Project description:A new population of dysfunctional astrocytes in the aging mouse hippocampus called autophagy-dysregulated astrocytes (APDAs) show impaired protein homeostasis and defective regulation of synapse formation and elimination and appear early in a mouse model of Alzheimer’s disease.
Project description:Normal brain aging is marked by a cognitive decline, spurred by changes in cellular metabolism and homeostatic dysregulation, as well as modifications in synapses and neuronal connectivity. Astrocytes are well positioned as an effector of these changes, although how properties of astrocytes change with age remains unclear. Here, we address this question by profiling astrocytic gene expression from multiple brain regions of adult (4 month-old) and aged (2 years-old) mice. We isolated mRNA from transgenic mice where ribosomes within astrocytes were genetically tagged (GFAP-cre x RPL22-HA, astrocyte ribotag). We then used RNA sequencing to identify and quantify the astrocyte-enriched mRNA, analyzing 4 different brain regions: visual cortex, somatomotor cortex, hypothalamus, and cerebellum. Overall, we find that astrocyte expression of inflammatory and immune response factors increase with age, as well as changes in genes associated with metabolism, cholesterol synthesis, and synaptogenesis. Going forward, these data contribute to an understanding of astrocyte diversity and provide insight into the role of astrocytes in normal aging.
Project description:Neuroinflammation is a common feature of neurodegenerative disorders such as Alzheimer's disease (AD). Neuroinflammation is induced by dysregulated glial activation, and astrocytes, the most abundant glial cells, become reactive upon neuroinflammatory cytokines released from microglia, and actively contribute to neuronal loss. Therefore, blocking reactive astrocyte functions is a viable strategy to manage neurodegenerative disorders. However, factors or therapeutics directly regulating astrocyte subtype remain unexplored. Here, we identified transcription factor NF-E2-related factor 2 (Nrf2) as a therapeutic target in neurotoxic reactive astrocytes upon neuroinflammation. We found that the absence of Nrf2 promoted the activation of reactive astrocytes in the brain tissue samples obtained from AD model 5xFAD mice, whereas enhanced Nrf2 expression blocked the induction of reactive astrocyte gene expression by counteracting NF-kB subunit p65 recruitment. Neuroinflammatory astrocytes robustly upregulated genes associated with type I interferon and the antigen-presenting pathway, which were suppressed by Nrf2 pathway activation. Moreover, impaired cognitive behaviors observed in AD mice were rescued upon ALGERNON2 treatment, which potentiated Nrf2 pathway and reduced the induction of neurotoxic reactive astrocytes. Thus, we highlight the potential of astrocyte-targeting therapy by promoting the Nrf2 pathway signaling for neuroinflammation-triggered neurodegeneration.
Project description:Neuroinflammation is a common feature of neurodegenerative disorders such as Alzheimer's disease (AD). Neuroinflammation is induced by dysregulated glial activation, and astrocytes, the most abundant glial cells, become reactive upon neuroinflammatory cytokines released from microglia, and actively contribute to neuronal loss. Therefore, blocking reactive astrocyte functions is a viable strategy to manage neurodegenerative disorders. However, factors or therapeutics directly regulating astrocyte subtype remain unexplored. Here, we identified transcription factor NF-E2-related factor 2 (Nrf2) as a therapeutic target in neurotoxic reactive astrocytes upon neuroinflammation. We found that the absence of Nrf2 promoted the activation of reactive astrocytes in the brain tissue samples obtained from AD model 5xFAD mice, whereas enhanced Nrf2 expression blocked the induction of reactive astrocyte gene expression by counteracting NF-kB subunit p65 recruitment. Neuroinflammatory astrocytes robustly upregulated genes associated with type I interferon and the antigen-presenting pathway, which were suppressed by Nrf2 pathway activation. Moreover, impaired cognitive behaviors observed in AD mice were rescued upon ALGERNON2 treatment, which potentiated Nrf2 pathway and reduced the induction of neurotoxic reactive astrocytes. Thus, we highlight the potential of astrocyte-targeting therapy by promoting the Nrf2 pathway signaling for neuroinflammation-triggered neurodegeneration.
Project description:scRNA-seq of electrophysiologically characterized DRG neurons reveals subtype-specific and maturational differences in gene expression
Project description:Multiple sclerosis (MS) is a debilitating demyelinating disease characterized by remyelination failure attributed to inadequate oligodendrocyte precursor cells (OPCs) differentiation and aberrant astrogliosis. A comprehensive cell atlas reanalysis of clinical specimens brings to light heightened clusterin (CLU) expression in a specific astrocyte subtype links to active lesions in MS patients. Our investigation reveals elevated astrocytic CLU levels in both active lesions of patient tissues and female murine MS models. CLU administration stimulates primary astrocyte proliferation while concurrently impedes astrocyte-mediated clearance of myelin debris. Intriguingly, CLU overload directly impedes OPCs differentiation and induces OPCs and OLs apoptosis. Mechanistically, CLU suppresses PI3K-AKT signaling in primary OPCs via very low-density lipoprotein receptor. Pharmacological activation of AKT rescues the damage inflicted by excess CLU on OPCs and ameliorates demyelination in the corpus callosum. Furthermore, conditional knockout of CLU emerges as a promising intervention, showcasing improved remyelination processes and reduced severity in murine MS models.
Project description:Astrocytes contribute to the pathogenesis of multiple sclerosis (MS); however, the mechanisms underlying the regulation of astrocytic responses remain unknown. Here we report an exhaustive molecular and functional characterization of astrocyte reactivity following exposure to cerebrospinal fluid (CSF) from MS patients classified according to the degree of inflammatory activity. We showed that mouse astrocytes exposed to CSF from patients with high inflammatory activity (MS-High) exhibited a specific pro-inflammatory reactive state that was characterized by enhanced NF-kB signalling. This reactive astrocyte state conferred a dysfunctional response through an altered pro-inflammatory secretome that drove neuronal dysfunction and impaired synaptic plasticity. SerpinE1 was identified as a potential downstream mediator of the non-cell-autonomous toxic effect on neuronal function based on its significant up-regulation in secretomes from astrocytes exposed to CSF from MS-high patients. Further, we identified chitinase 3-like 1 as a potential upstream modulator of astrocyte reactivity via activation of NF-kB signalling based on its significantly increased levels in the CSF from MS-High patients. Taken together our findings indicate that the inflammatory microenvironment in the central nervous system of MS patients can induce specific reactive astrocyte states that trigger neuronal degeneration and may ultimately contribute to disease progression.
Project description:Diverse subpopulations of astrocytes tile different brain regions to accommodate local requirements of neurons and associated neuronal circuits. Nevertheless, molecular mechanisms governing astrocyte diversity remain mostly unknown. We explored the role of a zinc finger transcription factor Yin Yang 1 (YY1) that is expressed in astrocytes. We found that specific deletion of YY1 from astrocytes causes severe motor deficits in mice, induces Bergmann gliosis, and results in simultaneous loss of GFAP expression in velate and fibrous cerebellar astrocytes. Single cell RNA-seq analysis showed that YY1 exerts specific effects on gene expression in subpopulations of cerebellar astrocytes. We found that although YY1 is dispensable for the initial stages of astrocyte development, it regulates subtype-specific gene expression during astrocyte maturation. Moreover, YY1 is continuously needed to maintain astrocyte identity in the adult cerebellum. Our findings suggest that YY1 plays critical roles regulating cerebellar astrocyte maturation during development and maintaining a mature phenotype of astrocytes in the adult cerebellum.
Project description:Chromosomes and genes are non-randomly arranged within the mammalian cell nucleus. Clustering of genes is of great significance in transcriptional regulation. However, the relevance of gene clustering in their expression during differentiation of neural precursor cells (NPCs) into astrocytes remains unclear. We performed a genome-wide enhanced circular chromosomal conformation capture (e4C) to screen genes associated with an astrocyte-specific gene, glial fibrillary acidic protein (Gfap), during astrocyte differentiation. We identified 13 genes that were specifically associated with Gfap and expressed in NPC-derived astrocytes. These results provide evidence for functional significance of gene clustering in transcriptional regulation during NPCs differentiation. comparison of NPCs vs LIF+ vs LIF- cells.