dependent accumulation of HSCs with preferential megakaryocytic and/or myeloid potential ("myeloid bias"). Here we tested this notion used inducible genetic labeling and tracing of HSCs in unmanipulated animals. We found that the endogenous HSC population in old mice shows reduced differentiation into all lineages including lymphoid, myeloid and megakaryocytic. Single-cell RNA sequencing and immunophenotyping (CITE-Seq) showed that HSC progeny in old animals comprised balanced lineage spectrum including lymphoid progenitors. Lineage tracing using the aging-induced HSC marker Aldh1a1 confirmed the low contribution of old HSCs across all lineages. Competitive transplantations of total bone marrow cells with genetically marked HSCs revealed that the contribution of old HSCs was reduced, but compensated by other donor cells in myeloid cells but not in lymphocytes. Thus, the HSC population in old animals becomes globally decoupled from hematopoiesis, which cannot be compensated in lymphoid lineages. We propose that this partially compensated decoupling, rather than myeloid bias, is the primary cause of the selective impairment of lymphopoiesis in the old age.
Project description:Mammalian aging is associated with multiple defects of hematopoiesis, most prominently with the impaired development of T and B lymphocytes. This defect is thought to originate in hematopoietic stem cells (HSCs) of the bone marrow, specifically due to the age-dependent accumulation of HSCs with preferential megakaryocytic and/or myeloid potential ("myeloid bias"). Here we tested this notion used inducible genetic labeling and tracing of HSCs in unmanipulated animals. We found that the endogenous HSC population in old mice shows reduced differentiation into all lineages including lymphoid, myeloid and megakaryocytic. Single-cell RNA sequencing and immunophenotyping (CITE-Seq) showed that HSC progeny in old animals comprised balanced lineage spectrum including lymphoid progenitors. Lineage tracing using the aging-induced HSC marker Aldh1a1 confirmed the low contribution of old HSCs across all lineages. Competitive transplantations of total bone marrow cells with genetically marked HSCs revealed that the contribution of old HSCs was reduced, but compensated by other donor cells in myeloid cells but not in lymphocytes. Thus, the HSC population in old animals becomes globally decoupled from hematopoiesis, which cannot be compensated in lymphoid lineages. We propose that this partially compensated decoupling, rather than myeloid bias, is the primary cause of the selective impairment of lymphopoiesis in the old age.
Project description:During aging, changes in gene expression are associated with decline in physical and cognitive abilities. Here, we investigated the connection between changes of mRNA and protein expression in the brain by comparing the transcriptome and proteome of the mouse cortex during aging. Our transcriptomic analysis revealed that aging mainly triggers gene activation in the cortex. We showed that increase of mRNA expression correlates with protein expression, specifically in the anterior cingulate cortex where we also observed an increase of cortical thickness during aging. Genes exhibiting an aging-dependent increase of mRNA and protein levels are involved in sensory perception and immune functions. Our proteomic analysis also identified changes in protein abundance in the aging cortex and highlighted a subset of proteins that were differentially enriched but exhibited stable mRNA levels during aging, implying the contribution of aging-related post transcriptional and post-translational mechanisms. These specific genes were associated with general biological processes such as translation, ribosome assembly and protein degradation, but also important brain functions related to neuroplasticity. By decoupling mRNA and protein expression, we have thus characterized distinct subsets of genes that differentially adjust to cellular aging in the cerebral cortex.
Project description:Declining immune function with age is associated with reduced lymphoid output of hematopoietic stem cells (HSCs). Currently, there is poor understanding of the dynamic changes with age in the heterogeneous multipotent hematopoietic progenitor cell compartment, which regulates output of differentiated lymphoid cells. In this study, we observed progressive and specific loss of lymphoid-primed multipotent progenitor cells (LMPP/MPP4) as young animals began to age. Single cell RNA-seq revealed a concomitant increase in cycling of these progenitors with loss of a lymphoid priming signature. To interrogate functional multipotency of single cells, we developed a novel, feeder-free in vitro assay to concurrently assess lymphoid and myeloid potential. This assay revealed altered clonal composition of the LMPP/MPP4 compartment with aging, where progenitors with B cell and macrophage-restricted potential are lost while functionally multipotent progenitors are preserved. These results pinpoint an age and cellular compartment to focus further interrogation of the drivers of lymphoid cell loss with aging.