Project description:Proposals for induced glia-to-neuron conversion have raised the potential for generating new neurons to replace those lost due to injury, aging or neurodegenerative diseases. Here, single-cell spatial transcriptomics [Multiplexed Error Robust Fluorescence In Situ Hybridization (MERFISH)] is used to construct a spatial cell atlas of the subventricular and dentate gyrus neurogenic niches of young and aged adult murine brain. RNAs that encode the RNA binding protein Polypyrimidine Tract-Binding Protein (PTBP1) in the aged murine brain are determined to be highest in glia that line previously active neurogenic niches. A glial cell population with ependymal character within an initially quiescent subventricular neurogenic niche in the aged murine brain is identified that upon transient suppression of PTBP1 reenters the cell cycle, replicates DNA, and converts into neurons through a canonical adult neurogenesis pathway. Glia-derived neurons migrate from this niche, with some neurons transiting to the striatum and acquiring a transcriptome characteristic of GABAergic inhibitory neurons. Similar PTBP1 expressing quiescent glia are identified in the corresponding neurogenic niche of aged human brain. Thus, transient reduction of PTBP1 holds potential for inducing the generation of new neurons in quiescent neurogenic niches of the aged nervous system, thereby offering promising therapeutic applications.
Project description:We report that the two adult neurogenic niches of the mammalian brain – the dentate gyrus of the hippocampal formation and the subependymal zone of the lateral ventricles - displayed differential vulnerability to increased FoxG1 dosage: high FoxG1 levels severely compromised survival and glutamatergic dentate granule neuron fate acquisition in the hippocampal neurogenic niche, but left neurogenesis of GABAergic neurons in the subependymal zone / olfactory bulb system unaffected. Comparative transcriptomic analyses revealed a significantly higher expression of the apoptosis-linked nuclear receptor Nr4a1 in FoxG1-overexpressing hippocampal neural precursors. Our results reveal differential vulnerability of neuronal subtypes to increased FoxG1 dosage and suggest that activity of a FoxG1/Nr4a1 axis contributes to such subtype-specific response.
Project description:Neural stem cells (NSCs) generating new neurons are restricted to few niches in the adult mammalian brain, while the remainder rather promotes gliogenesis. Here we take advantage of the spatial separation of an NSC niche (the subependymal zone) and the region to where the newly generated neurons migrate and integrate (the olfactory bulb). Using state-of-the-art mass spectrometry we present a comprehensive proteomic characterization of these niches compared to a region of the normal brain parenchyma (cerebral cortex) that is not contusive to neurogenesis and new neuron integration. We find unique compositions of regulatory ECM components in the neurogenic niche, with quiescent NSCs as a main source of their local ECM, including the multi-functional enzyme transglutaminase 2 that we identify as crucial for neurogenesis. Atomic force microscopy further corroborates indications from the proteome that neurogenic niches are significantly stiffer than the non-neurogenic parenchyma, highlighting the unique properties of these special niches.
Project description:Purpose: Compare the transcriptome of hematopoietic stem cells (HSCs) that were aged in old and young niches Methods: barcoded GFP+ HSCs were FACS-sorted from a) three recipient mice 15 months post transplantation, and b) six serial transplantation recipient mice 5 months after the 8th transplantation, then subjected to processed using the Chromium Single-cell 3′ v2 Library Kit (10× Genomics, Pleasanton, CA) following the manufacturer’s instructions Results: we obtained transcriptomes of about 12k HSCs aged in young niche, and about 10k HSCs aged in old niche, with the average sequencing depth at close to 50k reads per cell Conclusions: we identified striking differences in gene expression profiles 1) between HSCs aged in young niches from mice with early aging and from mice with delayed aging, and 2) between HSCs aged in old niches and young niches when mice exhibited hematopoietic aging phenotype
Project description:Epigenetic alterations are a key hallmark of aging but have not been extensively explored in tissues. Here, using naturally aged murine liver as a model and extending study to other quiescent tissues, we find that aging is driven by temporal chromatin alterations that promote a refractory cellular state and compromise cellular identity. Using an integrated multi-omics approach and the first direct visualization of aged chromatin, we find that old cells show global H3K27me3-driven broad heterochromatinization and transcription suppression. At the local level, site-specific loss of H3K27me3 from promoters of genes encoding developmental transcription factors leads to expression in liver of non-hepatocyte markers. Interestingly, liver regeneration reverses H3K27me3 patterns and rejuvenates multiple molecular and physiological aspects of the aged liver.
Project description:The mechanisms responsible for determining neural stem cell fate are numerous and complex. To begin to identify the specific components involved in these processes, we generated several mouse neural stem cell (NSC) antibodies against cultured mouse embryonic neurospheres. Our immunohistochemical data showed that the NSC-6 antibody recognized NSCs in the developing and postnatal murine brains as well as in human brain organoids. Mass spectrometry revealed the identity of the NSC-6 epitope as brain abundant, membrane-attached signal protein 1 (BASP1), a signaling protein that plays a key role in neurite outgrowth and plasticity. Western blot analysis using the NSC-6 antibody demonstrated multiple BASP1 isoforms with varying degrees of expression and correlating with distinct developmental stages. Herein, we describe the expression of BASP1 in NSCs in the developing and postnatal mammalian brains and human brain organoids, and demonstrate that the NSC-6 antibody may be a useful marker of these cells.
Project description:Hematopoietic stem cells (HSCs) are maintained in the quiescent state for protection from exhaustion by a number of self-renewal divisions. To understand the in vivo kinetics of quiescent HSCs, we analyzed the cell cycle of CD201+150+48-Lin-Kit+Sca-1+ cells after transplantation and during development and aging using fluorescent ubiquitination-based cell cycle indicator (Fucci) mice to distinguish HSCs at the G0, G1, and S/G2/M phases. The quiescent HSC population, representing a functional HSC pool, rapidly expanded by three weeks after transplantation and by three weeks of age in development and gradually accumulated in bone marrow with aging. Single-cell RNA-sequencing with flow cytometric index sorting suggested that high CD201 and Sca-1 expression levels and a low level of mitochondrial activity were associated with quiescent HSCs. A novel set of candidate quiescent genes in HSCs was also provided. This study implied that controlling quiescent HSCs is important for the in vivo expansion and maintenance of functional HSCs.