Brain

Objectives: Seizure freedom follows surgery in 67% of children with drug-resistant epilepsy, but imaging biomarkers could improve patient selection, epileptogenic zone localisation, and outcome prediction. We assessed whether diffusion MRI abnormalities predicted seizure freedom when resected; aligned with stereo-EEG seizure-onset and interictal zones; distinguished patients with/without an identified onset zone; and localised the epileptogenic zone in MRI-negative cases. Methods: We retrospectively studied children undergoing focal resection (n=110) or stereo-EEG (n=61) between 2015-2023, alongside healthy controls aged 6-18 (n=69), using identical 3T MRI diffusion protocols. Age- and sex-adjusted normative models generated mean diffusivity (MD) and fractional anisotropy (FA) voxelwise z-score maps to identify dominant abnormalities. In resection patients, abnormality-resection overlap was related to 12-month or longer Engel outcome. In stereo-EEG patients, z-scores were compared across seizure-onset, interictal, and uninvolved grey-matter contacts. In lesion-negative patients, abnormalities were compared with PET hypometabolism and stereo-EEG findings. Results: Greater resection of MD abnormalities predicted seizure freedom, especially with overlap >0 (mean differences 17%, 23%; Pperm=0.0086, <0.001), and higher odds of Engel I (OR 1.31/10%; AUC 0.723; Youden threshold 36%). FA showed similar associations. Seizure-onset contacts had higher MD and lower FA z-scores than uninvolved grey matter (+0.65, 0.18; Pperm<0.001, =0.001), with interictal contacts intermediate. Abnormalities were more widespread and contralateral in patients without an identified onset zone. In lesion-negative patients, abnormalities co-localised with PET (20/28 fully, 6/28 partially) and stereo-EEG (17/24 fully, 3/24 partially). Interpretation: Diffusion MRI abnormalities aligned with invasive electrophysiology, predicted seizure freedom when resected, and co-localized with PET/stereo-EEG, supporting an important role in presurgical evaluation.

Gaucher disease is a rare lysosomal storage disorder caused by autosomal recessive mutations in the GBA1 gene, encoding the lysosomal enzyme glucocerebrosidase. Gaucher disease is classified in 3 different subtypes depending on the presence and severity of neurological involvement, with type 2 resulting in fatal early-onset neuropathology and patients exhibiting developmental delays, seizures and early death. Studies investigating disease mechanisms of neuronopathic Gaucher disease are mainly based on animal models and focus predominantly on late neuronal phenotypes. Here, we established healthy control and Gaucher disease patient-derived iPSC lines and engineered them to obtain isogenic control and disease lines. Using these lines, we generated cortical and subpallial brain organoids in which we identified early-onset lipid dysregulation in form of glucosylceramide accumulation, highly elevated glucosylsphingosine, and a later increase in ganglioside levels, recapitulating clinical findings. Furthermore, single-cell transcriptomic profiling uncovered novel phenotypes in both cortical and subpallial forebrain organoids. Subpallial alterations consisted of an early increase in migrating interneurons in subpallial organoids, which upregulated cholesterol metabolism. Cortical alterations showed early upregulation of mitochondrial genes and a downregulation of proliferation, with a subsequent switch from GABAergic to glutamatergic neuron fate with a striking increase in gene expression related to the synaptic assembly. Functional assays demonstrated a marked hyperexcitability of cortical organoids and reduced response to GABA-A receptor blockage in Gaucher disease. Additional 2D neuronal network models confirmed the organoid data and showed that both glutamatergic and GABAergic neurons contribute to the phenotype, with hyperexcitability of Gaucher glutamatergic neurons and incapacity of Gaucher GABAergic neurons to balance the excessive excitation. This alteration represents a clinically significant phenotype as many patients exhibit an excitation/inhibition imbalance leading to treatment-resistant seizures, hastening their decline. In conclusion, our defined human models of Gaucher disease identify novel and clear phenotypes that can be used for drug screening or aid in development of new therapeutic strategies to ameliorate Gaucher disease.

Selective vulnerability is a hallmark of Parkinson's disease (PD): post-mortem, dopamine-containing cell loss in the substantia nigra first and most severely affects calbindin-poor compartments termed nigrosomes. Testing this in vivo has been limited by circularity, as MRI studies have delineated nigrosomes from the same disease-related contrast they then measure. Here, we warp histology-derived, calbindin-validated probabilistic masks of nigrosomes 1-5 into a cohort-specific multimodal 7 Tesla quantitative MRI template, providing a degeneration-independent anatomical scaffold, in 28 patients with PD and 28 age- and sex-matched controls. In controls, nigrosomes differ from the surrounding nigral matrix in magnetic susceptibility and R1. PD shifts nigrosomal values upward relative to the matrix in susceptibility, R2*, and R1, concentrated in nigrosomes 1, 2, and 4, whereas whole-nigra analysis shows no group difference. Within the matrix, disease effects are largest caudally and emerge dorsally from the ventral tier, and susceptibility alterations in nigrosomes 1 and 4 track contralateral motor symptoms asymmetry. The multimodal pattern suggests that the detectable signal reflects predominantly secondary, iron-associated glial processes rather than neuronal loss itself. These findings recover the post-mortem spatial pattern of nigral vulnerability in vivo and establish a degeneration-independent framework for subregional nigral imaging in PD.

Parkinson's disease is asymmetric, but representations that collapse left--right measurements discard that direction. We separated overall dopamine-transporter availability from hemispheric distribution: mean putamen specific-binding ratio (SBR) indexed overall DaT signal, whereas signed asymmetry retained which hemisphere was relatively more affected. Signed asymmetry aligned with contralateral MDS-UPDRS Part III laterality in PPMI (n=1,367; r=0.676) and S4 (n=56; r=0.551). In 1,204 PPMI landmarks, each 0.1 asymmetry corresponded to a 0.0507 increase in 12-month laterality (95\% CI 0.0387--0.0626); held-out \(R^2\) improved 0.0176 over non-directional imaging but was uncertain under a bounded link. Exploratory imaging--clinical disagreement marked lower side persistence (OR=0.491 per IQR-standardized unit; 0.297--0.711). Signed direction therefore distinguishes mirror-image and conflicting dopaminergic--motor states erased by mean-only summaries. This is a reproducible biological coordinate, not global progression, treatment benefit or clinical utility.

Isolated focal dystonia is a rare movement disorder characterized by abnormalities in brain structure and function. The genes underlying isolated focal dystonia are not fully elucidated, and genetic studies are constrained by incomplete penetrance and small family sizes. Neuroimaging endophenotypes shared by patients and unaffected relatives can reveal genetic liability independently of clinical manifestation and offer a strategy for advancing gene discovery. We developed DystoniaGeneNet, a 3D convolutional neural network that predicts familial status from T1-weighted brain MRIs. We then used its predictions to guide genetic analyses in isolated focal dystonia. DystoniaGeneNet was trained on 40 patients with familial laryngeal dystonia and 40 healthy controls, then applied to independent cohorts of 21 patients with familial isolated focal dystonia, 364 patients with sporadic dystonia, and 98 unaffected relatives. Model predictions were incorporated into variant prioritization and segregation analysis in 214 individuals with whole-exome sequencing data, and results were replicated in another 738 independent exomes, in genetic data from a hospital-based biobank (892 dystonia cases, 2,475 controls), and in the All of Us Research Program genetic data (1,343 dystonia cases, 6,840 controls). DystoniaGeneNet discriminated familial dystonia from healthy controls in the training set and correctly classified 85.7% of independent familial cases, using a biomarker centred on the corpus callosum and inferior temporal gyrus. Across the discovery and replication cohorts, we identified rare, likely pathogenic genetic variants in RAP1GAP and TNN segregating with disease in families. Additional variants were found in singletons with isolated focal dystonia. In patients with clinically sporadic dystonia but predicted to have familial features, we observed multiple rare variants in ITSN2, including three high-confidence loss-of-function variants, and an enrichment of damaging missense variants in its Dbl homology domain. To determine the functional impact of discovered genetic variants, we assessed gene expression and splicing via qPCR and RNA sequencing (n = 74), revealing reduced RAP1GAP and ITSN2 expression in variant carriers. At the pathway level, rare nonsynonymous variants in brain-expressed matrisome genes were associated with dystonia (P = 0.012). Our strategy utilizing a deep learning-derived neuroimaging endophenotype to empower gene discovery uncovered RAP1GAP, TNN, and ITSN2 as novel genes associated with isolated focal dystonia. These genes converge on perisynaptic extracellular matrix-synapse signalling, implicating a mechanism linked to synaptic plasticity deficits, and identifying a molecular substrate for network-level brain abnormalities that characterize this disorder. Further, we exemplify a generalizable framework for leveraging endophenotypes in rare neurogenetic diseases with incomplete penetrance.

Temporal lobe epilepsy (TLE) is associated with altered functional connectivity, yet its effects on connector hubs, regions supporting long-range and inter-network communication, remain poorly understood. We used SParsity-based Analysis of Reliable k-hubness to characterize connector hub reorganization in unilateral TLE compared with healthy controls. Patients exhibited significant widespread reductions in k-hubness involving the occipital, cingulate, and precuneus regions, ipsilateral hippocampus, and the bilateral pallidum. Compared to the distribution of k-hubness in healthy controls, the hub disruption index revealed rapid loss of k-hubness alongside emergence of new hubs in contralateral homologous regions. To investigate microstructural substrates of these functional changes, apparent diffusion coefficient and fractional anisotropy from diffusion magnetic resonance imaging were examined. The strongest associations with k-hubness were observed in subcortical structures and the hippocampus. These findings demonstrate that TLE is characterized by widespread, asymmetric connector hub reorganization extending beyond the epileptogenic temporal lobe, revealing distinct patterns of network disruption and reorganization across the brain.

Pathogenic variants in O-GlcNAc transferase, which catalyses nucleocytoplasmic protein O-GlcNAcylation, cause a neurodevelopmental disorder (OGT-NDD) characterised by intellectual disability and motor impairments. However, mechanisms linking O-GlcNAc dyshomeostasis to brain development remain unclear. Longitudinal neuroimaging of an individual carrying the p.Asn648Tyr OGT-NDD variant, combined with developmental and molecular analyses of an OgtN648Y/y mouse model, revealed that the mouse phenocopied the impaired cerebellar growth in the patient. Altered OGT distribution and reduced Calbindin expression preceded reduced Purkinje and granule cell densities and molecular layer thinning, alongside increased microglial density, persistent phagocytic cup-like structures, and reduced interleukin (IL)-4 levels. Pharmacological OGT inhibition reduced IL-4-induced reporter activity in vitro, while primary OgtN648Y/y microglia exhibited blunted IL-4- induced O-GlcNAcylation with enrichment of inflammatory and innate immunity programmes. These findings link impaired OGT catalytic function to postnatal cerebellar maturation during a critical developmental window and identify IL-4-associated microglial responses as a contributor to cerebellar pathology in OGT-NDD.

Accurate localization of the seizure onset zone (SOZ) is essential for planning resection or ablation in patients with focal drug-resistant epilepsy (DRE). However, the true SOZ cannot be directly observed during clinical evaluation, so precise electrode-level annotations are rarely available. To address this limitation, we developed a weakly supervised multiple-instance learning (MIL) framework in which labels were constructed from electrode resection status and postsurgical outcome. A shared gated recurrent unit (GRU) with temporal attention encoded each electrode's peri-onset neural fragility sequence. And attention-based pooling integrated information across variable numbers of electrodes to estimate whether each electrode group contained SOZ-related evidence. The cohort comprised 42 patients with DRE from three datasets, including 29 with successful and 13 with failed postsurgical outcomes. These patients contributed 136 seizure epochs. The cohort was divided at the patient level into training, validation and held-out test sets containing 25, 8 and 9 patients, respectively, with all data from each patient retained in the same subset. Predictions from non-resected regions were evaluated at the seizure-epoch and patient levels to assess postsurgical outcome discrimination for individual seizures and after aggregation across seizures from the same patient, respectively. At the seizure-epoch level, the proposed framework achieved an area under the receiver operating characteristic (ROC) curve (AUC) of 0.828, with a 95% confidence interval (CI) of 0.511-1.000, and performed comparably to Manifold Oblique Random Forests (MORF). At the patient level, the framework achieved an AUC of 0.944, with a 95% CI of 0.677-1.000, and yielded a numerically higher AUC than MORF. However, DeLong's test did not show a statistically significant difference between the methods, with a P value of 0.398. These findings support the feasibility of extracting clinically meaningful SOZ-related information from electrode-wise neural fragility sequences without precise electrode-level labels. Because the held-out test set included only nine patients and the CIs were wide, these preliminary findings require validation in larger independent cohorts.

Absence epilepsy is a generalized non-convulsive epilepsy characterized by recurrent absence seizures (ASs) and enhanced GABAA receptor-mediated tonic inhibition of thalamocortical (TC) neurons has been shown to lead to ASs. Serotonergic signalling is an important modulator of these seizures, yet the contribution of specific 5-HT receptor subtypes remains incompletely understood. Here, we investigated whether endogenous serotonergic signalling through 5-HT2A receptors (5-HT2ARs) contributes to pathological tonic inhibition and ASs expression. Patch-clamp recordings were obtained from ventrobasal (VB) TC neurons of Genetic Absence Epilepsy Rats from Strasbourg (GAERS) and non-epileptic control (NEC) rats. The selective 5-HT2AR antagonist MDL11,939 had no effect on tonic GABA-A currents in NEC TC neurons but significantly reduced the enhanced tonic current in GAERS neurons, revealing a disease-dependent contribution of endogenous 5-HT2AR signalling. MDL11,939 administered bilaterally into the VB of freely moving GAERS by reverse microdialysis did not alter ASs. This dissociation between the modulation of a disease-associated cellular mechanism and seizure outcome suggests that the previously reported reduction of ASs by systemic 5-HT2AR blockade may involve mechanisms outside the VB.

Parkinsons disease is a neurodegenerative disorder characterized by altered subcortical-cortical connectivity, leading to motor and cognitive deficits. Saccadic eye movement abnormalities are among the earliest and most persistent markers of the disease, serving as sensitive indicators of disrupted oculomotor and cognitive control. While changes in average saccadic behavioral measures are widely reported in Parkinson's disease, intra-individual variability in saccadic performance and the underlying network dysfunction remain poorly understood. Here, we quantified intra-individual saccadic variability in early-stage Parkinsons disease and identified its functional correlates within the resting-state saccadic network. We analyzed data from 91 patients with early-stage Parkinsons disease and 46 healthy controls who underwent oculomotor testing and resting-state functional magnetic resonance imaging. First, at the behavioral level, we assessed intra-individual variability in saccadic performance within each group using the coefficient of variation of reaction time and normalized peak velocity across trials. Second, at the brain level, we assessed group differences in static and dynamic functional connectivity across 39 regions comprising the saccadic network. We examined the relationship between network connectivity and saccadic variability using partial least squares analysis. We also quantified network organization using graph-theory measures of global efficiency and clustering coefficient. Finally, we tested the relevance of intra-individual saccadic variability and network features in distinguishing patients from healthy controls using a multivariate Mahalanobis classifier. Our results showed that, compared to HC, patients had higher intra-individual variability in saccadic behavioral measures of reaction time (pHolm = 0.012) and normalized peak velocity (pHolm = 0.012). Interestingly, patients had (i) reduced static and dynamic connectivity within the saccadic network and (ii) weaker associations between network connectivity and intra-individual saccadic variability of specifically normalized peak velocity. These results were particularly driven by regions within the cognitive saccade network. The classifier that integrated intra-individual saccadic variability and network connectivity achieved 95.62% accuracy in distinguishing patients from healthy controls, with dynamic connectivity contributing more strongly to classification performance than static connectivity. We demonstrate that elevated intra-individual variability of saccades, underpinned by altered functional connectivity within cognitive-oculomotor networks, is a prominent feature of early-stage Parkinsons disease. Emerging as a promising physiological marker of disease pathophysiology, intra-individual variability offers a powerful new framework to refine early diagnosis and improve the tracking of neurodegeneration before severe clinical milestones are reached.

Friedreich ataxia (FRDA) is an inherited multisystem disorder caused by a GAA repeat expansion in the FXN gene and consequent frataxin deficiency, causing progressive neurodegeneration and heart disease. Clinical studies have documented autonomic dysfunction in FRDA, including elevated resting heart rate, raised plasma catecholamines and a high burden of urinary, bowel and sexual symptoms. Consistent with this, autopsy studies show degeneration of the cardiac conduction system and its associated ganglia in FRDA. Whether these features are intrinsic to FRDA autonomic neurons has been untestable without a human cellular model. Here, a human model of FRDA autonomic neurons was established by differentiating induced pluripotent stem cells (iPSCs) from individuals with FRDA and from their CRISPR/Cas9-corrected isogenic controls. FRDA autonomic neurons expressed canonical autonomic lineage markers and retained reduced FXN mRNA and frataxin protein levels. Electrophysiological analysis revealed pronounced hyperexcitability, with an approximately five-fold increase in spike number, shortened interspike intervals, and longer bursts. FRDA autonomic neurons also exhibited increased cell death, elevated mitochondrial reactive oxygen species, and a shift from networked to tubular mitochondrial morphology. Bulk RNA sequencing of all three isogenic pairs revealed loss of extracellular matrix programs and activation of stress response pathways. The top differentially expressed gene was MEG3, a maternally imprinted long noncoding RNA, which was consistently upregulated across all three isogenic pairs. MEG3 sits within the imprinted 14q32 DLK1-DIO3 locus, whose maternally expressed noncoding transcripts were co-ordinately de-repressed in FRDA autonomic neurons. Competitive gene-set testing of 43 imprinted genes across 20 domains showed this to be specific to 14q32: no other imprinted domain was co-ordinately altered. Together, these findings establish hyperexcitability of autonomic neurons as a cell autonomous consequence of frataxin deficiency, accompanied by mitochondrial dysfunction. This provides a cellular basis for the increased sympathetic tone observed in clinical studies.

Neuroinflammation is increasingly recognized as a determinant of dopaminergic neuron vulnerability in Parkinson's disease, yet the receptor-level mechanisms linking microglia to disease progression remain incompletely defined. We investigated whether microglial P2Y12 receptor (P2Y12R) signalling drives neurodegeneration in experimental Parkinsonism and assessed its pharmacological tractability. Tamoxifen-inducible microglia-specific P2ry12 deletion was examined in acute and subchronic MPTP models, with receptor deletion induced before or during disease progression. Neurodegeneration, neuroinflammation, neurochemistry, and motor function were evaluated, and novel P2Y12R antagonists identified by structure-based virtual screening were characterized in vitro and following central administration in vivo. Inducible microglia-specific P2Y12R deletion reduced nigrostriatal dopaminergic neuron loss, preserved dopamine synthesis, attenuated acute and sustained neuroinflammatory responses, and improved parkinsonian motor deficits without affecting survival. Importantly, delayed receptor deletion during ongoing neurodegeneration remained protective, indicating that P2Y12R contributes to disease progression. Two novel antagonists exhibited functional P2Y12R inhibition in vitro, and central administration of the most promising candidate recapitulated the neuroprotective phenotype observed following genetic receptor deletion. These findings identify microglial P2Y12R as a therapeutically relevant regulator of neuroinflammation and dopaminergic vulnerability and provide complementary genetic and pharmacological proof-of-concept for targeting central P2Y12R in Parkinsonism.

The dentate gyrus (DG) is a critical regulator of cortical input processing in the hippocampus, supporting spatial navigation and memory processing. In epilepsy, the DG undergoes extensive structural and functional reorganization that diminishes its ability to filter afferent inputs, resulting in enhanced hippocampal hyperexcitability, seizures, and cognitive impairment. Yet, how DG network dynamics evolve over time in the epileptic brain is not fully understood. Here, we investigated DG network excitability, feedback inhibition, and throughput in rats 1 week, 8 weeks, and 4 months after pilocarpine-induced status epilepticus (SE), and examined the role of presynaptic GABAB receptor-mediated modulation of DG activity. Recording from urethane-anesthetized rats in vivo, we show a persistent increase in excitation-spike (E-S) coupling after SE. In contrast, feedback inhibition measured by short-duration paired-pulse ratios (PPR at 20ms, 40 ms and 60ms intervals) was significantly increased 1 and 8 weeks after SE, but was indistinguishable from controls by 4 months. Notably, we found that dentate spike (DS) frequency remained persistently elevated up to 10 months post-SE. Selective inhibition of presynaptic GABAB receptors in the DG using CGP36216 further enhanced E-S coupling at 1 and 8 weeks in post-SE rats without affecting age-matched controls. CGP36216 did not alter E-S coupling in rats 4 months after SE, revealing a homeostatic role for basal presynaptic GABAB signaling in restraining network excitability early after SE. CGP36216 robustly increased PPR at 20ms across all groups without altering DS frequency, suggesting that GABAB receptors boost DG feedback inhibition. Mechanistically, CGP36216 reduced single stimulus-evoked inhibitory postsynaptic currents (eIPSCs) in dentate granule cells without altering excitatory transmission after SE. Together, these findings support a disinhibitory role for presynaptic GABAB receptors, which bolsters synaptic inhibition to transiently counter post-SE hyperexcitability, and offers a targetable mechanism for therapeutic intervention during epileptogenesis.

C9orf72 encodes a protein that is important for both typical neurodevelopment and homeostatic processes across the lifespan. Pathogenic C9orf72 repeat expansions constitute the most common genetic cause of frontotemporal lobar degeneration (FTLD). Collectively, preclinical models and clinical neuroimaging studies have observed smaller thalamic volumes in C9orf72-associated FTLD, including in asymptomatic young adult C9orf72 repeat expansion carriers across 18 to 30 years old, supportive of potential neurodevelopmental origins. However, it is unknown whether asymptomatic young adult C9orf72 expansion carriers demonstrate volume differences in specific thalamic nuclei, as reported in older asymptomatic carriers and symptomatic patients; if so, normative transcriptomic patterns could reveal relevant neurodevelopmental and/or FTLD-related neurodegenerative processes. This study investigated volumetric MRI differences of the thalamic nuclei in asymptomatic young adult C9orf72 expansion carriers compared to non-carriers, and examined spatial associations with normative thalamic transcriptomics from 8 weeks post-conception through middle age. Young adult C9orf72 expansion carriers (n=72) and non-carriers (n=48) were enrolled in the Frontotemporal Dementia Prevention Initiative across Europe, Canada, and the USA (ages: 18-30 years; sex: 57% female). Spatial associations between young adult thalamic nuclei volumes and normative transcriptomics from the Allen Human Brain Atlas were examined using complementary data-driven and hypothesis-driven approaches. Spatial expression patterns of transcripts of interest were characterized across prenatal and postnatal neurodevelopment using BrainSpan data. Smaller volumes of the pulvinar, mediodorsal, and lateral nuclei were observed in young adult C9orf72 expansion carriers compared to non-carriers. These nuclei showed higher normative expression of transcripts involved concurrently in neurodevelopmental and C9orf72-associated FTLD neurodegenerative processes (including lysosomal, autophagic, and small GTPase functions), and lower normative expression of CALB1, a marker of prenatal human thalamic development. Normative expression of CALB2 (another human thalamic development marker) yielded positive correlations with C9orf72 across prenatal development to adulthood. These findings identify candidate transcripts that may provide insight into the molecular architecture leading to smaller thalamic nuclei volumes in C9orf72-associated FTLD.

Frontotemporal lobar degeneration (FTLD) encompasses clinically and biologically heterogeneous syndromes that are unlikely to be captured by a single blood biomarker. Although plasma neurofilament light (NfL) chain reflects neuroaxonal injury, multiplex profiling may identify complementary inflammatory, vascular and proteostatic processes relevant to clinical phenotype and progression. We characterised plasma CNS-related and inflammatory proteomic signatures across FTLD-related clinical syndromes and tested their associations with neuroaxonal injury, clinical severity, regional brain atrophy and survival. Plasma samples from 177 participants with behavioural variant frontotemporal dementia (bvFTD), primary progressive aphasia (PPA), progressive supranuclear palsy (PSP) or corticobasal syndrome (CBS) and 67 healthy controls were analysed using the high-sensitivity nucleic acid-linked immuno-sandwich assay (NULISA) platform. We quantified 130 CNS-related and 250 inflammation-related proteins. Differential expression and multivariate classification analyses were complemented by hierarchical clustering, penalised regression and survival analyses. Canonical correlation analysis tested multivariate associations between disease-associated proteins and regional MRI brain volumes. Sixty-one CNS-related and 61 inflammation-related proteins differed between participants with FTLD-related syndromes and controls after false-discovery-rate correction. NfL was the strongest individual discriminator between all patients and controls, with an area under the receiver operating characteristic curve of 0.91. In exploratory full-cohort models, the multivariate CNS signature achieved an area under the curve of 0.93, compared with 0.82 for the multivariate inflammation signature. However, inflammatory proteins provided stronger discrimination for selected syndrome comparisons, including PPA versus PSP. Among inflammation-related proteins, SPP1 and CD276 showed the strongest positive associations with NfL. Higher CD276 and SPP1 were associated with increased mortality, whereas higher amyloid-{beta}42 was associated with lower mortality. A multivariate protein signature weighted towards tumour necrosis factor and immune signalling was associated with lower regional brain volumes across predominantly frontotemporal and limbic regions (canonical correlation 0.43; permutation p=0.018). Plasma multiplex proteomics identified complementary dimensions of neuroaxonal injury and immune dysregulation across frontotemporal lobar degeneration-related syndromes. CNS-related proteins, particularly NfL, predominantly captured case-control neurodegeneration, whereas inflammatory signatures provided additional information about syndrome heterogeneity, structural brain changes and survival. SPP1, CD276 and broader immune-related signatures are candidates for independent biomarker validation and mechanistic investigation.

Recent evidence implicates somatic mutations in disease-associated genes across multiple neurodegenerative disorders, including the identification of two somatic TARDBP variants as a putative cause of frontotemporal lobar degeneration with TDP-43 pathology type C (FTLD-TDP type C). However, these findings remain anecdotal. We performed single-nucleus amplicon sequencing of 39,800 neurons from the superior temporal gyrus of sporadic FTLD-TDP type C patients (34,738 neurons, 52 individuals) and non-demented controls (5,062 neurons, 26 individuals) using the Mission Bio Tapestri platform and investigated somatic variants in TARDBP and other FTLD-TDP-associated genes in a case-control setting. We uncovered an extensive landscape of ultra-low-frequency (<1%) somatic mutations across all analysed genes, including TARDBP. Rare somatic occurrences of known ALS/FTD-associated germline TARDBP variants, including p.N267S and p.M337V, were identified exclusively in patients. Among all targeted genes, TARDBP had the highest proportion of neurons harbouring a somatic variant, and this mutational burden was lower in individuals who died at an older age. Strikingly, the C-terminal domain of TDP-43, where most ALS/FTD germline pathogenic variants reside, exhibited a lower neuronal mutational burden than its other domains. This suggests that neurons harbouring damaging mutations may undergoprogressive loss prior to autopsy, leaving only rare survivors at frequencies too low to detect by bulk or small-scale single-cell approaches. Together, our findings provide an unprecedented resolution into the somatic mutational landscape of post-mitotic neurons in FTLD-TDP type C and reveal a gene-specific layer of neuronal mosaicism that current single-cell WGS studies fail to detect.

The Vanishing White Matter (VWM) Registry is a single-center database containing longitudinal survey data from >470 untreated patients with DNA- and MRI-confirmed VWM. VWM is a rare genetic disorder of the brain's white matter with an estimated live birth incidence of 1 per 100,000 and prevalence of 1.3 per 1,000,000 people in the Netherlands. The Registry represents a remarkably extensive collection of systematically gathered information on this disease, enabling crucial research into the natural history of VWM and providing a valuable resource for control arms in clinical trials. Data, initially collected on paper from 2004, have been maintained electronically since 2018, and include validated scales alongside a disease-specific customized questionnaire covering clinical, functional, and psychosocial domains. Survey packages, available in eight languages, are sent one to four times a year, depending on patient age. Built-in validity checks and review by pediatric and adult neurologists ensure data quality. The dataset is continuously updated with questionnaires expanding its scope, and structured for analysis and reuse in research on VWM.

The majority of Parkinson's disease patients suffer from decreased tactile acuity or neuropathic pain, both of which contribute to low quality of life and likely exacerbate motor dysfunction. How Parkinson's disease pathology relates to altered somatosensation remains unclear. One potential contributor is the progressive degeneration of dopamine neurons. To assess the extent to which gradual dopamine neuron loss contributes to altered somatosensation, we recorded spontaneous and stimulus-evoked activity in the primary somatosensory cortex of the MitoPark mouse model of Parkinson's disease. MitoPark mice experience progressive dopamine neuron degeneration that is independent of -synuclein. We found that MitoPark layer V regular-spiking (largely pyramidal) neurons, but not fast-spiking (largely parvalbumin-expressing inhibitory) neurons, had elevated spontaneous firing rates relative to littermate controls at late stages of symptom progression. Regular-spiking neurons also became hyperresponsive to tactile stimuli -- more neurons were recruited by stimuli across a wide range of intensities, and these neurons responded with higher firing rates. Fast-spiking neurons, but not regular-spiking neurons, became desynchronized at late stages of symptom progression. These physiological changes coincided with pronounced degeneration of dopamine neurons and axons, which we measured with tyrosine hydroxylase immunostaining in the midbrain, striatum, and primary somatosensory cortex. Altogether, this characterization revealed cell-type-specific changes in the primary somatosensory cortex that are consistent with both decreased tactile acuity and hyperalgesia in Parkinson's disease patients. This suggests that the loss of dopamine neurons, potentially including those that innervate primary somatosensory cortex, contributes to somatosensory impairments associated with Parkinson's disease.

Axonal degeneration is a principal driver of irreversible neurological disability in multiple sclerosis (MS), yet current treatments fail to target this neurodegenerative phase directly. Sterile alpha and TIR domain-containing protein 1 (SARM1) has emerged as an executioner of programmed axon destruction and is overexpressed in grey and white matter MS tissue, making its inhibition a promising therapeutic strategy. However, the effects of SARM1 inhibition on localized neurodegeneration versus systemic and central inflammation remain poorly understood in complex autoimmune environments like MS. Here, we investigated SARM1 pathology using global SARM1-/- knockout (SARM1-/-) mice, AAV-mediated CRISPR knockdown and overexpression of SARM1 in retinal ganglion cells (RGCs), and the small-molecule SARM1 inhibitor 5-iodoisoquinoline (5IIQ), across optic nerve crush (ONC) and experimental autoimmune encephalomyelitis (EAE) models. While global SARM1-/- did not alter the overall clinical course of EAE, it revealed a complex phenotype characterized by an altered peripheral inflammatory cytokine profile and persistent CNS immune infiltration, alongside preserved axonal and myelin integrity. RGC-restricted SARM1 knockdown partially preserved RGCs and axons during EAE, whereas SARM1 overexpression worsened both retinal function and axonal injury. Pharmacological inhibition with 5IIQ preserved axonal integrity and restored visual function in both the ONC and EAE models, as confirmed by electrophysiology, and reduced serum neurofilament light chain (NfL) in EAE, without affecting demyelination. Together, these findings demonstrate that SARM1 inhibition uncouples axonal self-destruction from demyelination and gross neuroinflammation while providing robust structural and functional neuroprotection. This study establishes SARM1 as a viable target for neuroprotective co-therapies designed to complement existing immunomodulatory and remyelinating regimens in MS and related neurodegenerative disorders.

Brain tumors interact with adjacent neural circuits, with tumor infiltration altering neural physiology, and aberrant neuronal activity, in-turn, promoting tumor growth. Due to limited patient numbers, variable recording methods, and tumor heterogeneity, direct evidence of electrophysiologic distinctions between specific tumor types and these interactions in the intact human brain is lacking. Here, we analyzed intraoperative recordings from 100 participants undergoing tumor resection, epilepsy surgery, or movement disorder deep brain stimulator implant surgeries using clinical electrocorticography (ECoG), mesoscale ECoG, and high-density micro-ECoG. Tumor cases included IDH-mutant (IDHm) gliomas across grades, IDH-wildtype (IDHwt) glioblastomas, and metastases. Multiscale neurophysiological activity was spatially mapped to patient-specific tumor and brain anatomy, enabling direct assessment of physiological changes across the tumor-brain interface. Our findings show that population-averaged electrophysiological measures alone provide limited diagnostic separation, whereas spatially-resolved analyses reveal robust physiological gradients linked to tumor distance. Measures of excitatory-inhibitory balance, particularly aperiodic exponent and high-gamma activity, varied systematically with tumor proximity and correlated with local tumor volume fraction around individual electrode contacts. These relationships were detectably different between infiltrative glioma (both IDHwt and IDHm) and metastases, even across recording scales. Furthermore, functional connectivity revealed specific patterns of network organization with the infiltrative glioma cohort, clearly separating IDHwt and IDHm. Beta band coherence between the tumor and brain was significantly reduced in IDHm compared to within the tumor or within brain connectivity (p=0.0006; Kruskal-Wallis test ; mean coherence tumor-brain: 0.26, tumor-tumor: 0.44; brain-brain: 0.34), a pattern not seen in IDHwt or metastases.. Physiological abnormalities extended into radiographically normal-appearing brain. Together, these findings reveal spatially organized, tumor type-dependent physiological signatures of tumor-brain interactions in the intact human brain. Electrophysiology may therefore provide a dynamic physiological map of the tumor-brain interface that complements structural imaging.