Project description:Despite diverging levels of amyloid-β (Aβ) and TAU pathology, different mouse models, as well as sporadic AD patients show predictable patterns of episodic memory loss. MiRNA deregulation is well established in AD brain but it is unclear whether Aβ or Tau pathology drives those alterations and whether miRNA changes contribute to cognitive decline. Therefore miRNAseq was performed on the hippocampus of APPswe/PS1L166P and Thy-TAU22 mice and their respective wild-type littermates when they were cognitively intact (4 months) and impaired (10 months). We found 6 miRNAs that are commonly upregulated between APPtg and TAUtg mice, and four of these were also altered in AD patients. All 6 miRNAs are strongly enriched in neurons as verified by in situ hybridization.
Project description:BACKGROUND:Despite diverging levels of amyloid-β (Aβ) and TAU pathology, different mouse models, as well as sporadic AD patients show predictable patterns of episodic memory loss. MicroRNA (miRNA) deregulation is well established in AD brain but it is unclear whether Aβ or TAU pathology drives those alterations and whether miRNA changes contribute to cognitive decline. METHODS:miRNAseq was performed on cognitively intact (4 months) and impaired (10 months) male APPtg (APPswe/PS1L166P) and TAUtg (THY-Tau22) mice and their wild-type littermates (APPwt and TAUwt). We analyzed the hippocampi of 12 mice per experimental group (n = 96 in total), and employed a 2-way linear model to extract differentially expressed miRNAs. Results were confirmed by qPCR in a separate cohort of 4 M and 10 M APPtg and APPwt mice (n = 7-9 per group) and in human sporadic AD and non-demented control brain. Fluorescent in situ hybridization identified their cellular expression. Functional annotation of predicted targets was performed using GO enrichment. Behavior of wild-type mice was assessed after intracerebroventricular infusion of miRNA mimics. RESULTS:Six miRNAs (miR-10a-5p, miR-142a-5p, miR-146a-5p, miR-155-5p, miR-211-5p, miR-455-5p) are commonly upregulated between APPtg and TAUtg mice, and four of these (miR-142a-5p, miR-146a-5p, miR-155-5p and miR-455-5p) are altered in AD patients. All 6 miRNAs are strongly enriched in neurons. Upregulating these miRNAs in wild-type mice is however not causing AD-related cognitive disturbances. CONCLUSION:Diverging AD-related neuropathologies induce common disturbances in the expression of neuronal miRNAs. 4 of these miRNAs are also upregulated in AD patients. Therefore these 4 miRNAs (miR-142a-5p, miR-146a-5p, miR-155-5p and miR-455-5p) appear part of a core pathological process in AD patients and APPtg and TAUtg mice. They are however not causing cognitive disturbances in wild-type mice. As some of these miRNA target AD relevant proteins, they may be, in contrast, part of a protective response in AD.
Project description:Alzheimer’s disease (AD) is the most prevalent form of dementia and is characterized by abnormal extracellular aggregates of amyloid-b and intraneuronal hyperphosphorylated, tau tangles and neuropil threads. Microglia, the tissue-resident macrophages of the central nervous system (CNS), are important for CNS homeostasis and implicated in AD pathology. In amyloid mouse models, a phagocytic/activated microglia phenotype has been identified. How increasing levels of amyloid-b and tau pathology affect human microglia transcriptional profiles is unknown. Here, we performed snRNAseq on 482,472 nuclei from non-demented control brains and AD brains containing only amyloid-b plaques or both amyloid-b plaques and tau pathology. Within the microglia population, distinct expression profiles were identified of which two were AD pathology-associated. The phagocytic/activated AD1-microglia population abundance strongly correlated with tissue amyloid-b load and localized to amyloid-b plaques. The AD2-microglia abundance strongly correlated with tissue phospho-tau load and these microglia were more abundant in samples with over tau pathology. This full characterization of human disease associated microglia phenotypes provides new insights in the pathophysiological role of microglia in AD and offers new targets for microglia-state-specific therapeutic strategies.
Project description:The purpose of this project was to compare whole genome expression in 5 transgenic mice with human genes for dementia that result in either plaques or tangle pathology to the expression in wild-type control mice and to each other at different stages of disease progression. Total RNA was obtained from hippocampus, cortex and cerebellum in four lines of ‘amyloid’ transgenic mice (mutant human APP and APP/PSEN1 genes) and ‘TAU’ transgenic mice (mutant human MAPT gene) as well as wild-type control mice at 8,16, 32 and 72 weeks
Project description:Polygenic risk scores have identified that genetic variants without genome-wide significance still add to the genetic risk of developing Alzheimer’s disease (AD). Whether and how subthreshold risk loci translate into relevant disease pathways, is unknown. We investigate here the involvement of AD risk variants in the transcriptional responses of two mouse models: APPswe/PS1L166P and Thy-TAU22. A unique gene expression module, highly enriched for AD risk genes, is specifically responsive to Aβ but not TAU pathology. We identify in this module 7 established AD risk genes (APOE, CLU, INPP5D, CD33, PLCG2, SPI1 and FCER1G) and 11 AD GWAS genes below the genome-wide significance threshold (GPC2, TREML2, SYK, GRN, SLC2A5, SAMSN1, PYDC1, HEXB, RRBP1, LYN and BLNK), that become significantly upregulated when exposed to Aβ. Single microglia sequencing confirms that Aβ, not TAU, pathology induces marked transcriptional changes in microglia, including increased proportions of activated microglia. We conclude that genetic risk of AD functionally translates into different microglia pathway responses to Aβ pathology, placing AD genetic risk downstream of the amyloid pathway but upstream of TAU pathology.
Project description:Polygenic risk scores have identified that genetic variants without genome-wide significance still add to the genetic risk of developing Alzheimer’s disease (AD). Whether and how subthreshold risk loci translate into relevant disease pathways, is unknown. We investigate here the involvement of AD risk variants in the transcriptional responses of two mouse models: APPswe/PS1L166P and Thy-TAU22. A unique gene expression module, highly enriched for AD risk genes, is specifically responsive to Aβ but not TAU pathology. We identify in this module 7 established AD risk genes (APOE, CLU, INPP5D, CD33, PLCG2, SPI1 and FCER1G) and 11 AD GWAS genes below the genome-wide significance threshold (GPC2, TREML2, SYK, GRN, SLC2A5, SAMSN1, PYDC1, HEXB, RRBP1, LYN and BLNK), that become significantly upregulated when exposed to Aβ. Single microglia sequencing confirms that Aβ, not TAU, pathology induces marked transcriptional changes in microglia, including increased proportions of activated microglia. We conclude that genetic risk of AD functionally translates into different microglia pathway responses to Aβ pathology, placing AD genetic risk downstream of the amyloid pathway but upstream of TAU pathology.
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:Alzheimer's disease (AD), the most common form of dementia, is characterized by the abnormal accumulation of amyloid plaques and hyperphosphorylated tau aggregates, as well as microgliosis. The link between mutations in Triggering Receptor Expressed on Myeloid Cells 2 (TREM2), a microglia-expressed gene, and the increased risk for developing late-onset AD suggests a detrimental role for microglia in disease pathophyioslogy. Hemizygous TREM2 mutations are posited to increase risk for AD through loss-of-function haploinsufficiency. The effects of TREM2 haploinsufficiency on tau pathology and tau-associated deficits have not yet been characterized. Using in vivo imaging, we showed that TREM2 haploinsufficiency, but not complete loss of TREM2, resulted in a striking agedependent impairment in microglia’s response to injury without affecting baseline motility. This TREM2-dependent effect on microglial motility is consistent with transcriptomic alterations in cell motility uncovered with unbiased RNAsequencing analysis. Moreover, TREM2 haploinsufficiency, but not complete loss of TREM2, exacerbated phosphorylated tau pathology in transgenic mice expressing mutant human tau. In addition, TREM2 haploinsufficiency increased tau inclusions and tau-mediated inflammation without further exacerbating neuronal loss. Our findings demonstrate for the first time that TREM2 haploinsufficiency induces deficits in a tauopathy mouse model, supporting the notion that the hemizygous missense variant results in loss-of-function.