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Loss of ATG7 in Microglia Impairs UPR, Triggers Ferroptosis and Weakens Amyloid Pathology Control [scRNA-seq]

ABSTRACT: Microglia impact brain development, homeostasis, and pathology. One important microglial function in Alzheimer’s Disease (AD) is to contain proteotoxic amyloid β (Aβ) plaques. Recent studies reported the involvement of autophagy-related (ATG) proteins in this process. Here we found that microglia-specific deletion of Atg7 in an AD mouse model impaired microglia coverage of Aβ plaques, increasing plaque diffusion and neurotoxicity. Single-cell RNA sequencing, biochemical and immunofluorescence analyses revealed that Atg7 deficiency reduces unfolded protein response (UPR) while increasing oxidative stress. Cellular assays demonstrated that these changes lead to lipoperoxidation and ferroptosis of microglia. In aged mice without Aβ build-up, UPR reduction and increase oxidative damage induced by Atg7 deletion did not impact microglia numbers. We conclude that reduced UPR and increased oxidative stress in Atg7-deficient microglia lead to ferroptosis when exposed to proteotoxic stress from Aβ plaques. However, these microglia can still manage misfolded protein accumulation as they age.

ORGANISM(S): Mus musculus

PROVIDER: GSE286094 | GEO | 2025/01/30

REPOSITORIES: GEO

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Loss of ATG7 in Microglia Impairs UPR, Triggers Ferroptosis and Weakens Amyloid Pathology Control [bulk RNA-seq]

Project description:Microglia impact brain development, homeostasis, and pathology. One important microglial function in Alzheimer’s Disease (AD) is to contain proteotoxic amyloid β (Aβ) plaques. Recent studies reported the involvement of autophagy-related (ATG) proteins in this process. Here we found that microglia-specific deletion of Atg7 in an AD mouse model impaired microglia coverage of Aβ plaques, increasing plaque diffusion and neurotoxicity. Single-cell RNA sequencing, biochemical and immunofluorescence analyses revealed that Atg7 deficiency reduces unfolded protein response (UPR) while increasing oxidative stress. Cellular assays demonstrated that these changes lead to lipoperoxidation and ferroptosis of microglia. In aged mice without Aβ build-up, UPR reduction and increase oxidative damage induced by Atg7 deletion did not impact microglia numbers. We conclude that reduced UPR and increased oxidative stress in Atg7-deficient microglia lead to ferroptosis when exposed to proteotoxic stress from Aβ plaques. However, these microglia can still manage misfolded protein accumulation as they age.

2025-01-30 | GSE286095 | GEO

TREM2 Drives Microglia Response to Amyloid-β via SYK-dependent and -independent Paths [SYK and TREM2 scRNA-seq]

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TREM2 Drives Microglia Response to Amyloid-β via SYK-dependent and -independent Paths [DAP12KI scRNA-seq]

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Project description:Aberrant increase of arachidonic acid (ARA) has long been implicated in the pathology of Alzheimer's disease (AD), while the underlying causal mechanism remains unclear. In this study, we revealed a link between ARA mobilization and microglial dysfunction in Aβ pathology. Lipidomic analysis of primary microglia from AppNL-GF mice showed a marked increase in free ARA and lysophospholipids (LPLs) along with a decrease in ARA-containing phospholipids, suggesting increased ARA release from phospholipids (PLs). To manipulate ARA-containing PLs in microglia, we genetically deleted Lysophosphatidylcholine Acyltransferase 3 (Lpcat3), the main enzyme catalyzing the incorporation of ARA into PLs. Loss of microglial Lpcat3 reduced the levels of ARA-containing phospholipids, free ARA and LPLs, leading to a compensatory increase in monounsaturated fatty acid (MUFA)-containing PLs in the AppNL-GF mice. Notably, the reduction of ARA in microglia significantly ameliorated oxidative stress and inflammatory responses while enhancing the phagocytosis of Aβ plaques and promoting the compaction of Aβ deposits. Mechanistically, sc-RNA seq suggested that LPCAT3 deficiency facilitates phagocytosis by facilitating de novo lipid synthesis while protecting microglia from oxidative damage. Collectively, our study reveals a novel mechanistic link between ARA mobilization and microglial dysfunction in AD. Lowering brain ARA levels through pharmacological or dietary interventions may be a potential therapeutic strategy to slow down AD progression.

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Project description:Microglia are involved in Alzheimer’s disease (AD) by adopting activated phenotypes. How ageing in the absence or presence of β-amyloid (Aβ) deposition in different brain areas affects this response and whether sex and AD risk genes are involved, remains however largely unknown. Here we analyzed the gene expression profiles of more than 10,000 individual microglia cells isolated from cortex and hippocampus of male and female AppNL-G-F at 4 different stages of Aβ deposition and in age-matched control mice. We demonstrate that microglia adopt two major activated states during normal aging and after exposure to amyloid plaques. One of the responses (activated response microglia, ARM) is enhanced in particular by amyloid plaques and is strongly enriched with AD risk genes. The ARM response is not homogeneous, as subgroups of microglia overexpressing MHC type II and tissue repair genes (Dkk2, Gpnmb, Spp1) are induced upon prolonged Aβ exposure. Microglia in female mice advance faster in the activation trajectories. Similar activated states were also found in a second AD model and in human brain. We demonstrate that abolishing the expression of Apoe, the major genetic risk factor for AD, impairs the establishment of ARMs, while the second microglia response type, enriched for interferon response genes, remains unaffected. Our data indicate that ARMs are the converging point of multiple AD risk factors.

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The major risk factors for Alzheimer’s disease: Age, Sex and Genes, modulate the microglia response to Aβ plaques (KW)

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Project description:ATG7 Loss in Microglia: Impaired UPR, Increased Oxidative Stress, Less Control of Amyloid Pathology

| PRJNA1203289 | ENA

TREM2 is a global regulator of microglia energetic and biosynthetic metabolism during steady state and in Alzheimer’s disease

Project description:The most common form of senile dementia, Alzheimer’s disease (AD), is characterized by Aβ plaques and neurofibrillary tangles in the CNS. AD genetic studies have identified high-risk hypomorphic variants in TREM2, a myeloid cell surface receptor that enables concerted microglial responses to Aβ plaques and neuronal cell death, including proliferation, survival, clustering and phagocytosis. How TREM2 promotes these responses is not known. Here, we demonstrate that TREM2 drives mTOR signaling, which maintains high ATP levels, supports biosynthetic pathways and suppresses AMPK phosphorylation and autophagy. In vitro, TREM2-deficient macrophages undergo dramatically increased autophagy and die in response to growth factor limitation or ER stress. Excessive autophagy is also evident in microglia from Trem2-/- 5XFAD mice and in post-mortem specimens from AD patients carrying TREM2 risk variants. Metabolic derailment, autophagy and cell death can be circumvented by engaging alternative energy production pathways. Thus, restoring microglial energetic and anabolic levels may be a future therapeutic avenue for TREM2-associated neurological disease.

2017-08-15 | GSE98563 | GEO

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Project description:Microglia, the innate immune cells of the central nervous system, perform critical inflammatory and non-inflammatory functions to maintain homeostasis and normal neural function. However in Alzheimer’s disease (AD), these beneficial functions become progressively impaired, contributing to synapse and neuron loss and cognitive impairment. The inflammatory cyclooxygenase-PGE2 pathway, including the PGE2 receptor EP2, is implicated in AD development, both in human epidemiology and in transgenic models of AD. To test the transcriptional responses of EP2-deficient microglia to Aβ in vivo, we used mice in which the EP2 receptor is conditionally deleted in microglia using the CD11b-Cre transgene and floxed alleles of the EP2 gene. By injecting these mice with Aβ ICV and isolating microglia from the brains, we have been able to establish the transcriptional response of microglia to Aβ in vivo and test how EP2 deletion in microglia affects this response. 8 month-old C57BL/6 mice, of the genotype CD11b-Cre; EP2+/+ or CD11b-Cre; EP2lox/lox, were injected I.C.V. with either Aβ or vehicle. 48 hours after injection, the mice were sacrificed and transcardially perfused with cold heparinized 0.9% NaCl. Brains were then removed from the mice and pooled, two brains of the same genotype per sample, to ensure adequate cell and RNA yield. The brains were then enzymatically dissociated for microglia isolation using the Neural Tissue Dissociation Kit (P), MACS Separation Columns (LS), and magnetic CD11b Microbeads from Miltenyi Biotec according to the manufacturer's protocol. Immediately after isolating the microglia, RNA was extracted from the cells for microarray analysis.

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