Acta Neuropathologica最新文献

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas and a major cause of mortality in neurofibromatosis type 1 (NF-1). Distinguishing MPNSTs from benign neurofibromas remains challenging. We investigated fibroblast activation protein alpha (FAP) as a malignancy biomarker and theranostic target in peripheral nerve sheath tumors. Therefore, we integrated publicly available bulk transcriptomics, spatial transcriptomics, and single-cell RNA sequencing with immunohistochemistry (IHC) on independent archival samples. We further directly assessed clinical translatability using FAP-targeted PET/CT in an NF-1 patient undergoing work-up for suspected malignant transformation. Across independent bulk datasets, FAP was consistently up-regulated in MPNSTs compared with neurofibromas. In the TCGA sarcoma dataset, FAP varied by histotype but was clearly expressed in MPNSTs. Spatial transcriptomics revealed enrichment of FAP-high regions in MPNSTs and co-localization with tumor cell markers. Single-cell analysis showed FAP expression in MPNST tumor cells and cancer-associated fibroblasts, with the highest levels in neural crest-like tumor subpopulations previously linked to adverse prognosis; pseudotime analysis indicated decreasing FAP expression along trajectories toward Schwann cell precursor-like states linking FAP expression to a more primitive, dedifferentiated tumor cell state. IHC confirmed strong, predominantly tumor cell-intrinsic FAP expression in MPNSTs, with minimal staining in neurofibromas and normal tissues. Plexiform neurofibromas exhibited intermediate FAP expression. In clinical imaging, FAP-PET demonstrated higher tracer uptake in histologically proven MPNSTs than in benign lesions within the same patient, including a neurofibroma that was FDG-avid but FAP-negative, supporting added diagnostic specificity over FDG-PET/CT. In summary, FAP is robustly overexpressed in MPNSTs at transcript and protein levels, potentially concentrates in high-risk tumor cell states, and is detectable by targeted PET imaging. These findings identify FAP as a clinically relevant biomarker for malignancy in NF-1-associated tumors and support implementation of FAP-directed diagnostics and therapeutics in peripheral nerve sheath tumor work-up.

Lewy body dementia (LBD), encompassing dementia with Lewy bodies and Parkinson’s disease dementia, is neuropathologically defined by neuronal accumulation of α-synuclein encoded by the SNCA gene. Genetic risk factors strongly influence LBD susceptibility, including SNCA multiplication, particularly triplication, and the apolipoprotein E ε4 allele (APOE4), the strongest common genetic risk factor for LBD. While SNCA is predominantly expressed in neurons and APOE primarily in glial cells, how these genetic factors converge to impact neuronal vulnerability and regional pathology in the human brain remains poorly understood. Here, we applied spatial transcriptomics to postmortem temporal cortex tissue from LBD cases with SNCA triplication or different APOE genotypes, alongside age- and sex-matched controls, to map gene expression within intact cortical architecture. We identified layer 5 of the gray matter as a particularly vulnerable region, characterized by elevated SNCA expression, pronounced synaptic and metabolic dysregulation, and exacerbation of these alterations in APOE4 carriers. Reelin signaling emerged as a core Lewy body-associated pathway disrupted across cortical layers, validated in independent postmortem cohorts and human-induced pluripotent stem cell (iPSC)-derived cortical organoids. In contrast, white matter exhibited distinct molecular alterations, including disrupted myelination pathways, with APOE4 carriers showing increased myelin debris and glial responses compared with non-carriers. Cell-type deconvolution informed by single-nucleus RNA sequencing further revealed APOE4-associated impairments in neuronal vulnerability and intercellular communication. Together, these findings define spatially and cell-type-specific mechanisms through which SNCA dosage and APOE4 genotype impact LBD pathology, providing insight into regionally distinct disease processes and potential targets for genetically stratified therapeutic interventions.

Multiple system atrophy (MSA) is a fatal neurodegenerative synucleinopathy characterized by the accumulation of α-synuclein in oligodendrocytes, forming glial cytoplasmic inclusions. Although iron dysregulation and ferroptosis, an iron-dependent form of regulated cell death, have been implicated in neurodegeneration, their specific role in MSA oligodendrocytes remains unknown. We investigated ferroptosis pathways in postmortem brain tissues from patients with MSA, Parkinson’s disease (PD), and healthy controls (HCs) by immunofluorescence for GPX4 co-labelled with CNPase (oligodendrocyte marker) or TH (dopaminergic neuron marker). To validate these findings, we employed PLP-hαSyn transgenic mice, an established MSA model, and the human oligodendrocytic cell line MO3.13, subjected to α-synuclein over-expression, preformed fibrils (PFF) exposure, and brain homogenates derived from MSA pons. Mechanistic insights were pursued through immunofluorescence, JC-1, FerroOrange, western blotting, and co-immunoprecipitation. Finally, we developed a novel biomarker assay using nanoscale flow cytometry to quantify FTH1-containing, CNPase-positive (oligodendrocyte-derived) EVs (ODFC-EVs) in plasma samples from 49 MSA patients, 46 PD patients, and 48 HCs. GPX4, the key ferroptosis regulator, was significantly reduced in CNPase⁺ oligodendrocytes of MSA brains versus PD and HCs, while, as expected, GPX4 loss in PD predominated in TH⁺ neurons. PLP-hαSyn mice recapitulated the unique GPX4 suppression in oligodendrocytes. In MO3.13 cells, α-synuclein enhanced erastin-induced GPX4 loss, increased labile Fe²⁺ accumulation and aggravated mitochondrial depolarisation. Mechanistically, α-synuclein was found to directly bind and stabilize NCOA4, impairing its ubiquitination-mediated degradation. This enhanced NCOA4 activity drove excessive ferritinophagy, leading to the lysosomal degradation of the iron-storage protein FTH1 and subsequent iron overload. Translationally, plasma levels of ODFC-EVs were significantly reduced in MSA patients compared to both PD patients (AUC 0.771; sensitivity 65.3%, specificity 84.8%) and HCs (AUC 0.857; sensitivity 67.4%, specificity 91.7%). Our study provides the first in vivo and mechanistic evidence supporting a model in which α-synuclein drives oligodendrocyte-specific ferroptosis in MSA by stabilizing NCOA4, depleting FTH1 and promoting toxic iron accumulation. This cell-type-restricted mechanism distinguishes MSA pathogenesis from that of PD. Furthermore, the parallel reduction of circulating ODFC-EVs offers a readily accessible blood-based biomarker to discriminate MSA from PD. Together, these findings position the α-synuclein-NCOA4-FTH1 axis as a central pathogenic pathway and a compelling therapeutic target for MSA.

Lobar intracerebral haemorrhage (ICH) is associated with cerebral amyloid angiopathy (CAA) pathology. Uncertainty remains about the mechanisms leading from CAA to ICH. We investigated the distribution and characteristics of CAA, and its clinical and neuropathological associations. Participants underwent research autopsy in the Lothian IntraCerebral Haemorrhage, Pathology, Imaging and Neurological Outcome (LINCHPIN) study. Neuropathologists rated tissue for CAA using standardised consensus criteria, as well as non-amyloid small vessel disease, Thal phase, and Braak stage. We compared the presence, distribution, and severity of CAA among different brain regions, and in the lobe or hemisphere affected by lobar ICH to corresponding contralateral regions. We evaluated the diagnostic accuracy of Vonsattel CAA grade on a post-mortem cortical specimen (simulating surgical biopsy) versus the reference standard of moderate-to-severe parenchymal CAA at autopsy. Among 162 participants, parenchymal CAA, meningeal CAA, and CAA-associated vasculopathy were diffusely distributed among all cerebral lobes irrespective of the ICH location, but capillary CAA showed an occipital predominance. In lobar ICH, all CAA measures did not differ between the ICH lobe or hemisphere and the contralateral unaffected region. CAA measures did not increase with age, but they were higher in carriers of APOE ε2 or ε4 alleles and in individuals with higher Thal phase or Braak stage. Using a rule-out category of Vonsattel grade ≥ 1 to diagnose CAA on a simulated cortical biopsy achieved 100% sensitivity (95%CI 93.4–100), and a rule-in category of Vonsattel grade ≥ 2 had 79.5% specificity (95%CI 63.5–90.7) versus the reference standard. The distribution and severity of parenchymal CAA, meningeal CAA, and CAA-associated vasculopathy are diffuse regardless of ICH location, indicating the need to better understand the factors underlying bleeding in CAA-affected vessels.

Alzheimer’s disease (AD) is phenotypically characterised by progressive memory loss, which has been linked to tau aggregation and synaptic dysfunction. Here we characterised the nanoscopic tau aggregates in individual synaptosomes from AD cases and controls, measuring their number and size using SynPull with direct stochastic optical reconstruction microscopy (dSTORM). A total of 7888 synaptosomes from pre-frontal cortex samples were studied, showing the presence of AT8-positive tau aggregates in a small fraction of synaptosomes (~ 3%) from control brains, reaching ~ 20% by Braak stage 6. These key findings of the intra-synaptic localisation of aggregates and existence of synaptic tau pathology at Braak stage 3—preceding tangle formation in this region, were confirmed using aggregate-specific single-molecule array (SIMOA) with proteinase K digestion, three-dimensional super-resolution microscopy, stimulated emission depletion microscopy (STED), and immunohistochemistry. The aggregates also grew in size with AD progression with an average length of 117 nm at stage 0, 154 nm at stage 3 and 182 nm at stage 6, however they mostly remained non-elongated (circular) with average eccentricity values remaining below 0.8. We then investigated the multi-phosphorylation of synaptic tau aggregates for AT8 and T181 and quantified their co-localisation with phosphatidylserine and CD47, synaptic “eat me” and “don’t eat me” signals respectively, along with synaptogyrin-3, which contributes to tau-mediated synaptic dysfunction. T181, phosphatidylserine, and synaptogyrin-3 co-localisation with AT8-positive tau were higher during stage 3 and CD47 was lower, indicating early synaptic pathology is associated with the formation of small tau aggregates, contributing to microglia-driven synaptic loss.

Familial occurrence of gliomas has been reported in around 5% of patients. Studies on the genetic landscape of glioma predisposition are scarce. Here, leukocyte DNA of 213 adult glioma patients with a familial and/or personal tumor history from 206 families was subjected to whole-exome sequencing. Germline variants (GVs) were analyzed using two approaches: (1) GVs in 164 established cancer predisposition genes (CPGs) or suspected glioma risk genes were extracted and classified; (2) the enrichment of genes with loss-of-function or deleterious missense GVs that were ultrarare or ClinVar likely pathogenic/pathogenic in the glioma versus a control cohort (n = 391) was determined. In 23% (48/213) of glioma patients with a familial/personal tumor history, GVs predicted to be deleterious in CPGs were detected. Of the mutated CPGs, 37% were involved in DNA damage response, including ATM, BRCA2, PMS2, POLE. ATM GVs (n = 6) preferentially predisposed to IDH-mutant astrocytoma (P = 0.007) in patients that were significantly younger at diagnosis than patients without GVs (P = 0.022). BRCA2 GVs (n = 5) were also significantly enriched in glioma patients in approach 2 (P = 0.005). The other mutated CPGs, glioma risk or enriched novel genes play roles in diverse processes, including metabolism and signal transduction. Syn-/metachronous non-brain tumors were diagnosed in 29% of glioma patients with GVs. In 11% of patients, the identified CPG GVs potentially sensitized to targeted therapies, such as PARP, immune checkpoint, or EGFR inhibitors. In conclusion, our study identifies CPGs and novel genes relevant in germline testing of glioma patients with a familial/personal tumor history, possibly resulting in targeted treatment options.

Creutzfeldt-Jakob disease (CJD), the most common human prion disease, is an invariably fatal neurodegenerative disorder affecting 1.5 cases per million individuals per year. About 10–15% of the human prion diseases are caused by a pathogenic variant in the prion protein (PrP) gene (PRNP), and the most common genetic human prion disease is CJD (gCJD) linked to a glutamic acid to lysine substitution at codon 200 (E200K) of PRNP. The polymorphic codon 129 methionine (M)/valine (V) genotype has a strong effect on disease phenotype. In the present study, we retrospectively evaluated many features of gCJD E200K cases with respect to the 129MV polymorphism, type of scrapie prion protein (PrP^Sc), demographic, clinical, laboratory, histopathology, and molecular features, including western blot examination and real-time quaking-induced conversion assay. Analyses were also performed to determine statistically significant features between E200K haplotypes (e.g., codon 129 genotype in cis with the mutated allele) and codon 129 genotypes. This study found that codon 129 polymorphism affects several disease features of gCJD E200K. Specifically, histopathologic differences were found between patients with different 129 haplotypes and genotypes. We have identified five groups or subtypes of E200K associated with either PrP^Sc type 1 or 2. Other E200K cases showed mixed (i) PrP^Sc types or (ii) pathological features of 129 M and 129 V haplotypes. To our knowledge, this study describes the largest cohort of 177 E200K cases and provides new insight into the wide range of phenotypes associated with this common CJD genetic variant.

Synucleinopathies, including Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA), share pathological accumulation of misfolded α-synuclein (αSyn) in the brain and overlapping clinical features, complicating accurate diagnosis with current methods. In this study, we utilized a real-time quaking-induced conversion (RT-QuIC) assay to demonstrate that autopsied skin samples from PD, DLB, and MSA patients (but not non-synucleinopathy controls) seed aggregation of recombinant αSyn. While RT-QuIC generated similarly positive fluorescence kinetic curves across synucleinopathies, biochemical and morphological analyses of RT-QuIC end products revealed distinct properties in the resulting αSyn aggregates. Notably, αSyn aggregates from DLB samples exhibited the highest resistance to proteinase K digestion, whereas MSA-derived aggregates showed the least aggregated bands on Western blots. Transmission electron microscopy revealed significant differences in length, width, and volume of skin αSyn fibrils of RT-QuIC end products from different synucleinopathies. These findings provide critical insights into disease-specific αSyn structural characteristics and suggest new strategies to improve diagnostic discrimination.

Essential tremor (ET), among the most common movement disorders, is characterized by 8–12 Hz action tremor of the upper extremities. Cognitive dysfunction is increasingly recognized. Postmortem studies of anterior cerebellar cortex, which plays a major role in motor function, have systematically identified morphologic changes centered on Purkinje cells (PCs) and adjacent neuronal connections, distinguishing ET from controls. However, the cerebellar cortex is compartmentalized into distinct functional anatomic regions, including control of cognition in posterior lobe. No systematic study of this posterior region has been undertaken in ET. Leveraging resources of the Essential Tremor Centralized Brain Repository, we compared the pathology across anterior and posterior hemispheric cerebellar cortices in each brain in a postmortem series of 123 brains in ET (n = 80) and controls (n = 43). We used 11 quantitative morphologic metrics that reflected PC loss, heterotopic PCs, PC dendritic changes, PC axonal changes (torpedoes, torpedo-associated and non-torpedo related), basket cell axonal hypertrophy, and climbing fiber-PC puncta changes. These metrics distinguished ET cases from controls in both anterior (11/11 metrics) and posterior regions (10/11 metrics) (p values 0.045 to < 0.0001), and 10/11 metrics demonstrated a greater burden of pathology in the ET anterior versus ET posterior cerebellar region (p values 0.045 to < 0.0001). Regional differences among controls were present to a lesser extent than in ET (6/11 metrics; p values 0.035 to < 0.0001). In a principal component analysis, these combined metrics segregated control and ET cases according to both diagnosis and cerebellar region. This is the first study to carefully document that pathology in the ET cerebellum extends beyond the anterior cerebellar region to also involve a posterior cerebellar region. In line with the prominent motor features of ET, the burden of cerebellar pathology was greater in the anterior region. These results advance our nascent understanding of the underlying neuropathological substrate of this highly prevalent disease.