Acta Neuropathologica最新文献

Alzheimer’s disease is the most common form of dementia; however, its molecular mechanisms are not fully understood. We recently identified polymeric glycine–arginine-containing (polyGR+) aggregates as a novel type of proteinopathy in AD autopsy brains. Here, we performed a comprehensive analysis to study if polyGR+ aggregates are associated with AD neuropathological changes (ADNC) and clinical features of AD cases. We show polyGR+ aggregates are detected in ~ 60% of AD postmortem brains from three AD cohorts but not age-similar controls or disease controls with primary age-related tauopathy (PART). A subtype of polyGR+ aggregates with a clustered-punctate morphology that is positive for the markers of dystrophic neurites is associated with earlier onset and shortened survival in AD cases. Increased levels of Aβ plaques and phosphorylated tau (pTau) tangles are detected in the hippocampus of AD autopsy brains with high levels of polyGR+ aggregates compared to AD autopsy brains with minimal polyGR+ staining. In addition to ADNC, a subset of polyGR+ aggregates coexists with limbic-predominant age-related TDP-43 encephalopathy neuropathological changes (LATE-NC) or Lewy body pathology (LBP). Hippocampal polyGR+ aggregate levels are ~ 3.8- and ~ 3.71-fold higher in late-onset AD cases who experienced stroke or high blood pressure, respectively. In SH-SY5Y cells, hydrogen peroxide treatment which mimics oxidative stress leads to increased levels of polyGR+ proteins produced by the CASP8 GGGAGA repeat expansion, which was recently shown to associate with increased AD risk. In addition, we show the accumulation of pTau induced by CASP8 polyGR+ protein aggregates is elevated upon hydrogen peroxide treatment. In summary, our results demonstrate polyGR+ aggregates are a frequent and understudied type of proteinopathy in AD autopsy brains and that polyGR proteinopathy is associated with ADNC.

In synucleinopathies, the protein α-synuclein misfolds into Lewy bodies (LBs) in patients with Lewy body disease (LBD) or into glial cytoplasmic inclusions (GCIs) in patients with multiple system atrophy (MSA). The ability of a single misfolded protein to cause disparate diseases is explained by the prion strain hypothesis, which argues that protein conformation is a major determinant of disease. We recently reported the unexpected finding of a novel α-synuclein strain in a Parkinson’s disease with dementia patient sample containing GCI-like co-pathology along with widespread LB pathology, which led us to question if two α-synuclein strains can interact with one another in a patient and, if so, can strain competition occur. To test this possibility, we used the strain interference model developed in the prion field, in which a slower replicating strain—in this study, mouse-passaged MSA—is used to compete with a faster replicating strain—here, recombinant preformed fibrils (PFFs)—following sciatic nerve (sc.n.) inoculation. Unexpectedly, we found that PFFs generated using the same method differed in their ability to neuroinvade following sc.n. inoculation based on α-synuclein monomer source. Using a PFF preparation that does spread from the periphery, we conducted strain competition studies by first injecting TgM83^+/− mice with mouse-passaged MSA into the sc.n. followed by a second injection with PFFs at 30, 45, and 60% of the MSA incubation period. We found that the two α-synuclein strains exhibited a synergistic effect during neuroinvasion, which was characterized by a decrease in incubation period along with evidence of the mouse-passaged MSA strain in the brain of terminal animals. These findings indicate that two α-synuclein strains can synergize with one another to accelerate the progression of clinical disease, representing a novel outcome in mixed infection studies.

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.