Single-cell resolution spatial transcriptomics enables transcriptome-wide molecular profiling within intact tissue architecture, providing unprecedented opportunities to investigate cellular organization and disease-associated molecular states in the human brain. However, applying these technologies to post-mortem human brain tissue remains challenging due to RNA degradation, heterogeneity in tissue preservation, and a lack of standardized analytical workflows. These challenges are particularly pronounced for whole-transcriptome platforms, where successful implementation requires optimization of both experimental and computational procedures. Here, we present an end-to-end framework for single-cell-resolution, whole-transcriptome spatial transcriptomics of fresh-frozen (FF) and formalin-fixed paraffin-embedded (FFPE) post-mortem human brain tissue. The framework combines an optimized experimental workflow with a preservation-agnostic bioinformatics pipeline for data processing, integration, and annotation. Experimentally, we show that a condensed two-day Visium HD workflow provides improved library quality, lowered qPCR cycle thresholds, and more consistent fragment size distributions. Sequencing saturation analyses further identified cost-effective sequencing depths that maximize transcript recovery while minimizing redundant sequencing. Computationally, we established a scalable workflow incorporating DAPI-based nuclear segmentation, transcript assignment, quality control, reference-guided integration, clustering, and cell-type annotation. We implemented a reference-based highly variable gene selection strategy to enable robust cross-sample harmonization independent of tissue preservation method. Application of this framework to seven Alzheimer's disease frontal cortex specimens (five FF and two FFPE) generated a unified single-cell spatial transcriptomic atlas comprising more than 530,000 spatially resolved cells. The integrated dataset resolved major neuronal, glial, and vascular cell populations, recapitulated expected cortical architecture, and enabled direct comparison of FF- and FFPE-derived spatial transcriptomic profiles. Together, this work provides a practical experimental and computational framework for single-cell resolution, whole-transcriptome spatial transcriptomics in post-mortem human brain tissue and delivers a publicly available resource that expands the utility of archived and frozen specimens for studies of neurodegeneration and other neurological disorders. Importance:Spatial transcriptomics of human post-mortem brain tissue is limited by RNA degradation, preservation variability, and lack of standardized workflows. Here, we present an end-to-end framework combining an optimized two-day Visium HD protocol with a preservation-agnostic bioinformatics pipeline. This approach improves library quality, defines efficient sequencing strategies, and enables robust spatial profiling across both FF and FFPE samples. Applied to Alzheimer's disease brain tissue, it generates high-resolution single-cell spatial data and expands the utility of archived and frozen specimens for studying neurodegenerative diseases.

BCL2-associated anthanogene 3 facilitates the clearance of tau protein aggregates:BCL2-associated anthanogene 3(BAG3)is a ubiquitously expressed and highly conserved multi-functional co-chaperone protein involved in many biological processes that supports cellular homeostasis,including the inhibition of apoptosis by preventing mitochondrial BAX localization(Lin et al.,2022)and the promotion of the degradation of hyperphosphorylated tau aggregates by its interactions with SQSTM1(p62)(Hamano and Mutoh,2022).

Higher ectodermal-neural cortex 1 (ENC1) RNA level is correlated with higher residual cognition in participants of the Religious Orders Study and the Rush Memory and Aging Project. Transcriptomic analyses show decreased overall ENC1 mRNA in human brains with Alzheimer's disease (AD) compared to control brains. We have previously identified ENC1 as one of the hub genes controlling tau homeostasis via the weighted gene co-expression network analysis of healthy donors. However, the relationship between ENC1 and tau remains unclear. We hypothesize that ENC1 interacts with tau and enhances tau clearance via the autophagy-lysosome pathway (ALP), inhibiting tau propagation . The co-immunoprecipitation and Duolink assay were used to measure the interaction between human ENC1 and tau in vitro and in human brains. The specific knockdown of ENC1 (mainly in the nucleus) in excitatory neurons (ENs) at the superficial layers of adult mouse entorhinal cortex (EC) was achieved by stereotaxic injection of AAV8-CaMKIIa-Cre in the EC of ENC1 flox/flox mice. An autophagy reporter mouse (TRGL6) (mRFP-eGFP-LC3) and TRGL6;PS19 tau mice were used to measure the effect of ENC1 on autophagy dynamics. The tau propagation was measured by stereotaxic injection of a tau-propagation reporter virus (AAV8-hSyn-RFP-2A-V5-Tau) or TBS-soluble human tau seeds in the EC of ENC1 flox/flox mice. We found that ENC1 interacted with both total tau protein (TauC+) and pathological tau (TauY9+), and this interaction was significantly increased in human AD brains compared to controls. Conditional knockdown of ENC1 in ENs of TRGL6;ENC1 flox/flox and TRGL6;PS19;ENC1 flox/flox mice significantly reduced the number of single red puncta (autolysosomes) and increased the yellow puncta (autophagosome and poorly acidified autolysosomes), suggesting the ALP was impaired. Also, the knockdown of ENC1 specifically in ENs of the EC significantly increased the number of V5 only positive tau recipient neurons or MC1-positive (conformation-dependent tau) in the spreading areas such as deep layers of the EC and the hippocampal CA1. These results suggest that conditional knockdown of ENC1 in ENs could promote tau propagation in vivo . We demonstrate that ENC1 is a novel modulator of tau protein homeostasis by regulating tau clearance and propagation probably via the regulation of ALP.

Recent Genome-Wide Association Studies (GWAS) have identified novel rare coding variants (P522R, M28L variants) of the enzyme phospholipase-C-γ2 (PLCG2) in late-onset Alzheimer's Disease (LOAD). PLCG2 is a well-known transmembrane-associated enzyme, functioning downstream of immune receptors such as TREM2 in LOAD. It is reported that the PLCG2 P522R variant plays a protective role in AD and longevity by enhancing Aβ clearance and modulating microglial function. The role of PLCG2 and its variants in AD has been largely investigated in microglia and responses to Aβ pathology; however, little is known about the role of PLCG2 and its AD variants in other cell types or its role in tau pathology. PLCG2 is also a well-known second messenger that activates the phosphorylation of GSK3β, which may lead to decreased tau hyperphosphorylation and promotion of the autophagy-lysosomal pathway (ALP). Thus, we hypothesize that deficiency of excitatory neuronal PLCG2 enhances tau aggregation and propagation in AD by inhibiting the ALP . To evaluate the immunoreactivity of PLCG2 and its relationship with tau pathology, we performed western blot and immunofluorescence staining on human post-mortem brains and PS19 tau mice. By stereotaxic injection of AAV8-CaMKIIa-cre and AD TBS-soluble tau seeds in PLCG2-floxed mice, we quantified tau spreading induced by PLCG2 knockdown. To further identify the role of the PLCG2 P522R variant (gain-of-function) in a complex human brain-like environment, we generated human neural organoids derived from human iPSCs of a healthy donor and a CRISPR/Cas9-edited PLCG2 P522R knock-in (KI) cell line. To investigate ALP dynamics induced by PLCG2, we used FUW-mCherry-GFP-LC3 reporter assay in P522R KI organoids. We found higher global protein levels of PLCG2 in human AD cases and PS19 mice, but pathological tau-positive cells had a lower level of PLCG2 than neighboring pathological tau-negative cells. Knockdown of PLCG2 in excitatory neurons increased tau spreading in PLCG2-floxed mice. Autophagy flux increased in P522R KI organoids, even in the presence of Bafilomyacin-A1 (autophagy inhibitor), compared to wild-type organoids. These results suggest that repression or dysfunction of PLCG2 may contribute to tau pathology in excitatory neurons of AD, probably via the regulation of the ALP.

>Alzheimer's disease(AD) is the most common form of dementia. In addition to the lack of effective treatments, there are limitations in diagnostic capabilities. The complexity of AD itself, together with a variety of other diseases often observed in a patient's history in addition to their AD diagnosis, make deciphering the molecular mechanisms that underlie AD, even more important.

Lipid dyshomeostasis and tau pathology are present in frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD). However, the relationship between lipid dyshomeostasis and tau pathology remains unclear. We report that GRAM Domain Containing 1B (GRAMD1B), a nonvesicular cholesterol transporter, is increased in excitatory neurons of human neural organoids (HNOs) with the MAPT R406W mutation. Human FTLD, AD cases, and PS19 tau mice also have increased GRAMD1B expression. We show that overexpression of GRAMD1B increases levels of free cholesterol, lipid droplets, and impairs autophagy flux. Modulating GRAMD1B in iPSC-derived neurons also alters key autophagy-related components such as PI3K, phospho-AKT, and p62, as well as phosphorylated tau, and CDK5R1. Blocking GRAMD1B function decreases free cholesterol and lipid droplets. Knocking down GRAMD1B additionally reduces phosphorylated tau, and CDK5R1 expression. Our findings elucidate the role of GRAMD1B in the nervous system and highlight its relevance to FTLD and AD.

Aggregation of microtubule-associated tau protein is a distinct hallmark of several neurodegenerative disorders such as Alzheimer’s disease (AD), dementia with Lewy bodies (DLB), and progressive supranuclear palsy (PSP). Tau oligomers are suggested to be the primary neurotoxic species that initiate aggregation and propagate prion-like structures. Furthermore, different diseases are shown to have distinct structural characteristics of aggregated tau, denoted as polymorphs. Here, we investigate the structural and functional differences of amplified brain-derived tau oligomers (aBDTOs) from AD, DLB, and PSP. Our results indicate that the aBDTOs possess different structural and morphological features that impact neuronal function, gene regulation, and ultimately disease progression. The distinct tau oligomeric polymorphs may thus contribute to the development of clinical phenotypes and shape the progression of diseases. Our results can provide insight into developing personalized therapy to target a specific neurotoxic tau polymorph. Different aggregation characteristics and stability profiles of tau oligomeric polymorphs highlight the importance of studying the tau polymorphs to shed light on the functional differences and neuropathological heterogeneity in tauopathies.

Background Substantial evidence has established the critical role of microglia, the brain's resident immune cells, in the pathogenesis of Alzheimer's disease (AD). Microglia exhibit diverse transcriptional states in response to neuroinflammatory stimuli, and understanding these states is crucial for elucidating the underlying mechanisms of AD. Methods In this work, we integrated single-cell and spatially resolved transcriptomics data from multiple cohorts and brain regions, including microglia from experimental and human brains. Results This comprehensive atlas revealed a great heterogeneity of microglial states, with a significant enrichment of specific states, including activated microglia, in AD brains compared to controls. Further integration of spatial transcriptomics and immunohistochemistry showed that activated microglia are predominantly located in the external cortical layers near amyloid plaques, while homeostatic microglia are more prevalent in the internal cortical layers and further away from the plaques. These spatial patterns were further validated using P2RY12 immunostaining, which confirmed the reliability of the transcriptomic data. Conclusion By integrating single-cell and spatial transcriptomics, we have provided a detailed atlas of microglial diversity, revealing the regional and pathological specificity of microglial states.

Cellular cross-talk, mediated by membrane receptors and their ligands, is crucial for brain homeostasis and can contribute to neurodegenerative diseases such as Alzheimer’s disease (AD). To find cross-talk dysregulations involved in AD, we reconstructed cross-talk networks from single-nucleus transcriptional profiles of 67 clinically and neuropathologically well-characterized controls and AD brain donors from the Knight Alzheimer Disease Research Center and the Dominantly Inherited Alzheimer Network cohorts. We predicted a role for TREM2 and additional AD risk genes mediating neuron-microglia cross-talk in AD. We identified a gene network mediating neuron-microglia cross-talk through TREM2 and neuronal SEMA6D, which we predicted is disrupted in late AD stages. Using spatial transcriptomics on the human brain, we observed that the SEMA6D-TREM2 cross-talk gene network is activated near Aβ plaques and SEMA6D-expressing cells. Using tissue immunostaining of human brains, we found that SEMA6D colocalizes with Aβ plaques and TREM2-activated microglia. In addition, we found that plaque-proximal SEMA6D abundance decreased with the disease stage, which correlated with a reduction in microglial activation near plaques. These findings suggest that the loss of SEMA6D signaling impairs microglial activation and Αβ clearance. To validate this hypothesis, we leveraged TREM2 knockout human induced pluripotent stem cell–derived microglia and observed that SEMA6D induces microglial activation and Aβ plaque phagocytosis in a TREM2-dependent manner. In summary, we demonstrate that characterizing cellular cross-talk networks can yield insights into AD biology, provide additional context to understand AD genetic risk, and find previously unknown therapeutic targets and pathways.

BackgroundPathogenic tau accumulation drives neurodegeneration in Alzheimer's disease (AD). Enhancing the aging brain's resilience to tau pathology would lead to novel therapeutic strategies. DAP12 (DNAX-activation protein 12), highly and selectively expressed by microglia, plays a crucial role in microglial immune responses. Previous studies have shown that tauopathy mice lacking DAP12 exhibit higher tau pathology but are protected from tau pathology-induced cognitive deficits. However, the exact mechanism behind this resilience remains elusive.MethodsWe investigated the effects of DAP12 deletion on tau pathology, as well as tau-induced brain inflammation and neurodegeneration, in homozygous human Tau P301S transgenic mice. In addition, we conducted single-nucleus RNA sequencing of hippocampal tissues to examine cell type-specific transcriptomic changes at the single-cell level. Furthermore, we utilized the CellChat package to profile cell-cell communication in the mouse brain and investigated how these interactions are affected by tau pathology and Dap12 deletion.ResultsWe demonstrated that Dap12 deletion reduced tau processing in primary microglia and increased tau pathology in female tauopathy mice, with minimal effects on males. Despite this, Dap12 deletion markedly reduced brain inflammation, synapse loss, and demyelination, indicating enhanced resilience to tau toxicity. Single-cell transcriptomic profiling revealed that Dap12 deletion blocked tau-induced alterations in microglia, neurons, and oligodendrocytes. CellChat analysis identified aberrant tau-induced SLIT2 signaling from excitatory neurons to oligodendrocytes. Dap12 deletion suppressed Slit2 upregulation and mitigated demyelination, while lentiviral-Slit2 overexpression induced myelin loss in tauopathy mice. Elevated SLIT2 levels were associated with demyelination in tauopathy mouse model and human AD brains. Spatial transcriptomics revealed a spatial correlation of SLIT2 expression and tau pathology in AD brain tissue.ConclusionsOur study identifies a novel DAP12-dependent mechanistic link between upregulated Slit2 expression in excitatory neurons and oligodendrocyte-dependent myelination loss in tauopathy. Despite elevating tau load, the absence of microglial Dap12 ameliorates neuroinflammation and improves brain functions in tauopathy mice. Our study suggests that selectively targeting the toxic aspects of DAP12 signaling while preserving its beneficial functions may be a promising strategy to enhance brain resilience in AD.

Alzheimer's Disease (AD) pathology has been increasingly explored through single-cell and single-nucleus RNA-sequencing (scRNA-seq & snRNA-seq) and spatial transcriptomics (ST). However, the surge in data demands a comprehensive, user-friendly repository. Addressing this, we introduce a single-cell and spatial RNA-seq database for Alzheimer's disease (ssREAD). It offers a broader spectrum of AD-related datasets, an optimized analytical pipeline, and improved usability. The database encompasses 1,053 samples (277 integrated datasets) from 67 AD-related scRNA-seq & snRNA-seq studies, totaling 7,332,202 cells. Additionally, it archives 381 ST datasets from 18 human and mouse brain studies. Each dataset is annotated with details such as species, gender, brain region, disease/control status, age, and AD Braak stages. ssREAD also provides an analysis suite for cell clustering, identification of differentially expressed and spatially variable genes, cell-type-specific marker genes and regulons, and spot deconvolution for integrative analysis. ssREAD is freely available at https://bmblx.bmi.osumc.edu/ssread/.

Growing evidence supports that early- or middle-life traumatic brain injury (TBI) is a risk factor for developing Alzheimer’s disease (AD) and AD-related dementia (ADRD). Nevertheless, the molecular mechanisms underlying TBI-induced AD-like pathology and cognitive deficits remain unclear. In this study, we found that a single TBI (induced by controlled cortical impact) reduced the expression of BCL2-associated athanogene 3 (BAG3) in neurons and oligodendrocytes, which is associated with decreased proteins related to the autophagy-lysosome pathway (ALP) and increased hyperphosphorylated tau (ptau) accumulation in excitatory neurons and oligodendrocytes, gliosis, synaptic dysfunction, and cognitive deficits in wild-type (WT) and human tau knock-in (hTKI) mice. These pathological changes were also found in human cases with a TBI history and exaggerated in human AD cases with TBI. The knockdown of BAG3 significantly inhibited autophagic flux, while overexpression of BAG3 significantly increased it in vitro. Specific overexpression of neuronal BAG3 in the hippocampus attenuated AD-like pathology and cognitive deficits induced by TBI in hTKI mice, which is associated with increased ALP-related proteins. Our data suggest that targeting neuronal BAG3 may be a therapeutic strategy for preventing or reducing AD-like pathology and cognitive deficits induced by TBI.

Alzheimer’s Disease (AD) is a neurodegenerative disease characterized by profound memory impairments, synaptic loss, neuroinflammation, and hallmark pathological markers. High-fat diet (HFD) consumption increases the risk of developing AD even after controlling for metabolic syndrome, pointing to a role of the diet itself in increasing risk. In AD, the complement system, an arm of the immune system which normally tags redundant or damaged synapses for pruning, becomes pathologically overactivated leading to tagging of healthy synapses. While the unhealthy diet to AD link is strong, the underlying mechanisms are not well understood in part due to confounding variables associated with long-term HFD which can independently influence the brain. Therefore, we experimented with a short-term diet regimen to isolate the diet’s impact on brain function without causing obesity. This project investigated the effect of short-term HFD on 1) memory, 2) neuroinflammation including complement, 3) AD pathology markers, 4) synaptic markers, and 5) in vitro microglial synaptic phagocytosis in the 3xTg-AD mouse model. Following the consumption of either standard chow or HFD, 3xTg-AD and non-Tg mice were tested for memory impairments. In a separate cohort of mice, levels of hippocampal inflammatory markers, complement proteins, AD pathology markers, and synaptic markers were measured. For the last set of experiments, BV2 microglial phagocytosis of synapses was evaluated. Synaptoneurosomes isolated from the hippocampus of 3xTg-AD mice fed chow or HFD were incubated with equal numbers of BV2 microglia. The number of BV2 microglia that phagocytosed synaptoneurosomes was tracked over time with a live-cell imaging assay. Finally, we incubated BV2 microglia with a complement receptor inhibitor (NIF) and repeated the assay. Behavioral analysis showed 3xTg-AD mice had significantly impaired long-term contextual and cued fear memory compared to non-Tg mice that was further impaired by HFD. HFD significantly increased inflammatory markers and complement expression while decreasing synaptic marker expression only in 3xTg-AD mice without altering AD pathology markers. Synaptoneurosomes from HFD-fed 3xTg-AD mice were phagocytosed at a significantly higher rate than those from chow-fed mice, suggesting the synapses were altered by HFD. The complement receptor inhibitor blocked this effect in a dose-dependent manner, demonstrating the HFD-mediated increase in phagocytosis was complement dependent. This study indicates HFD consumption increases neuroinflammation and over-activates the complement cascade in 3xTg-AD mice, resulting in poorer memory. The in vitro data point to complement as a potential mechanistic culprit and therapeutic target underlying HFD’s influence in increasing cognitive vulnerability to AD.

Deciphering the intricate relationships between transcription factors (TFs), enhancers, and genes through the inference of enhancer-driven gene regulatory networks (eGRNs) is crucial in understanding gene regulatory programs in a complex biological system. This study introduces STREAM, a novel method that leverages a Steiner forest problem model, a hybrid biclustering pipeline, and submodular optimization to infer eGRNs from jointly profiled single-cell transcriptome and chromatin accessibility data. Compared to existing methods, STREAM demonstrates enhanced performance in terms of TF recovery, TF-enhancer linkage prediction, and enhancer-gene relation discovery. Application of STREAM to an Alzheimer's disease dataset and a diffuse small lymphocytic lymphoma dataset reveals its ability to identify TF-enhancer-gene relations associated with pseudotime, as well as key TF-enhancer-gene relations and TF cooperation underlying tumor cells.

Tau aggregate-bearing lesions are pathological markers and potential mediators of tauopathic neurodegenerative diseases, including Alzheimer's disease. The molecular chaperone DJ-1 colocalizes with tau pathology in these disorders, but it has been unclear what functional link exists between them. In this study, we examined the consequences of tau/DJ-1 interaction as isolated proteins in vitro. When added to full-length 2N4R tau under aggregation-promoting conditions, DJ-1 inhibited both the rate and extent of filament formation in a concentration-dependent manner. Inhibitory activity was low affinity, did not require ATP, and was not affected by substituting oxidation incompetent missense mutation C106A for wild-type DJ-1. In contrast, missense mutations previously linked to familial Parkinson's disease and loss of α-synuclein chaperone activity, M26I and E64D, displayed diminished tau chaperone activity relative to wild-type DJ-1. Although DJ-1 directly bound the isolated microtubule-binding repeat region of tau protein, exposure of preformed tau seeds to DJ-1 did not diminish seeding activity in a biosensor cell model. These data reveal DJ-1 to be a holdase chaperone capable of engaging tau as a client in addition to α-synuclein. Our findings support a role for DJ-1 as part of an endogenous defense against the aggregation of these intrinsically disordered proteins.

Pathogenic tau accumulation fuels neurodegeneration in Alzheimer's disease (AD). Enhancing aging brain's resilience to tau pathology would lead to novel therapeutic strategies. DAP12 (DNAX-activation protein 12) is critically involved in microglial immune responses. Previous studies have showed that mice lacking DAP12 in tauopathy mice exhibit higher tau pathology but are protected from tau-induced cognitive deficits. However, the exact mechanism remains elusive. Our current study uncovers a novel resilience mechanism via microglial interaction with oligodendrocytes. Despite higher tau inclusions, Dap12 deletion curbs tau-induced brain inflammation and ameliorates myelin and synapse loss. Specifically, removal of Dap12 abolished tau-induced disease-associated clusters in microglia (MG) and intermediate oligodendrocytes (iOli), which are spatially correlated with tau pathology in AD brains. Our study highlights the critical role of interactions between microglia and oligodendrocytes in tau toxicity and DAP12 signaling as a promising target for enhancing resilience in AD.

Selective vulnerability of excitatory neurons in Alzheimer’s disease (AD): AD is the most common form of dementia; however, the pathogenesis of AD is largely unknown. One of the characteristic features of AD is the formation of intracellular neurofibrillary tangles (NFTs). NFTs are abnormal accumulates of misfolded tau protein, which may eventually cause neuronal death and neurodegeneration (Jack et al., 2018). In the early stages of AD progression, not all neurons are equally vulnerable to tau aggregates. Previous studies have shown that large pyramidal neurons in the entorhinal cortex (EC) are specifically vulnerable to pathological tau accumulation (Fu et al., 2017). This selective vulnerability of excitatory neurons to tau pathology is one of the fundamental questions needed to be answered in AD research. Techniques such as single-nucleus RNA sequencing enable us to

Alzheimer disease (AD) and traumatic brain injury (TBI) are two devastating brain disorders with complex relationships. Growing evidence supports that early or middle life of TBI may be a risk factor for developing late-life AD and AD-related dementias (ADRD). Tau hyperphosphorylation and gliosis may serve as a causative link between TBI and AD as well as ADRD. We have recently identified BCL2 associated athanogene 3 (BAG3) as a hub gene of regulating tau protein homeostasis. The protein level of BAG3 is significantly reduced in neurons, but it is increased in astrocytes of human AD compared to controls. We hypothesized that overexpression of BAG3 in neurons would attenuate tau hyperphosphorylation and gliosis induced by TBI. We injected 500 nL AAV9-hSYN1-eGFP-2A-hBAG3-WPRE or AAV9-hSYN1-eGFP-WPRE (control AAV9) into the hippocampal CA1 and DG regions of C57BL6/J and htau knock-in mice. These mice were subjected to TBI surgery (controlled cortical impact, velocity: 3.00 m/s, depth: 0.8 mm, dwell time: 200 ms) three months post the injection. We then performed behavioral tests (open-field test, Y-maze, and Morris Water Maze) on these mice one month after the CCI surgery. Following the behavioral tests, we collected the brain tissues and performed the immunofluorescent staining of ptau (PHF1, pS396/404 tau), BAG3, IBA-1 (microglia/macrophage marker) and GFAP (astrocyte marker) on fixed mouse brain floating sections. TBI increased the immunoreactivity of PHF1, IBA-1, GFAP and astrocytic BAG3, whereas reducing neuronal BAG3 compared to sham C57BL6/J and htau knock-in mice. Furthermore, the immunoreactivity of BAG3 increased, while PHF1, IBA-1 and GFAP decreased in the ipsilateral hippocampus after the injection of AAV9-BAG3 compared to those TBI mice injected with control AAVs. Continued immunofluorescent staining and quantification for AAV9-BAG3- and control AAV9-injected mice is currently ongoing, as is behavior data quantification. TBI induces tau hyperphosphorylation, microglia activation and reactive astrocytes, while reducing neuronal BAG3 in C57BL6/J and htau knock-in mice. Neuronal overexpression of BAG3 can significantly attenuate tau hyperphosphorylation and gliosis induced by TBI. Our data suggests that targeting neuronal BAG3 may be a therapeutic strategy for preventing or reducing intra-neuronal tau aggregates and gliosis found in TBI and TBI-associated AD and ADRD.

Alzheimer's disease (AD) is a complex neurodegenerative disease, perturbing neuronal and non-neuronal cell populations. In this study, using single-cell transcriptomics, we mapped all non-immune, non-neuronal cell populations in wild-type and AD model (5xFAD) mouse brains. We identified an oligodendrocyte state that increased in association with brain pathology, which we termed disease-associated oligodendrocytes (DOLs). In a murine model of amyloidosis, DOLs appear long after plaque accumulation, and amyloid-beta (Aβ) alone was not sufficient to induce the DOL signature in vitro. DOLs could be identified in a mouse model of tauopathy and in other murine neurodegenerative and autoimmune inflammatory conditions, suggesting a common response to severe pathological conditions. Using quantitative spatial analysis of mouse and postmortem human brain tissues, we found that oligodendrocytes expressing a key DOL marker (SERPINA3N/SERPINA3 accordingly) are present in the cortex in areas of brain damage and are enriched near Aβ plaques. In postmortem human brain tissue, the expression level of this marker correlated with cognitive decline. Altogether, this study uncovers a shared signature of oligodendrocytes in central nervous system pathologies.