Acta Neuropathologica Communications最新文献

Focal cortical dysplasia (FCD) is a common malformation of cortical development and a major cause of early-onset, drug-resistant epilepsy. FCD type II is defined by abnormal lamination, altered cellular composition, and pathological cells, notably dysmorphic neurons (DNs) and balloon cells. DNs are thought to drive epileptogenicity through both cell-autonomous and non-cell-autonomous mechanisms, the latter including not only aberrant connectivity but also indirect modulation of excitability in local cell populations. We performed a multiscale structural and morphological analysis to elucidate the basis of FCD epileptogenicity and the impact of somatic mTOR mutations during brain development. Using a mouse model of FCD type II, we show that lesions in frontal and motor cortical regions are the strongest predictors of spontaneous seizure occurrence. This localization-dependent epileptogenicity offers an experimental explanation for the higher clinical epileptogenicity of frontal FCDs and suggests that posterior lesions may remain silent-an open question in human pathology. In our model, FCD tissue displayed considerable expansion, with cortical thickness up to ~ 20% in seizure-bearing animals. This expansion coincided with an overall ~ 40% reduction in neuronal density, consistent with tissue hypertrophy. DN density did not differ between seizure and non-seizure animals, challenging the notion that higher DN load directly predicts epileptogenesis. At the microscopic level, we describe DN axonal pathologies, including giant varicosities. In the cortex, these appeared as vesicle-filled boutons, whereas along callosal axons they were frequent but largely empty. Bouton density was markedly reduced in FCD cortex. Together, these findings leave the net synaptic effect of dysmorphic neurons unresolved, challenging the assumption that axonal hypertrophy translates into increased excitatory drive. While morphological abnormalities in FCD type II are well documented, their functional consequences remain incompletely understood. Here, we used macro- and microscopic structural features of FCDII to assess seizure susceptibility, providing new insights into epileptogenesis.

Background: Huntington's disease (HD) is the most frequent autosomal dominant neurodegenerative disorder, which is caused by a CAG repeat expansion in the HTT gene. Despite its well-defined genetic origin, there is currently no cure, and reliable biomarkers for disease progression and pathophysiology remain limited. Mutant huntingtin protein accumulates in endosomal compartments, disrupting endosomal trafficking and potentially affecting the biogenesis, release, and cargo of exosomes-extracellular vesicles (EVs) derived from the endosomal pathway. However, the role of exosomes in HD pathogenesis and their potential as biomarkers has been underexplored. In this work, we investigated whether the levels and content of small EV subpopulations, including exosomes, are altered in the brains of HD patients.

Methods: We analyzed two distinct subpopulations of small EVs from the striatum and cortex of postmortem HD brains at early and advanced neuropathological stages, as well as from age-matched controls. EVs were isolated by differential ultracentrifugation and high-resolution iodixanol density gradient centrifugation, and analyzed by Western blotting, electron microscopy, NTA, and proteomics using mass spectrometry. EV secretion was also analyzed in primary fibroblasts derived from HD patients and healthy controls.

Results: Mass spectrometry data revealed HD-associated alterations in EV protein content, particularly proteins related to the endosomal system. Our data also indicate that the level of ectosomes increased in the HD cortex, whereas exosomes were reduced in the HD striatum compared to controls. In terms of EV content, EVs from HD brains showed increased levels of Annexin A2 and decreased levels of Alix, a key component of the endosomal sorting complex required for transport (ESCRT). Alix depletion in EVs mirrored a progressive reduction of Alix in brain tissue, correlating with disease severity based on Vonsattel staging. In vitro, HD fibroblasts secreted EVs with reduced Alix content, despite no significant difference in cellular Alix levels compared to controls.

Conclusions: These findings highlight disease-specific changes in EV populations and cargo in HD, and identify Alix as a potential neuropathological marker. This study advances our understanding of the role of brain-derived EVs in HD and underscores their potential utility in biomarker discovery.

The spectrum of frontotemporal dementia/amyotrophic lateral sclerosis (FTD/ALS) and Huntington disease (HD) are fatal neurodegenerative disorders with no major disease-modifying therapies. Recent work has shown that the hallmark pathological proteins TAR DNA binding protein of 43 kDa (TDP-43) in FTD/ALS and mutant huntingtin (mHTT) in HD may be interlinked. Furthermore, these disorders share early features of altered metabolism and psychiatric symptoms that have been suggested to arise from pathology in the hypothalamus, an important brain region involved in the regulation of metabolism and emotions. Agouti-related protein (AgRP)-expressing neurons localised exclusively to the arcuate nucleus (ARC) of the hypothalamus are key modulators of body weight regulation and food seeking behaviour, and they have recently been implicated in anxiety- and anhedonic-like processes. The aim of this study was to investigate the effects of overexpression of TDP-43 or mHTT in AgRP-expressing neurons on metabolic, behavioral and neuropathological features in mice. Flex-switch adeno associated viral vectors expressing human wild-type TDP-43, mHTT or green fluorescent protein to serve as a control, were injected into male and female AgRP-Cre mice to target the ARC using stereotactic surgery. We demonstrate targeted overexpression of transgenes including formation of mHTT inclusions in the ARC of the hypothalamus. Overexpression of mHTT led to a significant reduction in AgRP fibres in the hypothalamus 21 weeks post-injection, as well as higher food consumption in female mice. Overexpression of TDP-43 did not lead to the development of any metabolic or behavioral phenotypes in the mice. Our data suggest that AgRP neurons in the ARC are protected from the toxic effects resulting from overexpression of TDP-43 whereas they display some sensitivity to mHTT overexpression resulting in mHTT inclusion formation, reduction in AgRP fibers and sex-specific effects on food consumption. Taken together, other hypothalamic neuronal populations may be more important for the development of non-motor features resulting from overexpression of TDP-43 and mHTT in the hypothalamus.

Background: Down syndrome (DS), or trisomy 21 (T21), resulting from an extra copy of chromosome 21, occurs in 1 in 700-1,000 live births. Neuroinflammation is increasingly recognized as a critical contributor to DS neuropathology, although its underlying drivers remain unclear.

Methods: In this study, we analyzed available single-nucleus RNA sequencing (snRNAseq) data from postmortem cortical brains of individuals with DS and controls aged 36 years or younger, focusing specifically on astrocyte-enriched clusters. This analysis revealed significant alterations in complement system gene sets. To further investigate these findings, we employed a human in vitro model using astrocytes differentiated from urine-derived induced pluripotent stem cells (iPSCs) obtained from individuals with DS (T21-iPSCs). To our knowledge, this is the first study to evaluate both gene expression and protein levels of secreted complement components in T21-iPSC-derived astrocytes.

Results: snRNAseq re-analyzes identified an upregulation of complement system components, including C1R, C1S, C2, C4A, C4B, C5, C5AR1, C6, C8, CD59, CFI, and FCN2, and of glutamate transporters SLC1A3 (EAAT1/GLAST-1) and SLC1A2 (EAAT2/GLT-1) in DS astrocytes. Results from the in vitro model revealed distinct phenotypic changes in T21-iPSC-derived astrocytes, including enlarged cell and nuclear sizes, and enhanced glutamate uptake. Elevated levels of C5aR1 and MASP1 transcripts, as well as increased C4 protein secretion in culture supernatants, suggest dysregulation of the complement system in DS.

Conclusions: These findings highlight the potential contribution of astrocyte-driven complement signaling to DS neuropathogenesis. While further validation is needed, this work points to a candidate pathway that may serve as a target for future therapeutic investigation to improve the quality of life for individuals with DS.

Alcohol use disorders (AUD) is one of the most prevalent mental disorders in the United States affecting more than 10% of the adult population. Cerebellar atrophy and Purkinje cell (PC) degeneration are frequently observed in patients with AUD. Alcohol can cause endoplasmic reticulum (ER) stress in PCs and alter PC structure and function. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an ER stress inducible protein highly expressed in PCs. It is neuroprotective in various ER stress-related pathological conditions. However, it is unknown whether MANF plays a role in protecting PCs from alcohol-induced ER stress and neurodegeneration. In this study, we generated PC-specific MANF knockout (KO) mouse model to test the hypothesis that MANF-deficient PCs are more susceptible to alcohol-induced ER stress and neurodegeneration in the adult brain. We employed a binge alcohol exposure paradigm and tested the effect of alcohol and MANF deficiency on molecular, cellular, and behavioral outcomes in the adult animals. We also performed spatial transcriptomics and high throughput in situ analyses to profile gene expression changes in response to MANF deficiency. We found that alcohol exacerbated the motor function deficits in PC-specific MANF KO animals. Interestingly, female KOs were more sensitive to alcohol-induced motor function impairments than male KOs. In accordance with the behavior changes, alcohol exposure activated the unfolded protein response (UPR), increased intranuclear expression of calcium binding protein, and caused PC degeneration in female but not male MANF KO mice. Spatial transcriptomics and high throughput Xenium in situ analyses revealed that MANF deficiency altered the transcriptomic landscape in PCs in a sex-specific manner and triggered the expression of genes involved in protein folding and transportation, and response to ER stress. Our study reveals that MANF-deficient PCs are predisposed with a higher risk to UPR activation and disrupted calcium homeostasis in a sex-dependent manner, which may underline their sex-specific vulnerability to alcohol-induced neurodegeneration. These findings suggest that ER stress plays a significant role in alcohol-triggered neurodegenerative process in the cerebellum, and MANF may possess therapeutic potentials in AUD via its capacity in restoring ER and calcium homeostasis.

Significant advances over the last two decades in the study of in vitro prion formation and propagation have revealed that distinct cofactors can facilitate or induce spontaneous prion misfolding. This, in turn, has raised important questions about the role of cofactors and their potential significance in vivo in prion diseases. Key questions include whether cofactors are necessary for prion infectivity or whether they might play a crucial role in determining strain features without being essential for infection. Grounded in previous work that showed that polyanions such as RNA or dextran sulfate facilitate spontaneous prion misfolding in vitro, we have addressed whether other chemically similar cofactors could expand the diversity of PrP^Sc conformers and whether these would exhibit distinctive strain features. Using the Protein Misfolding Shaking Amplification (PMSA) and three different polyanionic cofactors (heparin, chondroitin sulfate and pentosan polysulfate), we obtained and characterized a total of nine conformers and compared them to previously generated strains obtained with dextran sulfate. All nine conformers proved infectious in transgenic mice, generating distinct prion strains and suggesting that different cofactors can indeed drive the formation of distinct conformers. However, the observed variations within conformers generated with the same cofactor indicate a degree of structural flexibility, likely resulting in related but distinguishable groups of conformers. Our study demonstrates that sulfated glycans not only facilitate in vitro spontaneous PrP^Sc generation but also enable the emergence of multiple distinct prion strains, providing insights into the molecular mechanisms underlying strain diversity and their potential relevance to spontaneous prion diseases.

Parkinson's disease (PD) is defined by the progressive loss of dopaminergic neurons and the accumulation of misfolded α-synuclein (α-syn), yet the molecular determinants of selective neuronal vulnerability remain unresolved. Increasing evidence implicates mitochondria-and particularly their membranes-as critical platforms where α-syn is toxic. This review highlights how α-syn engages mitochondrial membranes through two interconnected processes: classical aggregation and liquid‒liquid phase separation. Both pathways disrupt membrane architecture, compromise respiratory chain function, and impair mitophagy. A pivotal mediator of these events is cardiolipin (CL), a mitochondria-specific phospholipid essential for cristae organization and quality control pathways. Despite extensive progress, the precise mechanistic contributions of CL to α-syn aggregation, phase transitions, and neuronal degeneration remain poorly defined. Clarifying this interplay is crucial, as CL not only binds α-syn with high affinity but also determines whether it remains in a functional state or progresses toward toxic assemblies. By integrating recent advances, we propose a unifying perspective on CL as a molecular switch at the crossroads of mitochondrial biology, protein aggregation, and phase behavior. Beyond mechanistic insight, this view underscores the potential of CL as a target for the development of mitochondria-directed therapies in PD.