Plaque-induced transcriptional reprogramming of microglia towards lymphoid receptor expression protects against Alzheimer's disease [scRNA-seq]
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE296768 | GEO | 2025/08/07
REPOSITORIES: GEO
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Project description:Microglia, the innate immune cells of the brain, play a defining role in the progression of Alzheimer’s disease (AD). The microglial response to amyloid plaques can be either neuroprotective or neurotoxic. Here we show that the protective function of microglia is associated with and functionally linked to a transcriptional shift toward lymphoid gene expression. Microglial contact with the plaques induces downregulation of PU.1, a lineage-specifying transcription factor. PU.1 downregulation plays a key role in mitigating the severity of AD, as evidenced by a reduction in neurotoxic microglia activation, preservation of neuronal connections, maintenance of cognitive function, and increased survival in mice with genetically reduced PU.1 expression in microglia. The neuroprotective effect of PU.1 downregulation is linked to the de-repression of lymphoid-specific proteins, particularly CD28—a surface protein critical for T cell activation. Microglia-specific deficiency in CD28, which is expressed exclusively in a small subset of plaque-associated PU.1low microglia, promotes an inflammatory microglial state and associated increase in amyloid plaque load. Our findings suggest that PU.1low lymphoid/CD28-expressing microglia that emerge in response to AD pathology exert a suppressive, anti-inflammatory effect during AD. This novel role of CD28 -and potentially other lymphoid co-stimulatory or co-inhibitory receptor proteins- in governing microglia responses in AD points to possible new immunotherapy approaches for AD treatment.
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Project description:Microglia, the innate immune cells of the brain, play a defining role in the progression of Alzheimer’s disease (AD). The microglial response to amyloid plaques can be either neuroprotective or neurotoxic. Here we show that the protective function of microglia is associated with and functionally linked to a transcriptional shift toward lymphoid gene expression. Microglial contact with the plaques induces downregulation of PU.1, a lineage-specifying transcription factor. PU.1 downregulation plays a key role in mitigating the severity of AD, as evidenced by a reduction in neurotoxic microglia activation, preservation of neuronal connections, maintenance of cognitive function, and increased survival in mice with genetically reduced PU.1 expression in microglia. The neuroprotective effect of PU.1 downregulation is linked to the de-repression of lymphoid-specific proteins, particularly CD28—a surface protein critical for T cell activation. Microglia-specific deficiency in CD28, which is expressed exclusively in a small subset of plaque-associated PU.1low microglia, promotes an inflammatory microglial state and associated increase in amyloid plaque load. Our findings suggest that PU.1low lymphoid/CD28-expressing microglia that emerge in response to AD pathology exert a suppressive, anti-inflammatory effect during AD. This novel role of CD28 -and potentially other lymphoid co-stimulatory or co-inhibitory receptor proteins- in governing microglia responses in AD points to possible new immunotherapy approaches for AD treatment.
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Project description:Microglia, the innate immune cells of the brain, play a defining role in the progression of Alzheimer’s disease (AD). The microglial response to amyloid plaques can be either neuroprotective or neurotoxic. Here we show that the protective function of microglia is associated with and functionally linked to a transcriptional shift toward lymphoid gene expression. Microglial contact with the plaques induces downregulation of PU.1, a lineage-specifying transcription factor. PU.1 downregulation plays a key role in mitigating the severity of AD, as evidenced by a reduction in neurotoxic microglia activation, preservation of neuronal connections, maintenance of cognitive function, and increased survival in mice with genetically reduced PU.1 expression in microglia. The neuroprotective effect of PU.1 downregulation is linked to the de-repression of lymphoid-specific proteins, particularly CD28—a surface protein critical for T cell activation. Microglia-specific deficiency in CD28, which is expressed exclusively in a small subset of plaque-associated PU.1low microglia, promotes an inflammatory microglial state and associated increase in amyloid plaque load. Our findings suggest that PU.1low lymphoid/CD28-expressing microglia that emerge in response to AD pathology exert a suppressive, anti-inflammatory effect during AD. This novel role of CD28 -and potentially other lymphoid co-stimulatory or co-inhibitory receptor proteins- in governing microglia responses in AD points to possible new immunotherapy approaches for AD treatment.
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Project description:Microglia, the innate immune cells of the brain, play a defining role in the progression of Alzheimer’s disease (AD). The microglial response to amyloid plaques can be either neuroprotective or neurotoxic. Here we show that the protective function of microglia is associated with and functionally linked to a transcriptional shift toward lymphoid gene expression. Microglial contact with the plaques induces downregulation of PU.1, a lineage-specifying transcription factor. PU.1 downregulation plays a key role in mitigating the severity of AD, as evidenced by a reduction in neurotoxic microglia activation, preservation of neuronal connections, maintenance of cognitive function, and increased survival in mice with genetically reduced PU.1 expression in microglia. The neuroprotective effect of PU.1 downregulation is linked to the de-repression of lymphoid-specific proteins, particularly CD28—a surface protein critical for T cell activation. Microglia-specific deficiency in CD28, which is expressed exclusively in a small subset of plaque-associated PU.1low microglia, promotes an inflammatory microglial state and associated increase in amyloid plaque load. Our findings suggest that PU.1low lymphoid/CD28-expressing microglia that emerge in response to AD pathology exert a suppressive, anti-inflammatory effect during AD. This novel role of CD28 -and potentially other lymphoid co-stimulatory or co-inhibitory receptor proteins- in governing microglia responses in AD points to possible new immunotherapy approaches for AD treatment.
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Project description:Alzheimer's disease (AD) is characterized by a sequential progression of amyloid plaques (A), neurofibrillary tangles (T) and neurodegeneration (N), constituting ATN pathology. While microglia are considered key contributors to AD pathogenesis, their contribution in the combined presence of ATN pathologies remains incompletely understood. As sensors of the brain microenvironment, microglial phenotypes and contributions are importantly defined by the pathologies in the brain, indicating the need for their analysis in preclinical models that recapitulate combined ATN pathologies, besides their role in A and T models only. Here, we report a new tau-seed model in which amyloid pathology facilitates bilateral tau propagation associated with brain atrophy, thereby recapitulating robust ATN pathology. Single-cell RNA sequencing revealed that ATN pathology exacerbated microglial activation towards disease-associated microglia (DAM) states, with a significant upregulation of Apoe as compared to amyloid-only models (A). Importantly, Colony-Stimulating Factor 1 Receptor inhibition preferentially eliminated non-plaque-associated versus plaque associated microglia. The preferential depletion of non-plaque-associated microglia significantly attenuated tau pathology and neuronal atrophy, indicating their detrimental role during ATN progression. Together, our data reveal the intricacies of microglial activation and their contributions to pathology in a model that recapitulates the combined ATN pathologies of Alzheimer's disease. Our data may provide a basis for microglia-targeting therapies selectively targeting detrimental microglial populations, while conserving protective populations.
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Project description:Neuroinflammation is thought to contribute to the pathogenesis of Alzheimer’s disease (AD), yet numerous studies have demonstrated a beneficial role for neuroinflammation in amyloid plaque clearance. We have previously shown that sustained expression of IL-1β in the hippocampus of APP/PS1 mice decreases amyloid plaque burden independent of recruited CCR2+ myeloid cells, suggesting resident microglia as the main phagocytic effectors of IL-1β-induced plaque clearance. To date, however, the mechanisms of IL-1β-induced plaque clearance remain poorly understood. To determine whether IL-1β-induced plaque clearance is due to enhanced microglial phagocytosis of Aβ, APP/PS1 mice induced to express mature human IL-1β in the hippocampus via adenoviral transduction were treated with the Aβ fluorescent probe methoxy-X04 (MX04) and microglial internalization of Aβ was analyzed by flow cytometry and immunohistochemistry. We found that resident microglia (CD45loCD11b+) constituted >70% of the MX04+ cells in both control and IL-1β-treated conditions, and that <10% of MX04+ cells were recruited myeloid cells (CD45hiCD11b+). However, we found that IL-1β treatment did not augment the percentage of MX04+ microglia nor the quantity of Aβ internalized by individual microglia. Instead, we found that IL-1β treatment resulted in a significant increase in the total number of MX04+ microglia in the hippocampus due to IL-1β-induced proliferation. Consistent with these results, transcriptomic analyses revealed very similar gene expression profiles between MX04+ and MX04- microglia, indicating IL-1β does not drive enhanced expression of phagocytosis-related genes. By contrast, IL-1β treatment was associated with large-scale changes in the expression of genes related to proliferation, immune function and inflammation. Together, these studies demonstrate that IL-1β induces microglial proliferation and the expression of genes involved in inflammatory immune functions that may be related to Aβ clearance.
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