Project description:The Christchurch mutation (R136S) on the APOE3 (E3S/S) gene is associated with attenuation of tau load and cognitive decline despite the presence of a causal PSEN1 mutation and high levels of amyloid beta pathology in the carrier. However, the specific molecular mechanisms enabling the E3S/S mutation to mitigate tau-induced neurodegeneration remain unclear. Here, we replaced mouse ApoE with wild-type human E3 or E3S/S on a tauopathy background. The R136S mutation markedly decreased tau load and protected against tau-induced synaptic loss, myelin loss, and reduction in theta and gamma powers. Additionally, the R136S mutation reduced interferon response to tau pathology in both mouse and human microglia, suppressing cGAS-STING activation. Treating tauopathy mice carrying wild-type E3 with a cGAS inhibitor protected against tau-induced synaptic loss and induced similar transcriptomic alterations to those induced by the R136S mutation across brain cell types. Thus, suppression of microglial cGAS-STING-IFN pathway plays a central role in mediating the protective effects of R136S against tauopathy.
Project description:The Christchurch mutation (R136S) on the APOE3 (E3S/S) gene is associated with attenuation of tau load and cognitive decline despite the presence of a causal PSEN1 mutation and high levels of amyloid beta pathology in the carrier. However, the specific molecular mechanisms enabling the E3S/S mutation to mitigate tau-induced neurodegeneration remain unclear. Here, we replaced mouse ApoE with wild-type human E3 or E3S/S on a tauopathy background. The R136S mutation markedly decreased tau load and protected against tau-induced synaptic loss, myelin loss, and reduction in theta and gamma powers. Additionally, the R136S mutation reduced interferon response to tau pathology in both mouse and human microglia, suppressing cGAS-STING activation. Treating tauopathy mice carrying wild-type E3 with a cGAS inhibitor protected against tau-induced synaptic loss and induced similar transcriptomic alterations to those induced by the R136S mutation across brain cell types. Thus, suppression of microglial cGAS-STING-IFN pathway plays a central role in mediating the protective effects of R136S against tauopathy.
Project description:We describe in vivo follow-up PET imaging and postmortem findings from an autosomal dominant Alzheimer’s disease (ADAD) PSEN1 E280A carrier who was also homozygous for the APOE3 Christchurch (APOE3ch) variant and was protected against Alzheimer’s symptoms for almost three decades beyond the expected age of onset. We identified a distinct anatomical pattern of tau pathology with atypical accumulation in vivo and unusual postmortem regional distribution characterized by sparing in the frontal cortex and severe pathology in the occipital cortex. The frontal cortex and the hippocampus, less affected than the occipital cortex by tau pathology, contained Related Orphan Receptor B (RORB) positive neurons, homeostatic astrocytes and higher APOE expression. The occipital cortex, the only cortical region showing cerebral amyloid angiopathy (CAA), exhibited a distinctive chronic inflammatory microglial profile and lower APOE expression. Thus, the Christchurch variant impacts the distribution of tau pathology, modulates age at onset, severity, progression, and clinical presentation of ADAD, suggesting possible therapeutic strategies.
Project description:Alzheimer's Disease (AD) is the most prevalent neurodegenerative disorder characterized by extracellular amyloid plaque and neuronal tangle formation. A 2019 study discovered an association between the APOE3 Christchurch (APOE3Ch) variant and delayed AD progression in a PSEN1 mutation carrier. However, whether the APOE3Ch variant is causal to the delayed onset of AD and what is the underlying mechanism remains to be explored. In this study, we established neuron-microglia cocultures and neuroimmune organoids using CRISPR/Cas9-edited isogenic APOE3 and APOE3Ch microglia derived from human induced pluripotent stem cells (hiPSCs) along with PSEN1 mutant neurons or brain organoids. We show that APOE3Ch microglia exhibit enhanced phagocytic capacity and increased Tau clearance in neuron-microglia co-cultures. Moreover, APOE3Ch microglia were able to reduce phosphorylated Tau levels in PSEN1 mutant brain organoids. We also demonstrated that APOE3Ch microglia could preserve neural network activity in co-cultured PSEN1 neurons when challenged with synaptosomes prepared from AD patient brains. RNA-seq analysis identified phagocytosis and ferroptosis among pathways of differentially expressed genes from APOE3 and APOE3Ch microglia. Subsequent validation analyses established a causal link between reduced ferroptosis and enhanced phagocytosis including Tau clearance by APOE3Ch microglia, providing mechanistic insights into the neuroprotective role of APOE3Ch microglia. These findings together demonstrate that the APOE3Ch variant plays a causal role in microglial neuroprotection which can be exploited in therapeutic development for AD.
Project description:Apolipoprotein E4 (APOE4) is the strongest genetic risk factor for late-onset Alzheimer’s disease (LOAD), leading to earlier age of clinical onset and exacerbating pathologies. There is a critical need to identify protective targets. Recently, a rare APOE variant, APOE3-R136S (Christchurch), was found to protect against early-onset AD in a PSEN1-E280A carrier. We sought to determine if the R136S mutation also protects against APOE4-driven effects in LOAD. We generated tauopathy mouse and human iPSC-derived neuron models carrying human APOE4 with the homozygous or heterozygous R136S mutation. We found that the homozygous R136S mutation rescued APOE4-driven Tau pathology, neurodegeneration, and neuroinflammation. The heterozygous R136S mutation partially protected against APOE4-driven neurodegeneration and neuroinflammation, but not Tau pathology. Single-nucleus RNA-sequencing revealed that the APOE4-R136S mutation increased disease-protective and diminished disease-associated cell populations in a gene dose-dependent manner. Thus, the APOE-R136S mutation protects against APOE4-driven AD pathologies, providing a target for therapeutic development against AD.
Project description:Microbial infection, the strong trigger to directly induce inflammation in brain, is long considered a risk factor of Alzheimer's disease (AD), but how these infections contribute to neurodegeneration remains underexplored. To examine the effect of herpes simplex virus type 1 (HSV-1) infection on tauopathy in local hippocampus of P301S mice, we utilized a modified HSV-1 strain (mHSV-1) potentially relevant to AD, we found that its infection promotes tau-related pathology in part via activating neuroimmune cGAS-STING pathway in the tau mouse model. Specifically, Sting ablation causes the detectable improvement of neuronal dysfunction and loss in P301S mice, which is causally linked to lowered proinflammatory status in the brain. Administration of STING inhibitor H-151 alleviates neuroinflammation and tau-related pathology in P301S mice. These results jointly suggest that herpesviral infection, as the vital environmental risk factor, could induce tau-related pathology in AD pathogenesis partially via neuroinflammatory cGAS-STING pathway.
Project description:Microbial infection, the strong trigger to directly induce inflammation in brain, is long considered a risk factor of Alzheimer's disease (AD), but how these infections contribute to neurodegeneration remains underexplored. To examine the effect of herpes simplex virus type 1 (HSV-1) infection on tauopathy in local hippocampus of P301S mice, we utilized a modified HSV-1 strain (mHSV-1) potentially relevant to AD, we found that its infection promotes tau-related pathology in part via activating neuroimmune cGAS-STING pathway in the tau mouse model. Specifically, Sting ablation causes the detectable improvement of neuronal dysfunction and loss in P301S mice, which is causally linked to lowered proinflammatory status in the brain. Administration of STING inhibitor H-151 alleviates neuroinflammation and tau-related pathology in P301S mice. These results jointly suggest that herpesviral infection, as the vital environmental risk factor, could induce tau-related pathology in AD pathogenesis partially via neuroinflammatory cGAS-STING pathway.
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.
Project description:Sex is a key modifier of neurological disease outcomes. Microglia are implicated in neurological diseases and modulated by miRNAs, but it is unknown whether microglial miRNAs have sex-specific influences on disease. We show that microglial miRNA expression differs in males and females, and loss of miRNAs leads to sex-specific changes in the microglial transcriptome and to tau pathology. These findings suggest microglial miRNAs influence tau pathogenesis in a sex-specific manner.