Distinct transcriptomic responses to Ab plaques, neurofibrillary tangles, and APOE in Alzheimer’s disease
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ABSTRACT: INTRODUCTION: Omics studies have revealed that various brain cell types undergo profound molecular changes in Alzheimer’s disease (AD) but the spatial relationships with plaques and tangles and APOE-linked differences remain unclear. METHODS: We performed laser capture microdissection of Ab plaques, the 50mm halo around them, tangles with the 50mm halo around them, and areas distant (>50mm) from plaques and tangles in the temporal cortex of AD and control donors, followed by RNA-sequencing. RESULTS: Ab plaques exhibited upregulated microglial (neuroinflammation) and downregulated neuronal (neurotransmission/energy metabolism) genes, whereas tangles had mostly downregulated neuronal genes. Ab plaques had more differentially expressed genes than tangles. We identified a gradient Ab plaque>peri-plaque>tangle>distant for these changes. AD APOEe4 homozygotes had greater changes than APOEe3 across locations, especially within Ab plaques. DISCUSSION: Transcriptomic changes in AD consist primarily of neuroinflammation and neuronal dysfunction, are spatially associated mainly with Ab plaques, and are exacerbated by the APOEe4 allele.
Project description:Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid-beta (Ab) plaques and neurofibrillary tangles, neuroinflammation, and glial activation. Asrij/OCIAD1 (Ovarian Carcinoma Immunoreactive Antigen Domain containing protein 1) is an AD-associated factor. Increased Asrij levels in the brains of AD patients and mouse models are linked to the severity of neurodegeneration. However, the contribution of Asrij to AD progression and whether reducing Asrij levels is sufficient to mitigate Ab pathology in vivo is unclear. To explore the impact of Asrij on AD pathology, we deleted asrij in the APP/PS1 mouse model of AD and analyzed the effects on AD hallmarks. We find that Asrij depletion ameliorates cognitive impairments, Ab deposition, neuronal and synaptic damage, and reactive astrogliosis in the AD mouse. Emerging evidence indicates a critical role of microglia in influencing AD pathology. Notably, Asrij-deficient microglia exhibit reduced plaque-associated proliferation and decreased phagocytic activity. Transcriptomic analyses of AD microglia reveal upregulation of energy metabolism pathways and downregulation of innate immunity and inflammatory pathways upon Asrij depletion. Mechanistically, loss of Asrij increases mitochondrial activity and Akt/mTOR signaling and impedes the pro-inflammatory Disease-Associated Microglia (DAM) state. Reduced levels of pro-inflammatory cytokines and decreased STAT3 and NF-kB activation indicate protective changes in AD microglia. Taken together, our results suggest that increased Asrij levels reported in AD, may suppress microglial metabolic activity and promote inflammatory microglial activation, thereby exacerbating AD pathology. Our study establishes a novel role for Asrij in regulating microglial responses to Ab pathology, and could be a potential target for therapeutic intervention.
Project description:A typical pathological feature of Alzheimer’s disease (AD) is the appearance in the brain of senile plaques made up of B-amyloid (AB) and neurofibrillary tangles. Ad is also associated with an abnormal accumulation of some metal ions and we have recently shown that one of these, aluminum (Al), plays a relevant role in affecting AB aggregation and neurotoxicity. In this study, employing a microarray analysis of 29,166 genes, we investigated the effects induced by the exposure to the AB-Al complex on the gene expression profile of a cell line of neuronal-like cells, the SH-SY5Y. Results from the microarray essay indicate that, compared to AB or Al alone, exposure to AB-Al produced selective changes in gene expression. Some of the genes selectively over or under expressed are directly related to AD.
Project description:Sterile neuroinflammation initiated by damage-associated molecular patterns (DAMPs) has been regarded as an important driver in Alzheimer's disease (AD) and can occur prior or independently of the deposition of extracellular amyloid-β (Aβ) plaques and intracellular tau neurofibrillary tangles (NFTs). Genetic ablation or pharmacological inhibition of GPR34 reduced microglia activation, Aβ deposition and cognition impairment. Moreover, GPR34 inhibition prevented aging associated neuroinflammation and cognition impairment without the presence of Aβ plaques.
Project description:Late-onset Alzheimer’s disease (LOAD) is the most common form of AD. However, modeling sporadic LOAD, without clear genetic predispositions, to capture hallmark neuronal pathologies such as extracellular amyloid-β (Aβ) plaque deposition, intracellular tau tangles, and neuronal loss, remains an unmet need. Here, we demonstrate that neurons generated by microRNA-based direct reprogramming of fibroblasts from patients affected by autosomal dominant AD (ADAD) and LOAD in a three-dimensional (3D) environment, effectively recapitulate key neuropathological features of AD without additional cellular or genetic insults. These LOAD neurons exhibit Aβ-dependent neurodegeneration, as treatment with β- or γ-secretase inhibitors before (but not subsequent to) Aβ deposit formation mitigated neuronal death. Moreover, inhibiting age-associated retrotransposable elements (RTEs) in LOAD neurons reduced both Ab deposition and neurodegeneration. Our study underscores the efficacy of modeling late-onset neuropathology of LOAD through high-efficiency microRNA-based neuronal reprogramming.
Project description:Late-onset Alzheimer’s disease (LOAD) is the most common form of AD. However, modeling sporadic LOAD, without clear genetic predispositions, to capture hallmark neuronal pathologies such as extracellular amyloid-β (Aβ) plaque deposition, intracellular tau tangles, and neuronal loss, remains an unmet need. Here, we demonstrate that neurons generated by microRNA-based direct reprogramming of fibroblasts from patients affected by autosomal dominant AD (ADAD) and LOAD in a three-dimensional (3D) environment, effectively recapitulate key neuropathological features of AD without additional cellular or genetic insults. These LOAD neurons exhibit Aβ-dependent neurodegeneration, as treatment with β- or γ-secretase inhibitors before (but not subsequent to) Aβ deposit formation mitigated neuronal death. Moreover, inhibiting age-associated retrotransposable elements (RTEs) in LOAD neurons reduced both Ab deposition and neurodegeneration. Our study underscores the efficacy of modeling late-onset neuropathology of LOAD through high-efficiency microRNA-based neuronal reprogramming.
Project description:Late-onset Alzheimer’s disease (LOAD) is the most common form of AD. However, modeling sporadic LOAD, without clear genetic predispositions, to capture hallmark neuronal pathologies such as extracellular amyloid-β (Aβ) plaque deposition, intracellular tau tangles, and neuronal loss, remains an unmet need. Here, we demonstrate that neurons generated by microRNA-based direct reprogramming of fibroblasts from patients affected by autosomal dominant AD (ADAD) and LOAD in a three-dimensional (3D) environment, effectively recapitulate key neuropathological features of AD without additional cellular or genetic insults. These LOAD neurons exhibit Aβ-dependent neurodegeneration, as treatment with β- or γ-secretase inhibitors before (but not subsequent to) Aβ deposit formation mitigated neuronal death. Moreover, inhibiting age-associated retrotransposable elements (RTEs) in LOAD neurons reduced both Ab deposition and neurodegeneration. Our study underscores the efficacy of modeling late-onset neuropathology of LOAD through high-efficiency microRNA-based neuronal reprogramming.
Project description:Neuroinflammation is one of the major neuropathological hallmarks of Alzheimer's disease (AD) and related tauopathies. Activated microglia often co-exist in the same brain regions where tau protein accumulates as hyperphosphorylated and aggregated PHFs or neurofibrillary tangles (NFTs) within neurons in patients with AD and related tauopathies. However, the exact mechanisms how pathological tau could induce neuroinflammatory responses are not clear. In this study, we treated primary human microglia with purified human PHFs and performed RNA-sequence analysis.
Project description:Alzheimer’s disease (AD) is characterized by neuroinflammation, accumulation of amyloid-β (Aβ) plaques and neuronal degeneration in the brain. The APOE4 variant of apolipoprotein E (apoE) is the most prevalent genetic risk allele associated with late-onset AD. ApoE interacts with complement regulator factor H (FH) but the role of this interaction in AD pathogenesis is unknown.
Project description:We investigated spatiotemporal molecular patterns related to AD pathophsiology using spatially resolved transcriptome of the AD mouse model. The late change of gray matters of AD was commonly related to neuroinflammation, while the early change in the white matter of AD represented neuronal projection and ensheathment of axons before the amyloid plaques accumulation. Disease-associated microglia and astrocyte signatures were spatially differently enriched. Our results provide a key spatiotemporally heterogeneous molecular change particularly related to inflammation in AD.
Project description:Alzheimer’s disease (AD) is the most prevalent neurodegenerative disease and the most common form of dementia. AD is characterized by progressive memory loss and cognitive decline, affecting behavior, speech, and motor abilities. The neuropathology of AD includes the formation of extracellular amyloid-β plaques and intracellular neurofibrillary tangles of phosphorylated tau, as well as neuronal loss. Although neuronal loss is a primary hallmark of AD, non-neuronal cell populations are known to maintain brain homeostasis and neuronal health through neuron-glia and glial cell crosstalk via chemical messengers. To investigate altered glia-neuron communication in the presence of amyloid-β and tau pathology, we generated snRNA-seq data from the hippocampus of 3xTg-AD mice at 6 and 12 months and age-matched wild-type littermates. We predicted altered glia-neuron interactions between senders (astrocytes, microglia, oligodendrocytes, and OPCs) and receivers (excitatory and inhibitory neurons) across time points. We further investigated these interactions through pseudo-bulk differential expression, functional enrichment, and gene regulatory analyses.