Microglia activation orchestrates CXCL10-mediated CD8+ T cell recruitment to promote aging-related white matter degeneration (fixed scRNA-seq)
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE283362 | GEO | 2025/03/07
REPOSITORIES: GEO
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Project description:Aging is the major risk factor for neurodegeneration and associated with structural and functional alterations in white matter. Myelin is particularly vulnerable to aging resulting in white matter-associated microglia activation. In this study, we employed pharmacological and genetic approaches to investigate microglial functions related to aging-associated changes in myelinated axons of mice. Our results reveal that maladaptive microglia activation promotes the accumulation of CD8+ T cells, leading to degeneration of myelinated axons and subsequent impairment of brain function and behavior. We characterize glial heterogeneity and aging-related changes in white matter by single-cell and spatial transcriptomics and reveal elaborate glial-immune interactions. Mechanistically, we show that the CXCL10-CXCR3 axis is crucial for the recruitment and retention of CD8+ T cells in aged white matter, where they exert pathogenic effects. Our results indicate that myelin-related microglia dysfunction promotes adaptive immune reactions in aging and identify putative targets to mitigate their detrimental impact.
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Project description:1. Aging is a major risk factor for the development of nervous system functional decline, even in the absence of diseases or trauma. The axon–myelin units and synaptic terminals are some of the neural structures most vulnerable to aging-related deterioration, but the underlying mechanisms are poorly understood. In the peripheral nervous system, macrophages—important representatives of the innate immune system—are prominent drivers of structural and functional decline of myelinated fibers and motor endplates during aging. Similarly, in the aging central nervous system (CNS), microglial cells promote damage of myelinated axons and synapses. Here we examine the role of cytotoxic CD8+ T lymphocytes, a type of adaptive immune cells previously identified as amplifiers of axonal perturbation in various models of genetically mediated CNS diseases but understudied in the aging CNS. We show that accumulation of CD8+ T cells drives axon degeneration in the normal aging mouse CNS and contributes to age-related cognitive and motor decline. We characterize CD8+ T-cell population heterogeneity in the adult and aged mouse brain by single-cell transcriptomics and identify aging-related changes. Mechanistically, we provide evidence that CD8+ T cells drive axon degeneration in a T-cell receptor- and granzyme B-dependent manner. Cytotoxic neural damage is further aggravated by systemic inflammation in aged but not adult mice. We also find increased densities of T cells in white matter autopsy material from older humans. Our results suggest that targeting CD8+ CNS-associated T cells in older adults might mitigate aging-related decline of brain structure and function. 2. Myelin defects lead to neurological dysfunction in various diseases and in normal aging. Chronic neuroinflammation often contributes to axon-myelin damage in these conditions and can be initiated and/or sustained by perturbed myelinating glia. We have previously shown that distinct mutations in the PLP1 gene result in neurodegeneration that is largely driven by adaptive immune cells. Here we characterize CD8+ CNS-associated T cells in these myelin mutants using single-cell transcriptomics and identify population heterogeneity and disease-associated changes. We demonstrate that early sphingosine-1-phosphate receptor modulation attenuates the recruitment of T cells and neural damage, while later targeting of CNS-associated T cell populations is inefficient and has no effect on neurodegeneration. Applying bone marrow chimerism and utilizing random X chromosome inactivation, we provide evidence that axonal damage is driven by cytotoxic, antigen specific CD8+ T cells that target mutant oligodendrocyte myelin. These findings offer insights into neural-immune interactions and are of translational relevance for neurological conditions associated with myelin defects and neuroinflammation.
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Project description:Two percent of all patients with X-linked intellectual disability (XLID) exhibit loss-of-function mutations in the palmitoylating enzyme, ZDHHC91,2. One of the main anatomical deficits observed in these patients is a decrease in corpus callosum volume and a disruption of white matter integrity. We demonstrated that ablation of Zdhhc9 in mice substantially impairs the maturation of ligodendrocytes, resulting in fewer mature, myelinating oligodendrocytes, higher numbers of oligodendrocyte progenitor cells and a decrease in the density of myelinated axons. Ultrastructural analysis of the remaining myelinated axons in the corpus callosum revealed further disruptions in myelin integrity. RNA sequencing and proteomic analyses revealed a concomitant decrease in the expression of genes and proteins involved in lipid metabolism, cholesterol synthesis and myelin compaction. These results reveal a previously underappreciated and fundamental role for ZDHHC9 and protein palmitoylation in regulating oligodendrocyte differentiation and myelinogenesis and provide mechanistic insights into the deficits observed in white matter volume in patients with mutations in ZDHHC9.
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