Neurology Genetics

Background: Neurological, neuropsychiatric, and neurodevelopmental disorders cluster in ALS families, sharing a common genetic architecture with ALS. Pathogenic variants in genes associated with other neurological, neurodevelopmental, or neuropsychiatric disorders may also co-occur in ALS and modify phenotype. We have sought to determine the prevalence and clinical pattern of likely-pathogenic/pathogenic (LP/P) non-ALS neurological, neurodevelopmental, and neuropsychiatric variants, alone and in combination with ALS-gene variants, in two large ALS cohorts. Methods: Whole-genome sequencing (WGS) of 469 Irish and 774 Answer ALS people with ALS (pwALS) was analysed for ClinVar LP/P variants associated with other neurological (n = 15541), neurodevelopmental (n = 9761), and neuropsychiatric (n = 321) phenotypes. Inheritance patterns for associated genes (autosomal recessive/autosomal dominant) along with the associated phenotype were validated using OMIM. Standardised clinical data included family history, site and age of onset, El Escorial category, survival, motor decline, and cognitive and behavioural assessments. Known ALS-gene variants and C9orf72 repeat expansion status were included for each cohort. Results: Non-ALS neurological variants were identified in 47/469 (10.0%) Irish and 69/774 (8.9%) Answer ALS participants, most frequently in hereditary spastic paraplegia-associated genes (3.2% Irish; 2.8% Answer ALS). Irish neurological variant carriers showed higher frequency of respiratory onset (10.6% vs 1.2%, Fisher's exact p = 0.002, {Phi} = 0.20) and fewer premorbid behavioural symptoms (0.92 +/- 0.56 vs 3.08 +/- 0.97, Cohen's d = -0.40). Neurodevelopmental variants occurred in 12/469 (2.6%) Irish and 20/774 (2.6%) Answer ALS participants. In the Irish cohort, neurodevelopmental variant carriers had significantly shorter survival in Cox proportional hazards model (log-rank p = 0.005), corresponding to a more than two-fold increased hazard of death (HR = 2.25, 95% CI 1.26-4.00), and had significantly increased familial burden of neuropsychiatric disorders among first- and second-degree relatives (negative binomial IRR for carriers = 2.41, 95% CI: 1.12-5.18, p = 0.025). Across combined cohorts, 18 individuals (Irish n = 8; Answer ALS n = 10) carried [≥]2 LP/P variants spanning ALS and non-ALS genes. Conclusion: Rare LP/P variants in genes associated with other neurological and neurodevelopmental disorders occur in up to 12% of pwALS across two independent cohorts. Carriers show distinct phenotypes, shorter survival, and characteristic family history patterns. These findings suggest that extended pleiotropic and oligogenic architectures may contribute to ALS heterogeneity.

A molecular diagnosis remains out of reach for a substantial subset of patients with clinically recognizable Mendelian disorders, even after comprehensive next-generation sequencing. Causal variants in non-coding regions are difficult to detect and interpret using standard pipelines. Deep intronic variants that disrupt splicing are a known but underexplored source of pathogenic alleles, and systematic tools to evaluate them at scale have only recently emerged. We aimed to resolve an incomplete genetic diagnosis in two siblings with early-onset parkinsonism, prominent neuropsychiatric features, and autonomic dysfunction consistent with PLA2G6-associated neurodegeneration (PLAN), an autosomal recessive condition. Prior clinical exome sequencing, genome sequencing, Multiplex Ligation-dependent Probe Amplification (MLPA), and long-read sequencing had identified only a single heterozygous PLA2G6 missense variant, c.2132C>G (p.Pro711Arg). We used AlphaGenome to score 91 non-coding variants shared among the affected siblings and their father within 1 megabase of the PLA2G6 locus. The deep-learning model identified an intronic variant (c.2034+355G>A) that was predicted to create a cryptic splice acceptor site that could result in inclusion of a 160-bp cryptic exon. Tissue-specific predictions indicated the aberrant splicing would be detectable in blood, confirmed by junction-spanning RNA-seq reads from an unrelated carrier. This analysis completed a compound heterozygous PLAN diagnosis nearly two decades after symptom onset and demonstrates the utility of sequence-to-function models. Systematic integration of tools like AlphaGenome into rare disease workflows offers a practical, low-barrier route to closing the diagnostic gap for patients with compelling Mendelian phenotypes and incomplete genetic diagnoses.

INTRODUCTION: We integrate visual and quantitative metrics in white matter and medial temporal lobe to examine relationships with neuropathology in a community cohort. METHODS: Postmortem in situ MRI (T1, T2, DWI) was performed in 25 human brains, followed by visual ratings (Fazekas, MTA, ERICA, Koedam). Neuropathology included ADNC, LATE-NC, hippocampal sclerosis, PART, ARTAG, Lewy pathology, and CAA. RESULTS: Increased Fazekas score was linked to aging, lower education, hypertension, higher basilar artery wall thickness, and greater Braak NFT stage. WMH volume also correlated with lacunes, Thal phase, and CERAD score that was not observed using Fazekas. Hippocampal volumes were lower in elderly, less educated people and were associated with higher atrophy scores and higher Braak NFT stage. Higher amygdala volume was only associated with higher CERAD score. DISCUSSION: Quantitative MRI may detect neuropathologic associations more sensitively than visual ratings. Tau pathology is a key predictor of WMH burden and hippocampal atrophy.

Background: LRRK2 variants are major contributors to Parkinsons disease (PD). Many pathogenic variants increase kinase activity, underscoring the value of functional assays in nominating therapeutic targets and kinase inhibitors as potential disease-modifying therapies. Objective: To develop an interactive resource that provides functional context and ancestry-specific variant frequencies. Methods: Genotyping and short-read sequencing data were analyzed for 101,678 individuals (61,709 PD, 39,969 controls) from the Global Parkinsons Genetics Program (GP2) and integrated with clinical and in-vitro biochemical kinase activity information. Results: The LRRK2 Browser (http://gp2.org/lrrk2browser) displays ancestry-specific genetic data for 19,596 LRRK2 variants (968 exonic, 14 disease-associated) across 11 populations, and functional data for 171 variants. Clinical annotations include age, age at onset, and family history of PD. Discussion: The publicly available LRRK2 Browser represents an open-access, multi-ancestry resource to support LRRK2 variant interpretation. It aims to enhance the translational potential of genetic and functional data for precision medicine and the implementation of gene-targeted therapies in diverse populations.

Background and Objectives: Deep sequencing of brain tissue in the research setting has established that mosaic variants are a major cause of malformations of cortical development (MCDs) and epilepsy. However, genetic testing in the clinical setting primarily detects germline variants using clinically accessible samples. We aimed to determine the diagnostic yield and clinical utility of deep sequencing in the clinical setting to identify pathogenic mosaic variants for this population. Methods: We performed a retrospective cohort analysis of individuals at Boston Children's Hospital with MCDs with or without epilepsy who received clinical deep sequencing between September 2017 and February 2026. Demographic, clinical, and genetic testing data were abstracted from the medical record. For individuals without systemic features, we classified brain tissue as an affected tissue sample. For individuals with systemic features, we classified brain or relevant non-brain tissue as affected. The primary outcome was the diagnostic yield of clinical deep sequencing performed using affected vs unaffected tissue samples. The secondary outcome was the clinical utility of genetic diagnoses. Results: Our cohort included 37 individuals (19/37 (51%) female, 18/37 (49%) male) with MCDs, of whom 35/37 (95%) had epilepsy (25 with brain tissue samples available from epilepsy surgery) and 8/37 (22%) had systemic features. Most (35/37 (95%)) had dysplasia phenotypes on MRI and 12/27 (44%) with pathology available had Focal Cortical Dysplasia Type I or II. The diagnostic yield was 53% (17/32; 16 mosaic and 1 germline variant) when clinical deep sequencing was performed using an affected tissue sample vs 0% (0/6) using an unaffected tissue sample (p=0.016). Of the diagnosed cases, 13/17 (76%) had testing performed on brain tissue (1 with systemic features) and 4/17 (24%) on non-brain tissue (3 buccal and 1 duodenal tissue, all with systemic features). All but one diagnosis involved the mTOR pathway. All diagnoses had clinical utility. Discussion: Clinical deep sequencing, when performed using an affected tissue sample, has high diagnostic yield and clinical utility for individuals with MCDs, especially dysplasia phenotypes, and epilepsy. Our findings support implementation of clinical deep sequencing for this population, especially as the genetic diagnoses have implications for emerging precision therapies.

Cerebrovascular pathology is increasingly implicated in neurodegenerative diseases, yet its pathomechanistic contribution remains poorly defined. Building on prior evidence of dysregulated iron and oxygen homeostasis in early-affected brain regions of progressive supranuclear palsy (PSP), we hypothesized that brain microvascular alterations may play an etiological role in select neurodegenerative proteinopathies. First, we conducted a systematic neuropathological evaluation of 178 brains from the University Health Network Neurodegenerative Brain Collection, including Alzheimers disease-related neuropathologic change (ADNC; n=30), Lewy body disease with high or intermediate ADNC (n=38) and low ADNC (n=16), multiple system atrophy (MSA; n=14), PSP (n=39), frontotemporal lobar degeneration with TDP-43 proteinopathy (FTLD-TDP; n=10), and controls (n=31). Arteriolosclerosis, microinfarction, and calcification were assessed in the basal ganglia and frontal cortex. Iron burden was correlated by quantification of Perls staining in MSA and PSP, where vessel pathology was most severe. Single-nucleus RNA-sequencing (snRNA-seq) of frontal cortex tissue from control (n=5) and PSP (n=8) cases with varying arteriolosclerosis severity was performed to characterize the vascular transcriptome, with validation against an independent snRNA-seq evaluation of PSP (n= 11), Picks disease (n=9), AD (n=10), and control (n=10) brains. Histological analysis revealed disease-specific involvement of microvascular pathology in neurodegenerative diseases, identifying PSP to demonstrate most prominent and widespread vessel wall thickening across regions examined. Regression analysis using demographic, APOE and MAPT genetic risk status, and neuropathological features of cases corroborated the distinct association with PSP pathology. Elevated iron load in early affected regions of MSA and PSP brains correlated with greater vessel wall thickening, suggesting a possible pathomechanistic relationship between the two disease physiologies. snRNA-seq analysis of vascular transcriptome identified robust upregulation of heat shock proteins and hypoxia-related genes in PSP endothelial cells and pericytes across both datasets. Importantly, we found the proteotoxic signature to be strongly associated with higher vessel scores in PSP cases, linking microvascular morphology to endothelial dysfunction. Our comprehensive neuropathological evaluation coupled with correlative snRNA-seq analysis establish PSP-specific arteriolar thickening associated with endothelial proteotoxic state as a candidate pathogenic mechanism. The cerebral arteriolar unit represents a compelling therapeutic target for disease modification in PSP.

Introduction: Variants in the polymerase gamma (POLG) gene are associated with a wide range of mitochondrial disorders. Emerging evidence suggests a potential link between POLG variants and Parkinson's disease (PD); yet, results remain inconclusive. Objectives: To investigate the genetic spectrum and prevalence of POLG variants in PD across diverse ancestries. Methods: We leveraged multi-ancestry genetic data from the Global Parkinson's Genetics Program (GP2), including genotyping data from 98,589 and short-read sequencing data from 36,022 individuals. We performed a POLG rare variant screen, case-control association, and gene-level burden analyses. Results: Five PD cases carried potentially biallelic rare pathogenic/likely pathogenic POLG variants. Additionally, 228 individuals (<1%; 161 PD cases, 28 individuals with other neurological disorders, and 39 controls) carried 34 distinct rare pathogenic/likely pathogenic heterozygous variants, with no significant frequency differences between cases and controls, except for the p.Ala467Thr variant in the European population. The co-inherited pathogenic variants p.Thr251Ile and p.Pro587Leu were present in <1% of both cases and controls, with no significant group differences. Burden and variant-level association analyses showed no association between rare POLG variant burden or common POLG variant enrichment and PD. Conclusions: POLG variants are overall rare in PD. The identification of rare pathogenic variants among PD cases suggests that POLG-related mitochondrial dysfunction may contribute to PD in isolated instances, particularly under recessive inheritance. Our findings support a role for POLG variants in select cases and underscore the need for larger-scale sequencing and functional studies.

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease characterised by progressive motor neuron loss and corticospinal tract degeneration. The genetic landscape of ALS is complex, with increasing recognition of shared genetic and phenotypic features with other neurodegenerative conditions, particularly those involving repeat expansions. Given that repeat expansions in disorders like spinocerebellar ataxia type 27B (SCA27B), caused by an intronic GAA repeat expansion in Fibroblast Growth Factor 14 (FGF14), are recognised to extend beyond cerebellar ataxia with frequent pyramidal signs, we hypothesised that FGF14 repeat expansions might also contribute to ALS and degeneration of corticospinal pathways, and sought to investigate whether repeat length is associated with clinical phenotype. We screened 62 individuals with ALS using PacBio HiFi long-read whole-genome sequencing and compared repeat-size distributions with 256 healthy controls from the Human Pangenome Reference Consortium. Repeat expansions were confirmed using flanking PCR and repeat-primed PCR. We identified pathogenic-range FGF14 GAA [&ge;]250 expansions, the established threshold for SCA27B, in 3/62 ALS cases (4.8%) and none in controls. Further analysis revealed that GAA expansions [&ge;]200 repeats were enriched in ALS compared to controls (8.1% vs 0.4%; p = 0.0013), suggesting a broader pathogenic spectrum for FGF14 GAA repeats in ALS. In contrast, GAAGGA expansions were not significantly associated. Expanded pure GAA alleles were predicted to form triplex (H-DNA) structures, with the repeat-containing isoform (1B) being the predominant FGF14 transcript in motor neurons. These findings demonstrate that FGF14 GAA repeat expansions extend into the motor neuron disease spectrum.

Expanded short tandem repeats contribute to a broad spectrum of neurodegenerative diseases, yet their roles in Parkinson's disease (PD) and parkinsonism remain incompletely characterized, especially across diverse ancestries. We analyzed short-read whole-genome (WGS) and clinical exome sequencing (CES) data from 38,365 individuals (28,861 WGS; 9,504 CES), encompassing 23,242 patients with PD, 4,729 patients with atypical parkinsonism and 10,394 healthy controls from 11 genetic ancestries. To determine carrier frequencies and characterize repeat structures across diverse ancestries, we genotyped 12 established pathogenic loci where normal, intermediate, and pathogenic alleles can be reliably differentiated using short-read sequencing data. Additionally, we conducted threshold-based associations to determine the minimum threshold associated with increased PD risk in 15,995 individuals (8,591 PD, 7,404 controls) of European ancestry. Pathogenic repeat expansions were detected in 62 patients (56 PD and 6 atypical parkinsonism) and 5 controls across seven loci (AR, ATXN1, ATXN2, ATXN3, CACNA1A, HTT and THAP11), spanning seven ancestries. Among these, ATXN2 expansions were the most frequently observed in PD and were present in African, East Asian, European and Middle Eastern ancestries. Additionally, intermediate ATXN2 repeat expansions exhibited a strong, length-dependent association with PD risk in the European population, with individuals with [&ge;]32 repeats having a more than four-fold increased risk (odds ratio 4.25, 95% confidence interval 1.80-12.05). Overall, >92% of expanded alleles harbor CAA interruptions within the CAG tract. Pathogenic expansions at other loci, such as ATXN3 and THAP11, showed more ancestry-specific distributions. Clinically, individuals with pathogenic ATXN2 and ATXN3 expansions most often presented with typical PD features but frequently showed earlier disease onset and a strong family history of PD. This large-scale, multi-ancestry study comprehensively maps the genetic landscape of pathogenic and intermediate repeat expansions in PD. Our findings confirm a length- and structure-dependent risk association for ATXN2 with PD in the European population, and highlight the pleiotropic effects of repeat expansions across the parkinsonian spectrum.

Background: The Progressive Supranuclear Palsy Clinical Deficits Scale (PSP-CDS) is a brief rating scale of clinical severity in PSP. However, its longitudinal performance has not been evaluated. We aimed to assess the ability of the PSP-CDS to track disease progression over time and to compare progression across PSP phenotypes in a real-world Asian cohort. Methods: Patients who met the Movement Disorder Society PSP diagnostic criteria and underwent at least 2 PSP-CDS assessments were recruited from movement disorders clinics in Malaysia. Longitudinal progression was evaluated using linear mixed-effects models. Domain-specific progression and subtype-specific trajectories were also analyzed. Associations between annualized changes in PSP-CDS and Barthel Index (BI) scores were examined. Results: 104 patients (including 59 with PSP-Richardson's syndrome [PSP-RS], 28 with predominant parkinsonism [PSP-P], and 14 with progressive gait freezing [PSP-PGF]) contributed 394 PSP-CDS assessments over a median follow-up of 33.2 months (range, 8.7-73.1 months). PSP-CDS scores increased significantly over time ({beta}=0.126 points/month), corresponding to estimated increases of 1.13 points over 9 months and 2.27 points over 18 months. Subtype-specific analyses demonstrated the fastest progression in PSP-RS (0.156 points/month), followed by PSP-PGF (0.081 points/month) and PSP-P (0.077 points/month). Exploratory domain-level analyses showed that finger dexterity, communication, and dysphagia were the most rapidly worsening domains. Annualized PSP-CDS progression correlated significantly with annualized decline in BI scores (Spearman's {rho}=-0.474, P<0.001). Conclusions: The PSP-CDS is sensitive to longitudinal disease progression in PSP and captures clinically-meaningful functional decline. Its brevity and ability to distinguish differential progression across PSP phenotypes support its utility as a pragmatic outcome measure for routine clinical practice and research.

A major obstacle for clinical trials is the lack of objective, sensitive, and reliable measures that can detect modest changes in disease progression. Here, we determine whether acoustic and linguistic digital speech measures automatically obtained during a functionally relevant passage-reading task capture multiple dimensions of disease in ataxia, including functional communication impairment, subclinical cerebellar dysfunction and disease progression. A total of 157 individuals with ataxia and 84 controls contributed cross-sectional data, and 54 individuals with ataxia and 43 controls contributed longitudinal data within the ongoing Neurobooth natural history study. Participants completed standardized speech recordings, patient-reported outcome measures (PROMs) and neurologist-rated clinical evaluations. A novel speech processing pipeline was developed to automatically transcribe audio recordings, identify word boundaries and extract a predefined set of linguistic and within-word acoustic features. Individuals with ataxia exhibited marked disruption of speech timing, coordination and articulatory control, including slowed speech (d=1.23), prolonged inter-word pauses (d=-0.91), higher/more variable vocal intensity (|d|=0.43-0.51) and altered spectral content (|d|=0.43-0.79) compared to healthy controls. Linguistic features (e.g. speaking rate and within-word pause duration) showed strong associations with clinician-rated severity and PROMs (|r|=0.23-68), indicating alignment with functional communication impairment and patient-perceived disease burden. In contrast, acoustic features derived from cepstral measures captured subtle abnormalities in speech motor control, differentiating not only individuals with ataxia (d=0.65) but also pre-ataxic individuals (d=0.56), and those without clinically evident dysarthria (d=0.45), from controls. These findings indicate that acoustic features reflect subclinical cerebellar motor dysfunction involving impaired temporal coordination and vocal control before overt clinical speech impairment emerges. Longitudinally, several acoustic measures were sensitive to disease progression (MSDR=0.19-0.68), even in cases where clinical scales showed no detectable change. Speech-derived changes correlated with changes in clinical scales and PROMs. Both acoustic and linguistic features exhibited strong intra-session reliability. During passage reading, acoustic and linguistic measures provide complementary but different clinical information in ataxias. Linguistic measures primarily reflect downstream functional consequences of ataxic dysarthria, whereas acoustic measures provide sensitive indicators of subclinical cerebellar motor dysfunction and progression. These findings demonstrate that natural speech analysis can produce digital measures for detecting subclinical disease, quantifying functional impairment, monitoring progression in ataxia, with strong potential for application in clinical trials and remote monitoring.

Importance: With emerging gene-targeted therapies in amyotrophic lateral sclerosis (ALS), gene discoveries and genetic diagnoses provide a crucial path to treatment. Pathogenic variants with moderate effect or incomplete penetrance, however, remain unidentified in genome-wide association studies and can appear sporadic in small modern-day pedigrees. Lack of recognition of familial clustering of ALS, in turn, limits opportunities for gene discovery, genetic diagnosis, risk counseling, and treatment. Objective: To determine the power of automated reconstruction of extended pedigrees, integrating archive records and genetic relatedness, in gene-discovery studies. Design: Retrospective observational study of Dutch ALS patients with the C9orf72 hexanucleotide repeat expansion (HRE), combining clinical family history, civil records, and genome-wide genotyping for relatedness and identity-by-descent (IBD) inference. Setting: National, population-based ALS cohort from the Netherlands and digitized population archives enabling systematic reconstruction of extended pedigrees. Participants: Individuals with ALS and a confirmed C9orf72 HRE. Participants must have provided a clinical family history and traceable Dutch ancestry documented in population archives. Main Outcomes and Measures: The primary outcome was the proportion of C9orf72 HRE carriers with newly identified (distant) relatives with ALS compared with clinical family history. The secondary outcome was the precision of IBD-based methods to fine-map the C9orf72 HRE. Other outcomes included phenotypic similarities between distantly related patients. Results: Among 238 C9orf72 HRE carriers, 91 could be included in one of 39 extended pedigrees dating back to ~1800, with relationships up to the eighth degree of relatedness. Compared with clinical family history alone, our approach increased the number of identified relationships by 2.5-fold. Genome-wide IBD analysis revealed shared haplotypes encompassing the C9orf72 HRE in 94% of pedigrees by [&ge;]7 meioses in 25.7-127.8 centimorgans total IBD shared. Conclusions and Relevance: Large-scale interrogation of archives facilitates reconstruction of extended pedigrees for ALS patients carrying the C9orf72 HRE. This combined genealogical-genetic approach supports the reclassification of apparently sporadic cases, facilitates the discovery of new disease-causing variants in ALS, and is generalizable to other late-onset neurodegenerative diseases. Automated pedigree reconstruction from genealogical data and visualization in an interactive databrowser are implemented in the open-source Mangrove software.

Background. Three disease-modifying therapies (DMTs) for spinal muscular atrophy (SMA) have been approved since 2016, yet many adults remain untreated. Identifying them depends on ICD-10 codes that capture SMA but do not reliably distinguish it from other related conditions. We examined, in one U.S. health system, both patients' engagement with therapy and the accuracy of the codes used to find them. Methods. We conducted a retrospective chart review of adults in an academic health system identified by SMA-associated ICD-10 codes, with manual adjudication of diagnosis and DMT status. Confirmed SMA-positive, DMT-naive patients were invited to a structured telephone interview on treatment awareness and barriers. Results. Of 60 charts, 22 (36.7%; 95% CI 25.6-49.3%) were appropriately coded for SMA or a related disorder; only 16 (26.7%) had molecularly confirmed SMA. The other 38 (63.3%) were miscoded, spanning spinal and bulbar muscular atrophy, asymptomatic carriers, prenatal screening, and conditions unrelated to SMA. Ten of the 16 confirmed patients (62.5%) were DMT-naive; one was interviewed, one declined, and eight could not be reached. The non-response is itself a finding: the patients least visible to administrative data are the hardest to reach. Conclusions. ICD-10 ambiguity is a barrier to treatment access in adult SMA, as is loss to follow-up. We make two recommendations: continuous documentation-coding alignment that uses natural language processing to verify the genetic precondition, and type-specific SMA codes (subcodes for Types 0-4) anchored on molecular SMN1 confirmation. Together these would support cohort identification, outreach, and evidence generation without adding to clinician burden.

Background and Objectives To investigate the associations of blood-based tau biomarkers with clinical, electrophysiologic and prognostic measures in amyotrophic lateral sclerosis (ALS), and to determine whether they reflect distinct disease-related processes. Methods We studied 119 patients with ALS from a longitudinal observational cohort. Plasma and serum p-tau181, p-tau217, p-tau231, brain-derived tau (BD-tau), NfL and GFAP were measured using Lumipulse and Simoa assays. Associations with demographic variables, disease severity (ALSFRS-R and slow vital capacity), lower motor neuron (LMN), muscle involvement (creatine kinase [CK] and high-sensitivity cardiac troponin T [hs-cTnT]), disease progression and survival were assessed using multivariable models. Results Tau-related biomarkers, specifically p-tau217 and BD-tau, were associated with greater cross-sectional disease severity, reflected by lower ALSFRS-R scores. Plasma and serum p-tau181, p-tau217, p-tau231, and BD-tau were associated with higher CK and hs-cTnT, whereas p-tau181 and p-tau231 were also associated with greater LMN involvement. In contrast, NfL and GFAP were not associated with muscle or LMN involvement. Across analytical platforms, plasma and serum NfL were associated with faster ALSFRS-R decline and shorter survival. NfL was the only biomarker independently associated with both disease progression and survival. Discussion Blood biomarkers capture distinct dimensions of ALS. Tau-related biomarkers are associated with cross-sectional disease severity, LMN involvement and muscle injury, whereas NfL primarily reflects disease progression and survival. These findings support the complementary use of tau-related biomarkers and NfL for ALS phenotypic characterization and prognosis assessment.

Parkinson's disease (PD) exhibits pronounced sex differences, yet the underlying genetic and molecular mechanisms remain poorly understood. We performed the largest-to-date meta-analysis of sex-stratified genome-wide association studies of PD followed by brain proteogenomics-based causal inference analyses. We nominated 10 candidate proteins that appear important to sex-biased PD risk, of which 2 female-biased, GALC and PSMG1, and 3 male-biased, ACTR1B, WDR41, and CD151, were most robustly prioritized. Together, our findings provide evidence for genetic sex differences in PD, prioritizing sex-biased proteins implicated in lysosomal regulation, neuroinflammation, lipid biology, and other PD-relevant mechanisms, and highlighting potential sex-informed therapeutic opportunities.

Bi-directional maternal-fetal exchange during pregnancy creates a long-term microchimerism (Mc) legacy in both individuals, but its presence and cellular fate in human brain are largely unknown. We studied surgically resected epilepsy brain specimens with targetable maternal polymorphisms using polymorphism-specific quantitative PCR. Maternal Mc was prevalent, detectable in 70% of patients, and often at striking quantities spanning temporal, frontal, parietal, and hippocampal regions. Next, we employed single nucleus RNA profiling using cellector, a genetic demultiplexing tool designed to detect rare allogeneic cells. We identified Mc across major neural and glial populations. Finally, analysis of publicly available snRNA-seq datasets from neurotypical brains from gestation to late adulthood further revealed widespread Mc, persisting into advanced age, and preferentially adopting L2/3 intratelencephalic neuronal or microglial/macrophage-like fates. These data show that naturally acquired Mc is prevalent, diverse, and persistent in human brain, inviting reconsideration of what constitutes "self," with broad implications for health and disease.

Background: Neurofilament light chain (NfL) gained FDA recognition in amyotrophic lateral sclerosis (ALS) through SIMOA-based validation, where baseline serum NfL predicts ALSFRS-R slope and survival, and through the 2023 tofersen approval for SOD1-ALS. The commercial Roche Elecsys electrochemiluminescence immunoassay (ECLIA) reads 6- to 8-fold lower than SIMOA, and its clinical utility in ALS is uncharacterized. We assessed whether ECLIA NfL retains this correlation in routine care and whether GFAP or S-100B helps. Methods: Retrospective analysis of 58 chart-confirmed ALS patients at Georgetown University Hospital (2022-2026), biomarkers on the LabCorp Roche Elecsys ECLIA. The NfL-ALSFRS-R correlation was assessed where both measures fell within matching windows; serial NfL, in patients with repeat draws. Results: First-per-patient NfL median was 7.06 pg/mL (IQR 4.06-17.30; CV 99%). Among 31 patients with matched NfL and ALSFRS-R decline rates, Spearman r = 0.704; within 90 days (n = 17), r = 0.809 (both p < 0.0001). Fast progressors (n = 8) had mean NfL 17.10 pg/mL versus 4.64 in slow progressors (n = 21), a 3.7-fold separation. Serial NfL captured rising trajectories and stable low values. GFAP rose within patients but tracked neither progression rate, disease stage, nor motor-neuron predominance; S-100B added no value. Conclusions: Commercial ECLIA brings NfL into routine ALS care; its prognostic correlation with progression rate survives real-world fragmentation. The actionable unit is the longitudinal trajectory, not the single value, read against platform-specific reference ranges and clinical context (genotype, onset, stage). GFAP and S-100B add little. Keywords: amyotrophic lateral sclerosis, neurofilament light chain, biomarkers, implementation science, ECLIA, GFAP, monitoring, tofersen, real-world data

Parkinsons disease (PD) arises through disruption of multiple interconnected cellular processes, but the genetic contributions to these processes may differ across ancestries. We investigated functional convergence among genes harboring pathogenic or likely pathogenic (P/LP) variants and variants of uncertain significance (VUS) in a multicenter Indian cohort recruited through the Genetics of Parkinsons Disease in India Young Onset Parkinsons Disease project (GOPI YOPD). The cohort included 668 participants (463 males 69.3%) with a mean age at motor onset of 39.4+/-8.8 years. P/LP variants and VUS identified through previously reported whole-exome or whole genome sequencing were retained as separate evidential categories. The P/LP-associated gene set comprised 11 unique genes and the VUS associated set comprised 40 unique genes. Separate STRING functional-enrichment analyses evaluated Gene Ontology Biological Process, Molecular Function and Cellular Component terms, KEGG pathways, WikiPathways and STRING local network clusters. Terms meeting a Benjamini Hochberg false discovery rate threshold of <0.05 were organized into eight non-mutually-exclusive ontology/pathway categories. Gene to pathway mappings were subsequently projected to individual participants to estimate pathway representation and examine clinical associations. At least one reportable P/LP variant or VUS was identified in 336/668 participants (50.3%): 35 had a P/LP variant alone, 282 had VUS alone and 19 had a P/LP variant together with VUS in one or more additional genes. The most frequently represented categories were mitochondrial organization (247/336, 73.5%), autophagy related processes (228/336, 67.9%) and regulation of synaptic vesicle transport (201/336, 59.8%). PRKN was the most frequent P/LP-associated gene, occurring in 29/54 P/LP carriers, followed by PLA2G6 and PINK1. Lysosomal transport was represented exclusively by VUS-associated genes, particularly GBA1, VPS13C and LRRK2. Among P/LP carriers, additional VUS in distinct genes were not associated with age at onset (P = 0.81) or family history (52.6% versus 31.4%; P = 0.15). No pathway phenotype association remained significant after correction for multiple testing. Genetic findings in this Indian cohort converged across an interconnected mitochondrial autophagic lysosomal vesicular network, with different contributions from P/LP-associated and VUS associated gene sets. This study provides the first pathway resolved South Asian genetic profile and a framework for comparative studies across populations.

Pathogenic variants in leucine-rich repeat kinase 2 (LRRK2) 1 are among the most frequent monogenic causes of Parkinson's disease (PD) and act through a gain-of-function mechanism of increased kinase activity. LRRK2-targeted therapies are in clinical development, but interpretation of the rapidly expanding catalogue of rare LRRK2 variants remains a barrier to translation. Here, we present functionally annotated data on more than 350 LRRK2 variants using a standardized cellular assay with Rab10 phosphorylation as a readout of kinase activity and integrated these data with curated genetic and clinical annotations from the Movement Disorders Society Genetic Mutation Database (MDSGene). Variants differed in activation magnitude, ranging from modest increases (e.g., p.G2019S) to strongly activating substitutions such as p.Y1699C or p.L1795F. Activating variants occurred across the full length of LRRK2, although the largest effects clustered within the ROC-COR regulatory hub, where structural analysis identified subdomains forming an allosteric scaffold controlling kinase output. All known/established pathogenic variants showed increased activity, whereas benign and likely benign variants remained within the wild-type range. Functional effect sizes correlated with pathway activation in patient-derived immune cells, altogether providing a framework for ACMG-based variant interpretation in which kinase activation can support PS3 functional evidence for reclassification of variants.

Introduction: GCH1 has been implicated in Parkinson's disease (PD), but its risks variants and associations are not well defined. Objectives: To investigate the clinical relevance and PD risk associated with the GCH1 p.Ser80Asn variant. Methods: We first identified a segregating GCH1 p.Ser80Asn variant in a Malaysian Chinese PD family via whole genome sequencing (WGS). We assessed its risk association using multi-ancestry WGS data from the Global Parkinson's Genetics Program (GP2) (n=22,372PD vs n=8,826Controls) and meta-analysis of East Asian (EAS) cohorts (n=4,712PD vs 38,733Controls). Clinico-demographic details of affected variant carriers were collated. Results: The GCH1 p.Ser80Asn variant was enriched in GP2 EAS PD populations (n=9/2,757; 0.33%) but not detected in other ancestries. Meta-analysis revealed increased PD risk in EAS populations (odds ratio:5.1; 95%CI:2.3-10.7; p=2.89x10-5). Affected carriers (mean age at onset:56.3+-12.5 years) had additional occurrence of dystonia, while dementia was rare. Conclusions: The GCH1 p.Ser80Asn variant is a rare, EAS-enriched risk variant for PD.