Project description:The templated misfolding of tau proteins accounts for tau pathology spread in Alzheimer’s disease (AD). Post-translational modifications, including phosphorylation at specific residues, are closely linked with tau seeding ability and clinical disease progression. This study investigates the role of astrocytes in tau spread, demonstrating that tau aggregates from post-mortem AD brain are internalized and processed by human astrocytes. Differences in tau internalization, clearance, and seeding were observed, potentially reflecting the molecular properties of tau. A direct relationship between tau handling by astrocytes and astrocyte responses was noted in transcriptomic data, highlighting dysregulated genes linked to pathological tau clearance pathways. To explore these differences, mass spectrometry was performed on both control and AD brain extracts, providing insights into the complex interplay between tau diversity and astrocyte responses in AD.
Project description:Protein aggregation of amyloid-β (Aβ) peptides and tau are pathological hallmarks of Alzheimer's disease (AD), which are often resistant to detergent extraction and thus enriched in the insoluble proteome. However, additional proteins that co-accumulate in the detergent-insoluble AD brain proteome remain less studied. Here we comprehensively characterized key proteins and pathways in the detergent-insoluble proteome from human AD brain samples by differential extraction, coupled with tandem mass tags labeling and two-dimensional liquid chromatography tandem mass spectrometry (TMT-LC/LC-MS/MS).
Project description:Genetic studies implicate Clusterin (CLU) in the pathogenesis of Alzheimer’s disease (AD), yet its precise molecular impact remains unclear. Through unbiased proteomic profiling and functional validation in CLU-deficient astrocytes, we identify increased NfkB-dependent signaling and complement C3 secretion. Reduction of astrocyte CLU induced microglia dependent modulation of extracellular APOE and phosphorylated tau, as well as increased microglial phagocytosis and reduced synapse numbers. By integrating mouse and human cellular models with comprehensive analyses of human plasma and brain tissue, we demonstrate that CLU AD risk alleles are associated with reduced CLU protein and heightened inflammatory profiles. These findings establish a mechanistic link between AD genetic risk factors, astrocyte reactivity, and microglia-mediated effects on synaptic integrity. Collectively, these results support a model in which CLU upregulation in response to neuropathology is associated with maintenance of cognitive function, while diminished astrocyte CLU levels heighten disease susceptibility.
Project description:Genetic studies implicate Clusterin (CLU) in the pathogenesis of Alzheimer’s disease (AD), yet its precise molecular impact remains unclear. Through unbiased proteomic profiling and functional validation in CLU-deficient astrocytes, we identify increased NfkB-dependent signaling and complement C3 secretion. Reduction of astrocyte CLU induced microglia dependent modulation of extracellular APOE and phosphorylated tau, as well as increased microglial phagocytosis and reduced synapse numbers. By integrating mouse and human cellular models with comprehensive analyses of human plasma and brain tissue, we demonstrate that CLU AD risk alleles are associated with reduced CLU protein and heightened inflammatory profiles. These findings establish a mechanistic link between AD genetic risk factors, astrocyte reactivity, and microglia-mediated effects on synaptic integrity. Collectively, these results support a model in which CLU upregulation in response to neuropathology is associated with maintenance of cognitive function, while diminished astrocyte CLU levels heighten disease susceptibility.
Project description:Protein aggregation of amyloid beta peptides and tau are pathological hallmarks of Alzheimer's disease (AD), which are often resistant to detergent extraction and thus enriched in the insoluble proteome. However, additional proteins that co-accumulate in the detergent-insoluble AD brain proteome remain less studied. Here we comprehensively characterized key proteins and pathways in the detergent-insoluble proteome from human AD brain samples by differential extraction, coupled with tandem mass tags labeling and two-dimensional liquid chromatography tandem mass spectrometry (TMT-LC/LC-MS/MS).
Project description:Core spliceosome and related RNA-binding proteins aggregate in Alzheimer’s disease (AD) brain even in early asymptomatic stages (AsymAD) of disease. To assess the specificity of RNA-binding protein aggregation in AD, we developed a targeted mass spectrometry approach to quantify broad classes of RNA-binding proteins with other pathological proteins including Tau and amyloid beta (Aβ) in detergent insoluble fractions from AD brain and that of other dementias. In total, we quantified 870 peptides from 385 detergent-insoluble RNA-binding proteins across 44 cortical tissues including controls, AsymAD, AD, and Parkinson’s Disease (PD). Relative levels of specific insoluble RNA-binding proteins across different disease groups correlated with accumulation of Aβ and Tau aggregates. RNA-binding proteins, including splicing factors with homology to the basic-acidic dipeptide repeats of U1-70K, preferentially aggregated in AsymAD and AD. In contrast, PD brain aggregates were relatively depleted of many RNA-binding proteins compared to AsymAD and AD groups. Correlation network analyses resolved 29 distinct modules of co-aggregating proteins including modules linked to spliceosome assembly, nuclear speckles and RNA splicing. Modules related to spliceosome assembly and nuclear speckles progressively increased in insolubility across progressive AD stages, whereas the RNA splicing module was decreased specifically in PD. Collectively, this work identifies classes of RNA-binding proteins that distinctly co-aggregate in detergent-insoluble fractions across neurodegenerative diseases.
Project description:Proteomic sequencing of postmortem human brain can identify dysfunctional proteins that contribute to neurodegenerative disorders like Alzheimer’s disease and frontotemporal dementia. Similar studies in chronic traumatic encephalopathy are limited, but may provide important new insights into this disorder. Given our previous success with identifying pathology associated proteins, we performed proteomic sequencing of detergent insoluble brain homogenates from frontal cortex of deceased subjects with CTE covering a range of CTE pathologic stages. We compared the insoluble proteome of CTE brain to control and AD brains to identify differentially expressed proteins. We identified over 4000 proteins in CTE brains, including significant enrichment of the microtubule associated protein tau. We also found enrichment and pathologic aggregation of RNA processing factors as seen previously in AD, supporting the previously recognized overlap between AD and CTE. In addition to these similarities, we identified CTE-specific enrichment of a number of proteins which increase with increasing severity of CTE pathology. NADPH dehydrogenase quinone 1 (NQO1) was one of the proteins which showed significant enrichment in CTE and also correlated with increasing CTE stage. NQO1 demonstrated neuropathologic correlation with hyperphosphorylated tau in glial cells, mainly astrocytes. These results demonstrate that quantitative proteomic sequencing of CTE postmortem human brain can identify disease relevant findings and novel cellular pathways involved in CTE pathogenesis.
Project description:Communication within the glial cell ecosystem is essential for neuronal and brain health1–3. The influence of glial cells on the accumulation and clearance of β-amyloid (Aβ) and neurofibrillary tau in the brains of individuals with Alzheimer’s disease (AD) is poorly understood, despite growing awareness that these are therapeutically important interactions4,5. Here we show, in humans and mice, that astrocyte-sourced interleukin-3 (IL-3) programs microglia to ameliorate the pathology of AD. Upon recognition of Aβ deposits, microglia increase their expression of IL-3Rα—the specific receptor for IL-3 (also known as CD123)—making them responsive to IL-3. Astrocytes constitutively produce IL-3, which elicits transcriptional, morphological, and functional programming of microglia to endow them with an acute immune response program, enhanced motility, and the capacity to cluster and clear aggregates of Aβ and tau. These changes restrict AD pathology and cognitive decline. Our findings identify IL-3 as a key mediator of astrocyte–microglia cross-talk and a node for therapeutic intervention in AD.
Project description:Microglia are critical for brain development and play a central role in Alzheimer’s disease (AD) etiology. Down syndrome (DS), also known as trisomy 21, is the most common genetic origin of intellectual disability and the most common risk factor for AD. Surprisingly, little information is available on the impact of trisomy of human chromosome 21 (Hsa21) on microglia in DS brain development and AD in DS (DSAD). Using our new induced pluripotent stem cell (iPSC)-based human microglia-containing cerebral organoid and chimeric mouse brain models, here we report that DS microglia exhibit enhanced synaptic pruning function during brain development. Consequently, electrophysiological recordings demonstrate that DS microglial mouse chimeras show impaired synaptic neurotransmission, as compared to control microglial chimeras. Upon being exposed to human brain tissue-derived soluble pathological tau, DS microglia display dystrophic phenotypes in chimeric mouse brains, recapitulating microglial responses seen in human AD and DSAD brain tissues. Further flow cytometry, single-cell RNA-sequencing, and immunohistological analyses of chimeric mouse brains demonstrate that DS microglia undergo cellular senescence and exhibit elevated type I interferon signaling after being challenged by pathological tau. Mechanistically, we find that shRNA-mediated knockdown of Hsa21-encoded type I interferon receptor genes, IFNARs, rescues the defective DS microglial phenotypes both during brain development and in response to pathological tau. Our findings provide in vivo evidence supporting a paradigm shifting theory that human microglia respond to pathological tau with accelerated senescence. Our results further suggest that targeting IFNARs may improve microglial functions during DS brain development and prevent human microglial senescence in DS individuals with AD.
Project description:Microglia are critical for brain development and play a central role in Alzheimer’s disease (AD) etiology. Down syndrome (DS), also known as trisomy 21, is the most common genetic origin of intellectual disability and the most common risk factor for AD. Surprisingly, little information is available on the impact of trisomy of human chromosome 21 (Hsa21) on microglia in DS brain development and AD in DS (DSAD). Using our new induced pluripotent stem cell (iPSC)-based human microglia-containing cerebral organoid and chimeric mouse brain models, here we report that DS microglia exhibit enhanced synaptic pruning function during brain development. Consequently, electrophysiological recordings demonstrate that DS microglial mouse chimeras show impaired synaptic neurotransmission, as compared to control microglial chimeras. Upon being exposed to human brain tissue-derived soluble pathological tau, DS microglia display dystrophic phenotypes in chimeric mouse brains, recapitulating microglial responses seen in human AD and DSAD brain tissues. Further flow cytometry, single-cell RNA-sequencing, and immunohistological analyses of chimeric mouse brains demonstrate that DS microglia undergo cellular senescence and exhibit elevated type I interferon signaling after being challenged by pathological tau. Mechanistically, we find that shRNA-mediated knockdown of Hsa21-encoded type I interferon receptor genes, IFNARs, rescues the defective DS microglial phenotypes both during brain development and in response to pathological tau. Our findings provide in vivo evidence supporting a paradigm shifting theory that human microglia respond to pathological tau with accelerated senescence. Our results further suggest that targeting IFNARs may improve microglial functions during DS brain development and prevent human microglial senescence in DS individuals with AD.