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Alzheimer's disease risk ABCA7 p.A696S variant disturbs the microglial response to amyloid pathology in mice

ABSTRACT: The adenosine triphosphate–binding cassette transporter A7 (ABCA7) gene is ranked as one of the top susceptibility loci for Alzheimer’s disease (AD). While ABCA7 mediates lipid transport across cellular membranes, ABCA7 loss of function has been shown to exacerbate amyloid-β (Aβ) pathology and compromise microglial function. Our family-based study uncovered an extremely rare ABCA7 p.A696S variant that was substantially segregated with the development of AD in 3 African American families. Using the knockin mouse model, we investigated the effects of ABCA7-A696S substitution on amyloid pathology and brain immune response in 5xFAD transgenic mice. Importantly, our study demonstrated that ABCA7-A696S substitution reduces amyloid plaque–associated microgliosis and increases dystrophic neurites around amyloid deposits compared to control mice. We also found increased X-34–positive amyloid plaque burden in 5xFAD mice with ABCA7-A696S substitution, while there was no evident difference in insoluble Aβ levels between mouse groups. Thus, ABCA7-A696S substitution may disrupt amyloid compaction resulting in aggravated neuritic dystrophy due to insufficient microglia barrier function. In addition, we observed that ABCA7-A696S substitution disturbs the induction of proinflammatory cytokines interleukin 1β and interferon γ in the brains of 5xFAD mice, although some disease-associated microglia gene expression, including Trem2 and Tyrobp, are upregulated. Lipidomics also detected higher total lysophosphatidylethanolamine levels in the brains of 5xFAD mice with ABCA7-A696S substitution than controls. These results suggest that ABCA7-A696S substitution might compromise the adequate innate immune response to amyloid pathology in AD by modulating brain lipid metabolism, providing novel insight into the pathogenic mechanisms mediated by ABCA7.

ORGANISM(S): Mus musculus

PROVIDER: GSE288170 | GEO | 2025/03/13

REPOSITORIES: GEO

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Project description:Alzheimer’s disease (AD) is an unremitting neurodegenerative disorder characterized by cerebral amyloid-β (Aβ) accumulation and gradual decline in cognitive function. Changes in brain energy metabolism arise in the preclinical phase of AD, suggesting an important metabolic component of early AD pathology. Neurons and astrocytes function in close metabolic collaboration, which is essential for the recycling of neurotransmitters in the synapse. However, how this metabolic interplay may be affected during the early stages of AD development has not been sufficiently investigated. Here, we provide an integrative analysis of cellular metabolism during the early stages of Aβ accumulation in the cerebral cortex and hippocampus of the 5xFAD mouse model of AD. Our electrophysiological examination revealed an increase in spontaneous excitatory signaling in hippocampal brain slices of 5xFAD mice. This hyperactive neuronal phenotype coincided with decreased hippocampal TCA cycle metabolism mapped by stable 13C isotope tracing. Particularly, reduced astrocyte TCA cycle activity led to decreased glutamine synthesis, in turn hampering neuronal GABA synthesis in the 5xFAD hippocampus. In contrast, cerebral cortical slices of 5xFAD mice displayed an elevated capacity for oxidative glucose metabolism suggesting a metabolic compensation. When we explored the brain proteome and metabolome of the 5xFAD mice, we found limited changes, supporting that the functional metabolic disturbances between neurons and astrocytes are early events in AD pathology. In addition, we show that synaptic mitochondrial and glycolytic function was impaired selectively in the 5xFAD hippocampus, whereas non-synaptic mitochondrial function was maintained. These findings were supported by ultrastructural analyses demonstrating disruptions in mitochondrial morphology, particularly in the 5xFAD hippocampus. Collectively, our study reveals complex region and cell specific metabolic adaptations, in the early stages of amyloid pathology, which may be fundamental for the progressing synaptic dysfunction in AD.

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Alzheimer's disease risk ABCA7 p.A696S variant disturbs the microglial response to amyloid pathology in mice

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