Acta Neuropathologica

Parkinsons disease is defined clinically by motor dysfunction, but its pathology is not confined to nigral dopaminergic neurons. Prominent non-motor features including cognitive impairment, autonomic failure and sleep disturbance indicate widespread neurodegeneration that remains incompletely characterised. We pre-registered and conducted a multilevel meta-analysis of 166 case-control post-mortem studies published between 1963 and 2025, mapping neuronal loss across 85 brain regions, 38 cell types and 145 region-cell populations. The evidence base behind this map is thin. Only 4 of 145 populations are adequately powered, and 82% of Allen Brain Atlas regions have never been quantified in Parkinsons disease. A further 18 populations would reach adequate power with five or fewer additional studies, identifying an efficient route to closing current gaps. Noradrenergic neurons of the locus coeruleus degenerate to a similar extent as substantia nigra dopaminergic neurons, with both populations losing more than 60% of neurons. Cholinergic neurons of the basal nucleus and pedunculopontine tegmental nucleus and dopaminergic neurons of the ventral tegmental area show significant but less severe loss. These findings establish Parkinsons disease as a multi-system neurodegenerative disorder and expose key gaps and biases in the existing literature.

Despite growing evidence for glial involvement in Parkinsons disease, oligodendrocyte dysfunction remains poorly defined. To address this gap, we compared single-cell RNA sequencing from a mouse model of -synuclein aggregation pathology with fresh human brain tissue from deep brain stimulation surgery to build a cross-species framework of disease progression. In total, we profiled over 200,000 cortical transcriptomes, including 55,000 oligodendrocytes. Early disease in mice was characterized by inflammatory activation, while advanced stages in both species converged on metabolic dysfunction, including impaired ribosomal output, chaperone stress responses, ubiquitination deficits, and lysosomal perturbation. In patients, APLP1 was upregulated and correlated with clinical disease progression and increased levodopa demand, linking -synuclein spread in oligodendrocytes to disease severity. APP and CNTN pathways emerged as key signalling axes, with CNTN reflecting weakened reparative communication and reduced resilience. Together, these findings define oligodendrocyte subtype dynamics as shared and clinically relevant features of PD progression.

-Synuclein nitration is a prominent post-translational modification in Parkinsons disease, but whether nitrated -synuclein merely reflects oxidative stress or actively contributes to pathology remains unclear. Here, we generated and characterized 6G6, an antibody selective for Tyr39-nitrated -synuclein, and tested whether targeting this modified -synuclein species affected pathology in different mouse models of -synuclein aggregation and spread. In two models of -synuclein overexpression targeting medullary vagal neurons, oxidative stress was induced by either exposure to the herbicide paraquat or transgenic heterozygous expression of the Gba1-L444P mutation. Both conditions were characterized by robust -synuclein spreading that was markedly counteracted by 6G6 administration. A third model consisted of an injection of -synuclein fibrils into the striatum of -synuclein-overexpressing mice. In this model, treatment with 6G6 protected against fibril-induced aggregate pathology and ensuing degeneration of nigral dopaminergic neurons. In a pilot human study, CSF levels of Tyr39-nitrated -synuclein were measured and found increased in Parkinson patients as compared to controls. These findings identify Tyr39-nitrated -synuclein as a pathogenic, therapeutically targetable -synuclein species linking oxidative/nitrative stress to PD pathological processes.

Retrospective studies in patients with non-muscle invasive bladder cancer (NMIBC) have reported a significant reduction in Alzheimers disease (AD) incidence (12-78%) among Bacillus Calmette-Guerin (BCG) recipients versus controls. To investigate the underlying mechanisms, we evaluated BCG in the PS19 mouse model of tauopathy. We found that BCG administration reduced hippocampal phospho-tau and microgliosis while preserving neuronal markers. In vivo volumetric T2-MRI demonstrated attenuation of brain atrophy accompanied by increased glutamate-weighted CEST-MRI signals. Functionally, BCG-treated mice showed improved performance in the novel object recognition test (NORT), as well as improved body-weight maintenance and survival. Transcriptomic profiling of the hippocampus revealed near complete normalization of the PS19 disease-associated gene expression signature towards that of healthy controls. Flow cytometric profiling of brain myeloid populations demonstrated a reduction in activated resident microglia, but total microglia cells remain elevated. Moreover, an increase of the co-stimulatory marker CD80 on the recruited peripheral myeloid cells ensues following BCG treatment. Consistent with this shift in myeloid state, primary brain myeloid cells from BCG-treated mice also exhibited enhanced phagocytosis of FITC-labeled tau fibrils and increased lactate production. Together, these findings indicate that BCG induces systemic and CNS myeloid cell reprogramming that limits neuroinflammation, enhances tau clearance, and rescues cognitive and neurodegenerative phenotypes in a tauopathy model. BCG is a safe, readily available therapy that merits consideration as a preventive agent against dementia. One sentence summaryBCG therapy prevents tauopathy in PS19 mouse model.

The choroid plexus epithelial cells (CPECs) at the blood-cerebrospinal fluid (CSF) interface possess an exceptionally high mitochondrial content to support CNS homeostasis. Oncocytic CPECs (O-CPECs), characterized by enlarged and granular eosinophilic cytoplasm composed of excessive abnormal mitochondria, likely contribute to an energetic failure of this energy-demanding tissue. The relationship between O-CPECs and other CPEC pathologies in humans, such as Biondi body (BB) amyloid inclusions, remains poorly defined. In the present study, using H&E-stained sections from 68 postmortem cases, we classified O-CPECs by quantitative size criteria and cytological features, and found an increase in the prevalence of O-CPECs with age after adjusting for sex and tissue source. After excluding two influential control cases, there was evidence for a further increase associated with Alzheimers disease. Using antibodies to ATP synthase beta chain to classify O-CPECs, and thioflavin-S to identify BBs, we revealed an increased prevalence of BBs in O-CPECs compared to neighboring non-oncocytic cells. Small multiple BB inclusions were responsible for the increase in O-CPECs, while the prevalence of larger inclusions was decreased in O-CPECs. Together, our data support a clear age-associated oncocytic transformation of CPECs and implicate mitochondrial dysfunction-amyloid interactions.

Astrocytes are key regulators of lipid metabolism, and dysregulated astrocytic lipid processing is implicated in Parkinsons disease (PD) pathogenesis. Our prior genome-wide screens identified ACSBG1, an astrocyte-enriched acyl-CoA synthetase, as a candidate regulator of -synuclein (-Syn) levels. However, how ACSBG1 links lipid reprogramming to inflammatory astrocyte activation and -Syn pathology remains unknown. We compared the transcriptomic, cytokine, and lipid secretomes of TNF- and IL-1 stimulated primary astrocytes from wild-type (WT) and Acsbg1 knockout (KO) mice. In vivo, we crossed Acsbg1 KO mice with a Thy1--Syn PD model to assess behavior, neuroinflammation, synaptic integrity, and -Syn levels. Following cytokine exposure, Acsbg1 KO astrocytes mounted an attenuated inflammatory transcriptional response, secreting significantly fewer inflammatory mediators (e.g., IL-6, RANTES, MIP-3) and less long-chain Sphingosine 20:1 than WT astrocytes. Importantly, exogenous Sphingosine 20:1 or cytokines from WT reactive astrocytes induced neuronal -Syn phosphorylation (pS129). In vivo, Acsbg1 deletion in Thy1--Syn mice reduced astrogliosis, rescued synaptic and behavioral deficits, and decreased total and pS129--Syn. These findings establish ACSBG1 as a key regulator of inflammatory astrocyte signaling that contributes to -Syn phosphorylation via specific cytokine and lipid mediators, identifying ACSBG1 as a novel therapeutic target for modulating astrocyte-neuron communication in PD.

Malignant pleural mesothelioma (MPM) is a rare malignancy characterised by extensive structural genomic alterations and a low burden of recurrent single nucleotide variants. However, the full spectrum and functional impact of structural variation (SVs) remain incompletely understood because short-read sequencing has limitation ability to resolve complex genomic rearrangements. Here, we performed integrated short-read and long-read whole-genome sequencing on tumour-normal pairs from three MPM patients, together with RNA sequencing and nanopore-derived promoter methylation profiling. Long-reads sequencing substantially improved SV detection, identifying 61-156 novel SVs per sample, including complex rearrangements and breakpoint-resolved events affecting cancer-associated genes. Complex SV clusters consistent with chromoplexy and chromothripsis were observed and frequently involved oncogenes. Integration with transcriptomics data showed that several SVs-affected genes, including WEE1 and GPC6, exhibited increased expression independent of gene dosage. Promoter methylation analysis revealed a conserved bimodal methylation landscape across tumours and a significant inverse relationship with gene expression. SV-associated genes showed coordinated promoter hypermethylation and transcriptional activation, suggesting that SVs may influence gene regulation through epigenetic mechanisms. Survival analysis using the TCGA-MESO cohort further showed that elevated expression of WEE1 and GPC6 was associated with poorer overall survival. Together, these findings highlight the value of long-read sequencing for uncovering functionally and clinically relevant structural variation in MPM.

Presenilin 2 (PS2) mutations cause familial Alzheimers disease, yet their effects beyond amyloid processing remain poorly understood. Here, we investigated how PS2 deletion and the N141I mutation affect neuronal lipid homeostasis and mitochondrial dynamics in mouse primary neurons. Both PS2 deletion and N141I mutation reduced neuronal lipid content. However, exogenous lipid supplementation rescued this deficit only in N141I-expressing neurons, indicating a partial loss-of-function effect. N141I neurons also displayed reduced OPA1, a mitochondrial fusion regulator, restored by lipid supplementation. RNA-sequencing identified Gbf1, a Golgi-specific guanine nucleotide exchange factor, as selectively downregulated in N141I but not knockout tissue, which was confirmed at the protein level in mouse brain and primary neurons. Gbf1 knockdown in mouse embryonic fibroblasts (MEFs) recapitulated the N141I lipid profile. Together, these findings reveal a PS2-GBF1-lipid-mitochondria axis disrupted specifically by the N141I mutation, suggesting an amyloid-independent pathway contributing to neurodegeneration and identifying potential therapeutic targets for familial Alzheimers disease.

Guillain-Barre syndrome is an acute immune-mediated polyradiculoneuropathy with heterogeneous outcomes and limited molecular biomarkers for diagnosis, disease monitoring, and prognosis. To elucidate the circulating proteomic profile of this disorder and identify candidate biomarkers associated with disease activity and recovery, we measured over 6,500 proteins using an aptamer-based proteomic platform. We analysed paired, longitudinal sera from 20 patients at disease onset and one-year follow-up, alongside 15 healthy controls. Unbiased differential protein abundance and gene-set enrichment analyses were performed. Candidate proteins were validated using conventional immunoassays in a cohort including healthy and disease controls. We identified 39 differentially abundant proteins between the acute and recovery phases and 248 proteins altered in acute Guillain-Barre syndrome compared to controls. The acute phase was characterised by a marked enrichment in systemic immune cascades and muscle sarcomere proteins, alongside a significant depletion of axonal adhesion molecules. Serum amyloid A1 (SAA1) emerged as the most strongly increased protein in the acute phase. Validation through independent immunoassays confirmed robust serum amyloid A elevations at disease onset relative to the one-year recovery phase, healthy controls, and relevant post-infectious and neuromuscular disease controls (acute disseminated encephalomyelitis and myasthenia gravis), underscoring a peripheral nerve-specific inflammatory response. Furthermore, unexpected elevations of cardiac troponin T (cTnT) were observed at disease onset. Clinical validation using high-sensitivity assays demonstrated that cTnT exceeded the diagnostic 99th percentile upper reference limit in 25.5% of acute Guillain-Barre syndrome patients. A similarly high frequency of elevation in the myasthenia gravis disease control group (42.1%) suggests these increases predominantly reflect neuromuscular damage rather than myocardial injury. Finally, Mendelian randomisation provided causal genetic evidence linking specific systemic proteins to disease susceptibility, identifying robust roles for SERPING1 (plasma protease C1 inhibitor), CNDP1 (an antioxidant protein), and CRISPLD2 (a lipopolysaccharide-binding protein that regulates endotoxin function). Together, this comprehensive proteomic characterisation reveals distinct, stage-specific molecular signatures in Guillain-Barre syndrome. Importantly, it suggests SAA1 as a robust marker of acute peripheral nerve inflammation and challenges the conventional interpretation of elevated cTnT in severe neuropathies and neuromuscular disorders. Furthermore, this work provides a novel dataset to explore future targeted therapeutic development in Guillain-Barre syndrome.

Post-translational modifications critically regulate neurodegenerative disease progression. In Alzheimers disease (AD) and tauopathies, Tau hyperphosphorylation promotes aggregation and pathological spreading, whereas O-GlcNAcylation has emerged as a protective modification alongside its interplay with phosphorylation. However, the role of in vitro site-specific and global O-GlcNAcylation in Tau proteinopathy remains elusive. Here, using full-length Tau-441 (2N4R), we showed that O-GlcNAcylated Tau aggregated slowly, formed distinct aggregate morphology and exhibited reduced seeding capacity compared to wild-type (WT) Tau. Under phase-separated conditions, O-GlcNAcylated Tau formed oligomer like condensates. Mutation of the key O-GlcNAc sites reduced O-GlcNAc-transferase (OGT) mediated O-GlcNAcylation, cellular transmission and affected cross-talk with phosphorylation relative to WT. OGT overexpression alleviated WT-Tau toxicity in cells, and O-Tau fibrils were less toxic to primary cortical neurons compared to WT Tau fibrils. Finally, an in-house novel site-specific S422 O-GlcNAc-Tau antibody revealed reduced S422 O-GlcNAcylation in AD brain tissues, highlighting its protective role in AD pathogenesis.

Parkinsons disease (PD) is a neurodegenerative disorder characterized by a prolonged prodromal stage that culminates in motor deficits. Current PD therapies primarily alleviate symptoms, underscoring the need for disease-modifying strategies. Glucagon-like peptide-1 (GLP-1) analogs showed early promise as candidate disease modifiers, but recent clinical results have been inconsistent, and their mechanism of action remains poorly defined. Here, we employed our SncaG51D/G51D knock-in mouse model to investigate the effects of subcutaneously administered GLP-1 analogs, semaglutide and lixisenatide. Both analogs reversed motor and non-motor deficits and reduced gliosis and detergent-insoluble -synuclein. Bulk and single-nuclei transcriptomics together with CellChat-based intercellular communication analysis revealed that GLP-1 analogs normalize early striatal mitochondrial and inflammatory dysregulation and restore neuregulin (NRG) and neurexin (NRXN) signaling networks to wild-type levels. Treatment was effective when initiated either before or shortly after symptom onset, defining an early therapeutic window for GLP-1 analog therapy in PD.

Pathogenic variants in ATP13A2, which encodes an endolysosomal polyamine exporter, cause Kufor-Rakeb syndrome and are associated with early-onset parkinsonism and related neurodegenerative disorders, however, the mechanisms by which ATP13A2 dysfunction drives disease remain incompletely defined. In Atp13a2 knockout mice, we identified an early, transient reduction in brain polyamines that precedes overt gliosis and behavioural abnormalities. Pharmacological polyamine depletion exacerbates phenotypes, whereas oral supplementation of spermidine, but not spermine, rescues parkinsonian symptoms establishing metabolic polyamine deficiency as a pathogenic driver. Mechanistically, spermidine counteracts microglia lysosomal dysfunction in the brain and exerts mitochondrial antioxidant and anti-inflammatory effects in primary mouse microglia, thereby improving neuronal integrity. In the absence of Atp13a2, microglial spermidine import relies on the related polyamine transporter Atp13a3. Importantly, these findings translate to human systems, whereby spermidine attenuates inflammation in ATP13A2-deficient human differentiated microglia, while postmortem ATP13A2-deficient brain analysis confirms increased microglia reactivity. Spermidine also rescues motor deficits and dopaminergic neuron loss in ATP13A2-deficient Drosophila and other fly parkinsonism models. Together, these findings identify early polyamine dysregulation as a mechanistic contributor to ATP13A2-associated parkinsonism and nominate spermidine supplementation as a potential therapeutic strategy for ATP13A2-driven pathology and possibly a broader range of parkinsonian sub-types.

Synapse loss is an early feature of neurodegeneration and may provide sensitive biomarkers for experimental medicine. Positron emission tomography (PET) with the synaptic vesicle glycoprotein 2A radioligand [11C]UCB-J shows widespread signal reduction across dementias. However, it remains unclear which aspects of synaptic integrity [11C]UCB-J PET measures. We developed a histological-imaging pipeline to quantify structurally intact synapses in post-mortem brain tissue. We applied it to six donors with the tauopathy progressive supranuclear palsy (PSP) who had ante-mortem [11C]UCB-J-PET, alongside six controls across 11 brain regions. Synapse loss in PSP was widespread but region-specific across cortical, subcortical, and brainstem regions. Greater synapse loss was associated with higher tau burden and pathology, and cortical synaptic density correlated with ante-mortem cognition. Post-mortem synaptic density correlated with in vivo [11C]UCB-J-PET signal. This study provides validation of SV2A PET as a biomarker of synaptic density and supports integration of imaging with histopathology in neurodegenerative disease research.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease of poor prognosis, for which age is the strongest risk factor. Despite significant progress in the discovery of ALS-associated mutations, no model explains how such a diversity of mutations converges in a common pathology. In addition, most ALS cases are sporadic and lack known genetic drivers. We recently reported that arginine-rich peptides arising from the C9ORF72 mutation trigger a widespread accumulation of orphan ribosomal proteins (oRP). Here, we show that oRP accumulation is also observed upon expression of other RNA-related ALS mutations, such as hnRNPA2D290V and TDP-43A315T, as well as upon exposure to the ALS-related neurotoxin {beta}-N-methylamino-L-alanine (BMAA). Furthermore, the transcriptional signature of patients with sporadic ALS resembles that of Diamond-Blackfan anemia (DBA), a known ribosomopathy. Supporting the usefulness of our in vitro data, a transcriptional signature defined from these models provides diagnostic and prognostic value in ALS patients. We propose that the accumulation of oRPs due to dysfunctional ribosome biogenesis is a molecular hallmark of ALS that can contribute to the progressive loss of motor neurons in the disease.

Extracellular vesicles (EVs) hold promise as minimally invasive biomarkers for neurodegenerative proteinopathies, but disease- and stage-specific profiles remain unclear. For this study, we enrolled 378 participants across five centers and the MJFF-BioFIND cohort: 100 healthy controls [HC], 64 isolated REM sleep behavior disorder [iRBD], 41 DeNovo Parkinsons Disease [PD], 89 Late PD, 32 other Synucleinopathies, and 52 Tauopathies. All participants underwent clinical evaluation and blood collection. The 77 subjects from the BioFIND cohort also provided CSF samples. EV concentration and size were assessed by nanoparticle tracking analysis; flow cytometry quantified tetraspanins (CD9/CD63/CD81) and 37 surface markers. Multivariable logistic regression, receiver operating characteristic analyses (ROC), and repeated random forest (rRF) classifiers evaluated diagnostic utility. Late PD showed the highest EV concentrations compared to HC and other disease groups. Participants exhibited distinct EV surface immunophenotypes, with the iRBD group displaying the most extensive immune activation signature vs HC, followed by PD patients. Multivariate logistic regression analysis identified diagnostic marker panels: CD3/CD9/CD25/CD56 for iRBD, SSEA4 for Late PD, CD146/CD209 for Synucleinopathies, and CD8/CD45/CD62P for Tauopathies. ROC confirmed good discriminatory performance, with CD56 emerging as the strongest single predictor for iRBD vs HC, SSEA4 showing high sensitivity for Late PD, and marker combinations providing optimal balance for Synucleinopathy/Tauopathy classification vs HC. In the CSF BioFIND subset, Late PD EVs exhibited increased myeloid (CD1c), adhesion (CD29), activation (CD69), and epithelial (CD326) markers compared to HC. Among these, CD326 was independently associated with Late PD diagnosis. Machine learning classifiers using all 37 surface antigens achieved excellent training performance (91.7-94.3% accuracy for iRBD/Synucleinopathies vs HC) and maintained robust validation accuracy, particularly for iRBD (77.8%) and DeNovo PD (76.6%) vs HC. EV immuno-phenotyping reveals distinct signatures across the neurodegenerative proteinopathies spectrum, with the highest diagnostic utility for prodromal iRBD detection. Longitudinal validation and cell-of-origin refinement represent key next steps toward clinical translation.

Oligodendroglioma is a primary central nervous system tumor classified by the presence of isocitrate dehydrogenase (IDH) mutations and codeletion of 1p/19q. Here we describe the generation of an IDH-mutant 1p/19q-codeleted oligodendroglioma mouse model using in utero electroporation. We identified IDH1R132H, PIK3CAE545K, CicKO, Fubp1KO and Cdkn2aKO as the optimal combination (termed OligoCdkn2a) to drive fully penetrant tumors that histologically resemble human grade II/III IDH-mutant, 1p/19q-codeleted oligodendroglioma. Replacing Cdkn2a with Trp53 loss in this mouse model shifted tumor histology towards high grade astrocytoma. OligoCdkn2a tumors displayed metabolic and transcriptional changes associated with IDH and CIC mutations, and single cell sequencing identified a bias towards oligodendrocyte differentiation compared to an IDH wild-type glioblastoma mouse model. OligoCdkn2a tumors represent the first mouse model system to recapitulate the genetic, histological and transcriptional features of human IDH-mutant 1p/19q-codeleted oligodendrogliomas, offering a platform to further dissect tumor biology and test new therapeutic strategies.

To resolve discrepancies in the literature regarding the association between Alzheimers disease (AD) and Biondi body (BB) amyloid in choroid plexus epithelial cells (CPECs), we investigated postmortem hippocampal paraffin blocks with and without a neuropathological diagnosis of AD (n=26-27 each). Similar to previous studies, age was associated with an increased fraction of hippocampal-associated CPECs bearing thioflavin S-positive BBs (p=0.004). In addition, we found that paraffin block storage time was associated with decreased BB detectability (p=0.038) while sex had no effect (p=0.577). Controlling for age, sex, and storage time, AD was associated with a near-significant increase in the BB-containing CPEC fraction (p=0.066) and a significantly greater load of BB-like amyloid in hippocampal-associated ependymal cells (p=0.032). The AD-BB association contrasts with our findings on choroid plexus from the atrium of the lateral ventricle, which lacked this association. We discuss potential explanations for the apparent discrepancy such as regional amyloid cross-seeding.

Alzheimers disease (AD), the leading cause of dementia, is characterized by early synaptic dysfunction that precedes overt cognitive decline. While amyloid-{beta} and Tau remain central to AD pathogenesis, molecular triggers of synapse weakening remain unclear. Here, we investigated AETA, a novel brain-secreted peptide derived from amyloid precursor protein (APP), as a potential mediator of synapse dysfunction in AD. We previously identified AETA as a unique modulator of NMDA receptor activity in the healthy brain; however, its role in AD etiology was yet to be explored. Post-mortem analyses of human hippocampal and prefrontal cortex tissues revealed significantly elevated AETA levels in AD patients, particularly in females. To further explore the contribution of AETA to AD synaptic pathology, we analyzed a new mouse model, the AETA-m mouse, exhibiting chronically increased brain AETA expression. Hippocampi of female AETA-m mice display an increase in the number of astrocyte and microglia, but no overt neuroinflammation. RNA sequencing of female AETA-m hippocampi revealed alterations in synaptic gene expression that closely paralleled those observed in vulnerable human AD brain regions, most notably in the hippocampus. These two phenotypes were absent in males. Functionally, hippocampal neurons from AETA-m mice displayed impaired NMDA receptor signaling, dendritic spine loss, and memory deficits especially in females, mirroring early AD-associated synaptic dysfunction. Together, these findings identify AETA as a novel key contributor of synaptic vulnerability in AD and associated memory processing, especially in females. Targeting AETA signaling may therefore offer new therapeutic avenues for preventing or mitigating synaptic and cognitive decline in AD.

Efficient cerebrovasculature is vital to neuronal health and cognition and evidence shows most dementia patients have cerebrovascular abnormalities. Brain vasculature is regulated by Vascular Endothelial Growth Factors (VEGFs) binding VEGF receptor2 (VEGFR2) and stimulating angiogenesis, and neuroprotection. Presenilin1 (PS1) is the main proteolytic component of {gamma}-secretase and PS1 mutants are the most common cause of Familial Alzheimer Disease (FAD). Here we show that an ADAM17 cleavage of extracellular VEGFR2 produces the membrane-bound {gamma}-secretase substrate VEGFR2/CTF1 (called VCTF1), comprising the transmembrane and intracellular domains of VEGFR2. PS1 FAD mutants and {gamma}-secretase inhibitors both accumulate VCTF1 and suppress VEGF-A-induced brain angiogenesis. Moreover, PS1 FAD mutants, {gamma}-secretase inhibitors, and PS1 downregulation, all decrease {gamma} secretase processing of VCTF1, thereby increasing its accumulation and impairing VEGF-A-induced VEGFR2 dimerization/activation, signaling, and endothelial cell (EC) functions. Importantly, VCTF1 binds fulllength VEGFR2 monomers suppressing VEGFR2 dimerization/activation, signaling, and EC functions. These data show that VCTF1 suppresses VEGFR2 dimerization and downstream signaling and functions of the brain VEGF-A-/VEGFR2 system. PS1 FAD mutants increase vulnerability of brain neurons to ischemic stress and exert antimorphic effects on {gamma}-secretase cleavage of VCTF1, increasing its concentration and abolishing VEGF-A-induced VEGFR2 dimerization/activation, signaling, neuroprotection and cognition. Importantly, we detected molecular markers of decreased VEGFR2 dimerization and angiogenic dysfunction in human brain tissue from PS1 FAD mutant genotypes. Together, our data suggest a pathway through which FAD mutants promote dementia by increasing VCTF1 and decreasing brain angiogenesis and neuroprotection, suggesting that PS1 FAD patients may benefit from therapeutic methods that decrease brain VCTF1.

BackgroundAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motor neuron (MN) loss, muscle atrophy and paralysis. Although traditionally considered a MN-specific disease, accumulating evidence supports a crucial contribution of skeletal muscle pathology to disease onset and progression. Except for specific mutations, to date there is no effective treatment for ALS. FOXO transcription factors regulate programs of atrophy, metabolism and stress response in skeletal muscle, and their inhibition has shown beneficial effects in cellular and Drosophila models of ALS. MethodsIn this study, we investigated whether pharmacological FOXO inhibition (iFOXO) could modify disease progression and muscle pathology in female hSOD1G93A mice. Mice received daily oral administration of iFOXO starting at presymptomatic (P50; n=5 per group) or symptomatic (P90; n=9 mice per group) stages until end-stage. Body weight was monitored longitudinally, and motor performance was evaluated using grip strength and hanging-wire tests. Tibialis anterior and soleus muscles, representing fast- and slow-twitch muscles respectively, were analyzed by histology and immunofluorescence to assess fiber atrophy, fibrosis, lipid accumulation, satellite cell pool and fiber type composition. Quadriceps muscles (n=3 per group) were used for RNA-seq analysis. ResultsWhile histological analyses revealed severe fiber atrophy and increased fibrosis in hSOD1G93A mice, satellite cell numbers were preserved or mildly increased in a muscle and treatment onset dependent manner. iFOXO treatment did not improve motor performance, survival or attenuate muscle atrophy. Transcriptomic profiling indicated that genotype was the predominant driver of gene expression changes, while iFOXO produced only subtle, treatment onset dependent effects on pathways related to oxidative stress responses, mitochondrial function and adaptive metabolism. ConclusionOverall, FOXO inhibition alone showed limited therapeutic benefit in the hSOD1G93A ALS mouse model. These findings highlight the dominant influence of ALS driven molecular alterations over pharmacological modulation and emphasize the need for combinatorial therapeutic strategies targeting multiple disease mechanisms, including those preserving nerve health.