Acta Neuropathologica最新文献

Increased expression of syntaxin-6, a SNARE protein involved in intracellular protein trafficking, is a proposed genetic risk mechanism for sporadic prion disease and progressive supranuclear palsy, as well as being implicated in Alzheimer’s disease. However, no study has validated its functional role in prion disease, its mechanism of action nor explored the disease stage at which it is acting. Here, we show that syntaxin-6 knockdown in cellular models increases cell-associated infectivity, whilst overexpression produces the opposite effect. This observation is broadly consistent across multiple cell types and prion strains. Furthermore, syntaxin-6 knockdown leads to an accumulation of perinuclear disease-related PrP, consistent with a trafficking mechanism, and alters the morphology of disease-related PrP. We demonstrate that syntaxin-6 knockdown reduces the secretion of prions from infected cells, which provides a mechanism for the prion-related cellular phenotypes observed. Complementary in vivo studies showed that syntaxin-6 influences early stages of prion disease in experimental mice, increasing transmission risk after inoculation with low prion doses. Conversely, syntaxin-6 does not affect prion propagation kinetics or toxicity during established disease. Taken together, our studies firmly establish syntaxin-6 as a modifier of prion pathogenesis with a role in prion trafficking and export. Our findings further suggest that syntaxin-6 modifies the risk of the establishment of disease in line with its genetic association in humans. Thus, this work provides important insights into the role of a pleiotropic prion/prion-like modifier, grounded in human genetics evidence, which may have wider relevance to other neurodegenerative diseases.

Chronic active lesions are a manifestation of multiple sclerosis (MS) and have been associated with disease progression. While astrocytes are heavily implicated in MS, little is known about their role in lesions, particularly in the lesion core. Here, we sought to gain insight into the spatial relationship between astrocytes and defined regions of chronic active lesions, and to better understand the environment within the relatively understudied lesion core, an area primarily composed of astrocytes. We analyzed four defined protein panels, focusing on astrocytes, in postmortem fresh-frozen cortical white matter tissue using NanoString GeoMx spatial protein profiling to compare normal appearing white matter (NAWM), the chronic active perilesion, rim, and core. We then performed immunofluorescent microscopy to determine the localization patterns of identified proteins within astrocytes. The most significant differences were observed between the chronic active lesion core and both NAWM and the perilesion. Proteins upregulated in the core relative to NAWM or the perilesion included the MAPK signaling pathway, immune checkpoint proteins, and indicators of phagocytosis. Our data indicate that astrocytes in the lesion core are distinct and actively influence the microenvironment. We posit that the differentially upregulated astrocytic signaling pathways, namely MAPK, immune checkpoints, and debris engulfment, are indicative of reactive astrocytes providing support to demyelinated axons by tempering the inflammatory milieu and clearing debris within the lesion core.

Alpha-synuclein (α-syn) deposits are common in around half of the Alzheimer’s disease (AD) cases. While direct and indirect protein interactions are suggested, the relationships between different protein aggregates remain poorly understood. Here, we aimed to characterize α-syn, amyloid beta (Aβ), and tau load distributions of AD patients. Protein deposits were automatically quantified with random forest pixel classifiers in immunohistochemical stains of up to 28 brain regions in 72 brains with advanced AD neuropathological change. α-syn-negative cases were distinguished from amygdala predominant, brainstem predominant, and cortical α-syn-positive cases. Relationships with age, sex, and ApoE genotype were examined. α-syn co-pathology was detected in 60% of AD cases, more frequently, although not significantly, in women. Half of these positive cases presented α-syn deposits in the cortex, around one-third predominantly in the amygdala, and the remaining cases primarily in the brainstem. A high α-syn load in the amygdala was associated with an increased cortical Aβ load. The cortical tau load was increased in the amygdala-predominant α-syn group, but decreased in the brainstem-predominant and cortical α-syn cases in comparison with α-syn-negative cases. ApoE4 was associated with higher hippocampal α-syn and cortical Aβ deposition. Younger age at death was associated with a focally higher Aβ and tau load. AD cases with cortical α-syn deposition tended to have a younger age at death. Here, we show that next to age, sex, and ApoE genotype, the α-syn distribution in AD is related to different Aβ and tau loads. This may have therapeutic relevance for identifying patients who respond to Aβ immunotherapy related to tau burden and underpin the need to define α-syn pathology and distribution in early disease stages.

Background

Cytosine modifications play critical roles in gene regulation and disease pathogenesis. Elucidating novel epigenetic contributions to Alzheimer’s disease (AD) could advance diagnostic, prognostic, and therapeutic strategies. 5-hydroxymethylcytosine (5hmC), a stable and dynamic DNA modification, has emerging links to AD pathophysiology and potential uses as a biomarker. Cognitive decline, a hallmark of AD progression, varies across individuals and is not fully explained by classic pathological markers. Here, we aimed to develop and validate brain-derived 5hmC-based epigenetic scores to distinguish AD from non-AD pathology and examine their relationship to individual cognitive trajectories.

Methods

Genome-wide 5hmC profiles were generated using 5hmC-Seal and next-generation sequencing on 1016 postmortem human brain prefrontal cortex samples from well-characterized, deceased participants in a longitudinal, clinical-pathologic research study on aging. Samples were processed in independent training and validation sets. Genomic features (e.g., gene bodies, enhancers) were summarized, followed by differential analysis and machine learning-based feature selection to construct classification models distinguishing AD from non-AD.

Results

After quality control and batch correction of 5hmC data, 1005 participants were included, with 655 classified as having AD and 350 as non-AD, according to NIA-AA neuropathologic criteria. In the training set (n = 859), 136 candidate gene bodies and 96 enhancers were selected based on variability and relaxed significance thresholds (p < 0.1). Pathway enrichment analyses implicated cardiovascular function, endocytosis, and MAPK signaling pathways. Using these features, we developed machine learning models that distinguished AD from non-AD with high performance in both the training set (AUC = 87.0%; 95% CI 84.2–89.7%) and validation set (n = 146; AUC = 91.4%; 95% CI 86.6–96.2%). Moreover, the resulting AD-score was significantly associated with rates of global and five domain-specific cognitive decline.

Conclusion

This study extends prior work by translating brain 5hmC profiles into epigenetic scores that distinguish AD pathology and reflect individual cognitive trajectories. These findings highlight the potential of brain-derived 5hmC modifications as biomarkers for AD and as tools to advance research on disease progression, offering a new direction for epigenetics-informed clinical applications in AD.

Parkinson’s disease (PD) pathogenic mutations in leucine-rich repeat kinase 2 (LRRK2) are associated with endolysosomal dysfunction across cell types, and carriers of LRRK2 mutations variably present with phosphorylated tau and α-synuclein deposits in post-mortem analysis. LRRK2 mutations increase the phosphorylation of Rab substrates including Rab12 and Rab10. Rab12 and Rab10 are expressed in neuronal and non-neuronal cells with localization to membranes in the endolysosomal compartment, and lysosomal stress activates LRRK2 phosphorylation of Rabs. In this study, using antibodies directed to the LRRK2-mediated phosphorylation sites on Rab12 at amino acid Ser106 (pS106-Rab12) and Rab10 at amino acid Thr73 (pT73-Rab10), we test whether aberrant LRRK2 phosphorylation is associated with tau and/or α-synuclein pathology across clinically distinct neurodegenerative diseases. Analysis of brain tissue lysates and immunohistochemistry of pathology-susceptible brain regions demonstrate that pS106-Rab12 levels are increased in Alzheimer’s disease (AD) and Lewy body disease (LBD), including PD with and without G2019S LRRK2 mutation. At early pathological stages, phosphorylated Rab12 localizes to granulovacuolar degeneration bodies (GVBs), which are thought to be active lysosomal-like structures, in neurons. pS106-Rab12-positive GVBs accumulate with pathological tau across brain tissues in AD and LBD, and in G2019S LRRK2 mutation carriers. In a mouse model of tauopathy, pS106-Rab12 localizes to GVBs during early tau deposition in an age-dependent manner. While GVBs are largely absent in neurons with mature protein pathology, subsets of both tau and α-synuclein inclusions appear to incorporate pS106-Rab12 at later pathological stages. Further, pS106-Rab12 labels GVBs in neurons and shows co-pathology with tau inclusions in primary tauopathies including Pick’s disease, progressive supranuclear palsy, and corticobasal degeneration. Finally, pT73-Rab10 is elevated and localizes to GVBs, but not tau and α-synuclein inclusions, in AD and LBD, including G2019S LRRK2 mutation carriers. These results implicate LRRK2 kinase activity and Rab phosphorylation in endolysosomal dysfunction in tau- and α-synuclein-associated neurodegenerative diseases.

The autophagy–lysosome pathway (ALP) and the ubiquitin–proteasome system (UPS) are the primary protein degradative mechanisms maintaining proteostasis in neurons. However, the impact of human genetic variation on these pathways and the role of BAG3 are poorly understood, particularly in the context of Alzheimer’s disease, where proteostatic dysfunction is a defining hallmark. We utilized a large panel of iPSCs from deeply phenotyped cohorts to interrogate genetic contributions to baseline autophagic flux and UPS activity in human neurons, and protein turnover was assessed using SILAC-based quantitative proteomics. Across this panel of neurons, we observed substantial inter-individual differences in autophagic flux, which was inversely correlated with UPS activity. This reciprocal relationship extended to tau homeostasis, where higher autophagic flux resulted in reduced accumulation of aggregated, phosphorylated tau. Proteomic analyses revealed that global protein turnover dynamics stratified based on degradation pathway activity and could predict pathway-specific substrate dependencies. Interestingly, Bcl-2-associated athanogene 3 (BAG3), an important member of the chaperone-assisted selective autophagy pathway, emerged as a dynamically regulated autophagy chaperone, responsive to pharmacological inhibition of both the UPS and ALP. BAG3 knockout in neurons decreased autophagic flux and increased levels of high-molecular-weight phosphorylated tau. Notably, familial AD mutations and Aβ exposure induced BAG3 expression in neurons, while elevated BAG3 levels in human brain tissue were associated with higher neuropathological burden and disease progression. Our findings identify BAG3 as a key modulator of proteostasis in human neurons. Its regulation across genetic backgrounds and pathological stimuli suggests a central role in maintaining degradation activities in Alzheimer’s disease and related disorders.

Diffuse midline glioma (DMG; a subtype of pediatric high-grade glioma) is a fatal disease in children, due to the localization in critical structures of the central nervous system, its invasive nature, and limited treatment options. Molecularly, DMG with loss of histone 3 K27 trimethylation (mostly through the typical K27M-mutation in histone 3) have been relatively well characterized, however, no unambiguous Achilles’ heel for targeted therapeutic approaches could be identified to date. This study integrates detailed molecular characteristics of pediatric DMGs with clinical data in a large, international cohort in order to contribute to a better understanding necessary for further development of therapeutic approaches. A total of 162 DMG tumors were analyzed within the INFORM registry from 01/2015 to 11/2023 using comprehensive molecular profiling (including exome, whole-genome and RNA next-generation sequencing approaches, complemented with DNA methylation analysis). Molecular results were correlated with clinical data of the respective patients including the treatment regimen applied and patients’ outcomes. This well-defined cohort of histone 3 K27-altered DMG according to the current WHO classification showed typical molecular alterations for this entity, with differences in frequencies in specific subgroups. The presence of TP53 mutation and the absence of MAPK pathway alteration in the tumors were associated with worse outcomes. In a substantial proportion of patients, genetic alterations serving as targets for potential therapeutic approaches could be identified. This large, international, prospective DMG cohort combines comprehensive molecular characterization of the tumors with registry-level clinical data, thereby contributing to a better understanding of the underlying tumor biology, potential prognostic and predictive markers and the potential impact of targeted therapies.

Primary age-related tauopathy (PART) was proposed in 2014 as a neuropathological term to describe patients with Alzheimer’s-type medial temporal lobe neurofibrillary degeneration in the absence of significant β-amyloid pathology. Over the past decade, this designation has gained widespread adoption, helping to clarify the interpretation of biomarker profiles, delineate early-stage tauopathy in aging, and differentiate non-Alzheimer tauopathies from aging and classical Alzheimer disease. This review revisits PART ten years following its conception, critically evaluating its neuropathological features, clinical correlates, molecular underpinnings, and current limitations. We synthesize recent advances in neuroimaging, biomarkers, genetics, and epidemiology, explore the relationship between PART and other age-associated neurodegenerative processes, and propose revisions to the original PART criteria. While PART has served as a valuable framework for studying tau pathology in aging, key questions remain regarding its pathogenesis, clinical significance, and relationship to the broader spectrum of tauopathies. We highlight major gaps in knowledge and outline priorities for future research aimed at defining the mechanisms, biomarkers, and clinical criteria that will determine whether PART represents a distinct disease or a universal feature of human brain aging.

Tumor-associated macrophages (TAMs) represent the main immune cell population in various brain malignancies, but there is rare knowledge on the functional and, in particular, the prognostic role of TAMs in the meningioma (MGM) microenvironment. Here, we investigated TAM frequencies, activation state, survival-associated changes, and their association with tumor-infiltrating T lymphocytes (TILs) in two independent study samples comprising altogether 680 MGMs. To this end, we performed tissue cytometry analyses, quantified tissue cytokine levels, and integrated previously published TIL infiltration and microarray datasets in the discovery cohort comprising n = 195 clinically well-annotated cases. This was complemented by a DNA methylation-based deconvolution approach to predict TAM and TIL infiltration rates using immune cell-specific CpG sites as well as survival associations in an independent validation cohort of n = 485 MGMs. Our findings revealed substantial but heterogeneous TAM infiltration in newly diagnosed MGMs, with increased numbers of pro-tumoral TAMs in clinically aggressive tumors. Additional cytokine and transcriptome analyses corroborated the presence of an immunosuppressive niche in TAM-enriched MGMs. Importantly, a high frequency of pro-tumoral TAMs was associated with poor patient outcome, and high TAM infiltration was further identified as an independent prognostic factor for inferior survival, counteracting the beneficial prognostic effect of TILs. Moreover, methylation-based deconvolution analyses confirmed the opposing prognostic roles of TAMs and TILs in the validation cohort. Altogether, higher numbers of TAMs appear to be a hallmark of clinically aggressive behavior in newly diagnosed and recurrent MGMs. Unlike TILs, immunosuppressive TAMs seem to play a dominant role in the immunological landscape of MGMs with a significant negative impact on patient outcome, highlighting pro-tumoral TAMs to be an attractive treatment target in MGMs. Furthermore, our deconvolution approach presents a pipeline to computationally determine TAM and TIL infiltrates in the MGM microenvironment, which might be highly valuable for patient stratification for future immunotherapeutic treatments.

Disturbances within the cerebrovascular system substantially contribute to the pathogenesis of age-related cognitive impairment and Alzheimer’s disease (AD). Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid-β (Aβ) in the leptomeningeal and cortical arteries and is highly prevalent in AD, affecting over 90% of cases. While the ε4 allele of apolipoprotein E (APOE) represents the strongest genetic risk factor for AD, it is also associated with cerebrovascular dysregulations. APOE plays a crucial role in brain lipid transport, particularly in the trafficking of cholesterol and phospholipids. Lipid metabolism is increasingly recognized as a critical factor in AD pathogenesis. However, the precise mechanism by which APOE influences cerebrovascular lipid signatures in AD brains remains unclear. In this study, we conducted non-targeted lipidomics on cerebral vessels isolated from the middle temporal cortex of 89 postmortem human AD brains, representing varying degrees of CAA and different APOE genotypes: APOE ε2/ε3 (N = 9), APOE ε2/ε4 (N = 14), APOE ε3/ε3 (N = 21), APOE ε3/ε4 (N = 23), and APOE ε4/ε4 (N = 22). Lipidomics detected 10 major lipid classes with phosphatidylcholine (PC) and phosphatidylethanolamine (PE) being the most abundant lipid species. While we observed a positive association between age and total acyl-carnitine (CAR) levels (p = 0.0008), the levels of specific CAR subclasses were influenced by the APOE ε4 allele. Notably, APOE ε4 was associated with increased PE (p = 0.049) and decreased sphingomyelin (SM) levels (p = 0.028) in the cerebrovasculature. Furthermore, cerebrovascular Aβ40 and Aβ42 levels showed associations with sphingolipid levels including SM (p = 0.0079) and ceramide (CER) (p = 0.024). Weighted correlation network analysis revealed correlations between total tau and phosphorylated tau and lipid clusters enriched for PE plasmalogen and lysoglycerophospholipids. Taken together, our results suggest that cerebrovascular lipidomic profiles offer novel insights into the pathogenic mechanisms of AD, with specific lipid alterations potentially serving as biomarkers or therapeutic targets for AD.