Spatial Transcriptomics and In Situ Sequencing to Study Alzheimer’s Disease
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ABSTRACT: While complex inflammatory-like alterations are observed around the amyloid plaques of Alzheimer disease (AD), little is known about the molecular changes and cellular interactions that characterize this response. We investigate here in an AD mouse model the transcriptional changes occurring in tissue domains of 100 μm diameter around the amyloid plaques using spatial transcriptomics. We demonstrate early alterations in a gene co-expression network enriched for myelin and oligodendrocyte genes (OLIG), while a multicellular gene co- expression network of Plaque-Induced Genes (PIGs) involving the complement system, oxidative stress, lysosomes and inflammation is prominent in the later phase of the disease. We confirm the majority of the observed alterations at the cellular level using in situ sequencing on mouse and human brain sections. Genome-wide spatial transcriptomic analysis provides an unprecedented approach to untangle the dysregulated cellular network in the vicinity of pathogenic hallmarks of AD and other brain diseases.
Project description:In this study, we characterize the transcriptomic alterations, cellular compositions, and signaling perturbations in the amyloid plaque niche in an AD mouse model using high-resolution spatial transcriptomics (CosMx and Stereo-seq). We discover a wide heterogeneity in the cellular composition of amyloid plaque niches, marked by an increase in microglial accumulation over time. We profile the alterations of glial cells as they are exposed to plaques, and conclude that the microglial response to plaques is consistent across different brain regions, while the astrocytic response is more heterogeneous. In turn, as the microglial density of plaque niches increases, astrocytes acquire a more neurotoxic phenotype and play a key role in inducing GABAergic signaling and decreasing glutamatergic signaling in neurons of the hippocampus. Taken together, we show that astrocytic signaling around plaque pathology is disrupted with increasing microglial density, which in turn induces an imbalance in synaptic signaling in neurons in the hippocampus.
Project description:In this study, we characterize the transcriptomic alterations, cellular compositions, and signaling perturbations in the amyloid plaque niche in an AD mouse model using high-resolution spatial transcriptomics (CosMx and Stereo-seq). We discover a wide heterogeneity in the cellular composition of amyloid plaque niches, marked by an increase in microglial accumulation over time. We profile the alterations of glial cells as they are exposed to plaques, and conclude that the microglial response to plaques is consistent across different brain regions, while the astrocytic response is more heterogeneous. In turn, as the microglial density of plaque niches increases, astrocytes acquire a more neurotoxic phenotype and play a key role in inducing GABAergic signaling and decreasing glutamatergic signaling in neurons of the hippocampus. Taken together, we show that astrocytic signaling around plaque pathology is disrupted with increasing microglial density, which in turn induces an imbalance in synaptic signaling in neurons in the hippocampus.
Project description:Peripheral inflammation has been associated with various neurodegeneration, including Alzheimer's Disease (AD). In this study, we employed an AD mouse model nasally infected with Staphylococcus aureus to assess the impact of chronic or acute peripheral inflammation on brain transcriptome and amyloid pathology. The chronic exposure increased the diffuse and compact amyloid plaques and blood cytokine levels. Following a short-term exposure, single-cell and spatial transcriptomics uncovered cell type- and spatial-specific transcriptional changes indicating a dysregulation of the brain barriers, including the blood-brain and the blood-cerebrospinal fluid barriers. Brain macrophages exhibited increased Apoe expression and macrophage-specific genes were upregulated at ventricular areas of infected mice. In addition, we report an increase of disease associated microglia genes around the A plaques, together with disbalances in neuronal expression in response to peripheral inflammation. Overall, results enlighten the mechanisms linking peripheral inflammation to AD.
Project description:Peripheral inflammation has been associated with various neurodegeneration, including Alzheimer's Disease (AD). In this study, we employed an AD mouse model nasally infected with Staphylococcus aureus to assess the impact of chronic or acute peripheral inflammation on brain transcriptome and amyloid pathology. The chronic exposure increased the diffuse and compact amyloid plaques and blood cytokine levels. Following a short-term exposure, single-cell and spatial transcriptomics uncovered cell type- and spatial-specific transcriptional changes indicating a dysregulation of the brain barriers, including the blood-brain and the blood-cerebrospinal fluid barriers. Brain macrophages exhibited increased Apoe expression and macrophage-specific genes were upregulated at ventricular areas of infected mice. In addition, we report an increase of disease associated microglia genes around the A plaques, together with disbalances in neuronal expression in response to peripheral inflammation. Overall, results enlighten the mechanisms linking peripheral inflammation to AD.
Project description:Peripheral inflammation has been associated with various neurodegeneration, including Alzheimer's Disease (AD). In this study, we employed an AD mouse model nasally infected with Staphylococcus aureus to assess the impact of chronic or acute peripheral inflammation on brain transcriptome and amyloid pathology. The chronic exposure increased the diffuse and compact amyloid plaques and blood cytokine levels. Following a short-term exposure, single-cell and spatial transcriptomics uncovered cell type- and spatial-specific transcriptional changes indicating a dysregulation of the brain barriers, including the blood-brain and the blood-cerebrospinal fluid barriers. Brain macrophages exhibited increased Apoe expression and macrophage-specific genes were upregulated at ventricular areas of infected mice. In addition, we report an increase of disease associated microglia genes around the A plaques, together with disbalances in neuronal expression in response to peripheral inflammation. Overall, results enlighten the mechanisms linking peripheral inflammation to AD.
Project description:We found some novel miRNA that targets SIRT1 may contribute to the pathogenesis in AD mouse model. We first identified that SIRT1 is significantly reduced in Alzheimer patient`s precentral gyrus and 5XFAD mice. To determine whether the strategy of inhibiting some miRNA affects AD pathology, we synthesized antisense oligonucleotides of miRNA (miRNA ASO) and studied this sequence in the brain of 5XFAD through direct intracerebral ventricular injection using stereotaxic instrument. We identified miRNA ASO significantly reduced amyloid beta plaque and amyloid production enzyme. Importantly, the attenuation of amyloid beta plaques through miRNA ASO was caused by a phagocytic activity of glial cells, by which it can directly target CD36. miRNA ASO also decreases inflammatory responses. These results inhibit neuronal loss caused by amyloid beta and leading to improvement of cognitive impairment. These insights of miRNA ASO suggests as therapeutic scope against AD pathology.
Project description:Microglial dysfunction is a key pathological feature of Alzheimer´s disease (AD), but little is known about proteome-wide changes in microglia during the course of AD pathogenesis and their consequences for microglial function. Here, we performed an in-depth proteomic characterization of microglia in two AD mouse models, the overexpression APPPS1 and the knock-in AppNL-G-F (APP-KI) model. Proteome changes were followed from pre-deposition to early, middle and advanced stages of amyloid plaque pathology, revealing a large panel of Microglial Amyloid Response Proteins (MARPs) that reflect a heterogeneity of microglial alterations triggered by Adeposition. We demonstrate that the occurrence of MARPs coincided with the deposition of fibrillar A, recruitment of microglia to amyloid plaques and phagocytic dysfunction. While the proteomic and functional microglial changes were already markedly seen in 3 months old APPPS1 mice, they were delayed in the APP-KI model that generates substantially less fibrillar A. The identified microglial proteomic fingerprints of AD provide a valuable resource for functional studies of novel molecular targets and potential biomarkers for monitoring AD progression or therapeutic efficacy.
Project description: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:The amyloid precursor protein (APP) plays a central role in the pathogenesis of Alzheimerâ??s disease (AD). Processing of APP by β- and γ-secretase activities results in the production of Ã?-amyloid (AÃ?), the main constituent of Alzheimer plaques, but also in the generation of the APP intracellular domain (AICD). Recently, it has been demonstrated that AICD has transactivation potential, however, the targets of AICD dependent gene regulation and hence the physiological role of AICD remain largely unknown. In this work we analysed transcriptome changes during AICD dependent gene regulation using a human neural cell culture system inducible for expression of AICD, its co-activator Fe65, or the combination of both. Induction of AICD was associated with increased expression of genes with known function in the organization and dynamics of the actin cytoskeleton as well as genes involved in the regulation of apoptosis.
Project description:Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder that is influenced by genetic and environmental risk factors, such as inheritance of ε4 allele of APOE (APOE4), sex and diet. Here, we examined the effect of high fat diet (HFD) on amyloid pathology and expression profile in brains of AD model mice expressing human APOE isoforms (APP/E3 and APP/E4 mice). APP/E3 and APP/E4 mice were fed HFD or Normal diet for 3 months. We found that HFD significantly increased amyloid plaques in male and female APP/E4, but not in APP/E3 mice. To identify differentially expressed genes and gene-networks correlated to diet, APOE isoform and sex, we performed RNA sequencing and applied Weighted Gene Co-expression Network Analysis. We determined that the immune response network with major hubs Tyrobp/DAP12, Csf1r, Tlr2, C1qc and Laptm5 correlated significantly and positively to the phenotype of female APP/E4-HFD mice. Correspondingly, we found that in female APP/E4-HFD mice, microglia coverage around plaques, particularly of larger size, was significantly reduced. This suggests altered containment of the plaque growth and sex-dependent vulnerability in response to diet. The results of our study show concurrent impact of diet, APOE isoform and sex on the brain transcriptome and AD-like phenotype.