Movement Disorders

Background: Pathogenic variants in GCH1 have been associated with Parkinson's disease (PD), but the clinical phenotype and longitudinal disease course of GCH1-associated PD remain incompletely characterized. Objectives: To characterize the genetic spectrum, clinical phenotype, and longitudinal progression of GCH1-associated PD across multiple populations. Methods: Whole-genome sequencing (WGS) and clinical exome sequencing (CES) data from the Global Parkinson Genetics Program (GP2) were analyzed together with unpublished and published GCH1-associated PD patients. Variant pathogenicity was classified according to ACMG criteria. Demographic, clinical, and longitudinal features were compared between GCH1 P/LP variant carriers and non-carrier PD patients; individuals with known pathogenic variants in PD-associated genes were excluded from both groups. Results: In the GP2 cohort (PD, n=22,825; controls, n=4,453), 16 pathogenic or likely pathogenic (P/LP) GCH1 variants were identified in 58 individuals, including 54 PD patients, one control, and three individuals with other neurodegenerative phenotypes (two with progressive supranuclear palsy and one with dementia with Lewy bodies). In the pooled-ancestry WGS analysis, GCH1 P/LP variants were enriched in PD patients versus controls (0.267% vs 0.023%; OR=11.854; 95% CI=1.620-86.699; p=0.0006). Variant frequencies in PD patients ranged from 0.121% to 0.714% across ancestries. In the CES cohort, P/LP variants were identified in 0.201% of PD patients. After integrating GP2 with additional unpublished and published datasets, 119 GCH1-associated PD patients were analyzed. Compared with noncarriers, carriers of P/LP GCH1 variants had an earlier age at onset (mean [SD], 53.7 [14.8] vs 59.2 [11.7] years; P < .001), lower levodopa equivalent daily dose requirements (mean [SD , 467.5 [331.7] vs 680.3 [466.4] mg/d; P < .001), and a higher frequency of a family history of Parkinson disease (47.6% vs 19.9%; P < .001). Adjusted Cox models showed significant delayed progression to motor fluctuations (HR=0.32, 95% CI=0.16-0.62) and levodopa-induced dyskinesias (HR=0.51, 95% CI=0.30-0.87). Conclusion: GCH1 pathogenic variants were associated with a clinically distinct phenotype characterized by earlier disease onset and slower progression of motor complications. These findings suggest that GCH1 genetic variants may serve as genetic biomarkers for patient stratification and prognosis in PD.

BackgroundThe relationship between essential tremor (ET) and Parkinsons disease (PD) remains controversial. Beyond viewing ET as a discrete risk factor for PD, recent frameworks propose that an ET phenotype may represent a clinical presentation of prodromal PD (pPD), consistent with the current reconceptualization of ET as a syndrome. Whether co-occurring subtle motor signs alter pPD probability in ET remains unknown. MethodsUsing the MDS research criteria, we calculated pPD probability in a large cohort of ET patients with and without subtle motor signs (rest tremor, hypomimia, isolated rigidity, reduced arm swing, altered repetitive movements, global slowing). Multivariable regression was used to identify independent predictors of pPD probability. ResultsAmong 599 ET patients (median disease duration: 12 years), only 6 (1.0%) met criteria for probable pPD. Although ET patients with subtle motor signs exhibited higher continuous pPD probability scores than those without, the frequency of possible or probable pPD did not differ significantly between groups. In multivariable regression, neither ET nor individual subtle motor signs, but hypomimia, were independent predictors of pPD probability, which was primarily driven by older age and male sex. ConclusionsLong-standing ET, whether isolated or accompanied by subtle motor signs, is not associated with pPD, with the possible exception of co-occurring hypomimia.

Background and Objectives: To test whether the positive correlation between rest tremor (RT) and ipsilateral striatal DAT binding reflects a tremor-specific ipsilateral mechanism or simply the globally better-preserved dopamine terminals in RT patients. Methods: We compared ipsilateral and contralateral correlations between striatal binding, rest tremor, bradykinesia and rigidity in two cross-sectional Parkinson disease cohorts from the Parkinson's Progression Markers Initiative (baseline, N=1055; follow-up, median 2.2 years, N=652). We tested whether correlations survived permutation testing that shuffled severity scores isolating severity-dependent effects from group-level effects and used out-of-sample prediction to compare how well binding predicted symptom presence versus severity. Results: Bradykinesia and rigidity showed large contralateral correlations, distinguishable from the permutation null in every comparison, and predicted both presence and severity. Rest tremor's ipsilateral correlation was not distinguishable from the null in most comparisons. Striatal binding, both ipsi or contralateral, predicted its presence (AUC 0.55-0.61) but not its severity (R2<0.002), in both cohorts. Conclusions: Our findings argue against a direct pathophysiologic link between tremor amplitude and ipsilateral dopaminergic function. More parsimoniously, the ipsilateral binding-RT correlation likely reflects a distinct degeneration pattern in patients with RT rather than a graded, dose-dependent circuit mechanism.

The genetics of Parkinsons disease (PD) in underrepresented populations remain poorly characterized, potentially overlooking population-specific contributions. We analyzed 461 Chilean PD cases from a movement disorders center. Pathogenic, likely pathogenic, or GBA1 risk variants were identified in 58 individuals (12.6%), mainly in LRRK2 (50%) and GBA1 (44.8%), while PRKN, SNCA, and SQSTM1 collectively represented 5.2%. All LRRK2 variants were p.G2019S, with an overall frequency of 6.3%, the highest reported in South America, and enrichment of Ashkenazi Jewish ancestry at this locus. These findings characterize the genetic landscape of PD in Chile and support its relevance for LRRK2-targeted studies.

Background: Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic risk factor for Parkinson's disease (PD). G2019S, the most common pathogenic variant, has been linked to milder motor symptoms, but the effects of other LRRK2 variants on disease trajectory remain incompletely characterized. R1441G, the second most common pathogenic variant, co-occurs with the PD risk variant M1646T on a shared haplotype. Whether this haplotype confers a distinct rate of motor progression has not been established. Methods: We analyzed up to 12 years of longitudinal data from 603 participants in the Parkinson's Progression Markers Initiative (PPMI) with PD and available whole-genome sequencing data: 394 sporadic PD, 169 G2019S carriers, 20 R1441G+M1646T carriers, and 20 M1646T carriers. Motor symptom progression (MDS-UPDRS III) was assessed using linear mixed-effects models with genotype-by-time interactions, adjusted for age at onset, disease duration at baseline, sex, race, baseline score, and levodopa equivalent daily dose. Results: R1441G+M1646T carriers exhibited 76% slower progression in OFF-state MDS-UPDRS III than sporadic PD (0.50 vs. 2.04 points/year; {beta}=-1.54 [95% CI: -2.48, -0.60]; p=0.001). G2019S carriers exhibited 26% slower progression (1.52 points/year; {beta}=-0.52 [-0.99, -0.06]; p=0.03). M1646T carriers did not differ from sporadic PD (p=0.60). Slower progression in R1441G+M1646T carriers was characterized by attenuated bradykinesia (64% slower; p=0.008), axial decline (76% slower; p=0.002), and a lack of orofacial symptom progression (p<0.001). R1441G+M1646T carriers also exhibited 55% slower self-reported motor decline (MDS-UPDRS II; p=0.04) Conclusions: R1441G+M1646T carriers exhibit substantially slower motor progression than sporadic PD while M1646T carriers do not.

Background An X-linked levodopa-responsive parkinsonism-epilepsy syndrome has been associated with PGK1, and the gene lies within the previously suspected PD locus PARK12. Objective To examine the association of common and rare PGK1 variants with PD. Methods We analyzed common and rare variants from Accelerated Medicines Partnership - Parkinsons Disease (AMP-PD) and UK Biobank (UKBB, total N=4,523 PD cases, 19,736 proxy cases, and 390,532 controls). To account for the X-linked location of PGK1, we used sex-stratified, combined regression models and optimized sequence Kernel association (SKAT-O) tests, followed by meta-analysis using MetaSKAT. Results We found no association between common or rare PGK1 variants and PD in sex-stratified or combined analyses, including after cross-cohort meta-analysis. Conclusion Although we did not find evidence supporting an association between PGK1 and PD, very rare pathogenic PGK1 variants may still contribute to syndromic parkinsonism. Future research could explore larger datasets to further examine this potential association.

Isolated rapid eye movement sleep behavior disorder (iRBD) is characterized by nigro-striatal deficits, comprising dopaminergic denervation of the striatum and loss of dopaminergic cells in the substantia nigra (SN), that may herald phenoconversion to clinically manifest synucleinopathy. While phenoconversion has repeatedly been shown to relate to pre-synaptic dopaminergic deficits in the striatum, potential involvement of loss of dopaminergic cells in the SN remain unclear. In addition, phenoconversion may independently relate to noradrenergic deficits, stemming from cell loss in the locus coeruleus/subcoeruleus (LC/LsC) complex. Fifty-six iRBD patients were included and clinically followed over an 11-years as part of the ICEBERG study. Putamen dopamine denervation was quantified using 123I-FP-CIT single-photon emission computed tomography. Cell loss in the SN and LC/LsC was quantified using neuromelanin-sensitive magnetic resonance imaging (MRI). SN cell loss was additionally characterized as free water, derived from diffusion-weighted MRI. The primary outcome was time to phenoconversion. Cox proportional hazards regression was used to investigate relationships between phenoconversion risk and imaging predictors, estimated as hazard ratios (HRs). Out of 56 patients, 24 (41%) converted to a clinically manifest synucleinopathy [PD=14 (58%), DLB=8 (33%), MSA=2 (8%)] over a maximum period of 11 years. We replicated the well-established finding that reduced putamen DaT confers an increased phenoconversion risk [HR (95%CI)=3.1 (1.7-5.5), P<0.001]. We extend on this by showing a similar relationship for SN neuromelanin [HR (95%CI)=2.5 [1.3-4.6], P=0.004], SN free water [HR (95%CI)=1.54 (1.06-2.24), P=0.025], and LC/LsC neuromelanin [HR (95%CI)=2.1 (1.2-3.7), P=0.011], demonstrating involvement of the broader nigro-striatal dopaminergic system along with potential involvement of noradrenergic neurotransmission. When adjusting for putamen DaT, the relationship between phenoconversion risk and SN neuromelanin was attenuated [P=0.16], suggesting partial overlap between the metrics. In contrast, when modelled together, SN neuromelanin [HR (95%CI)=2.8 (1.4-5.6), P=0.003] and LC/LsC neuromelanin [HR (95%CI)=2.3 (1.1-4.8), P=0.037] contributed to phenoconversion risk independently of each other, indicating a differential contribution of dopaminergic and noradrenergic neurotransmitter deficits to iRBD phenoconversion. We demonstrate that phenoconversion in iRBD relates similarly to dopaminergic denervation of the putamen and cell loss in the SN. This opens possibilities for using NM-MRI, which can simultaneously capture dopaminergic and noradrenergic deficits, as an alternative to nuclear imaging techniques when estimating phenoconversion risk in iRBD.

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.

Background. The VPS35 p.D620N variant causes autosomal dominant Parkinson's disease (PD) and has been shown to activate the LRRK2 kinase pathway, resulting in increased Rab substrate phosphorylation in peripheral immune cells and elevated urinary bis(monoacylglycero)phosphate (BMP) levels. Recently, a VPS35 variant of unknown significance (c.959C>T; p.A320V) was described in two late-onset sporadic PD patients. Methods. We ascertained a family from the Canary Islands in which six siblings were chronically exposed to high doses of pesticides. Three siblings developed levodopa-responsive, akinetic-rigid PD, while the other three remained unaffected. Whole-exome sequencing was performed in the three affected siblings. The frequency of the resulting candidate variant was assessed in 23,327 PD patients and 9,235 controls from four independent cohorts. Members of this pedigree and unrelated controls were assessed for LRRK2 kinase activity in monocytes and neutrophils and BMP levels in urine. Results. The three affected siblings were all heterozygous for p.A320V, whereas the three unaffected siblings did not carry the variant. In the combined PD case-control cohort, p.A320V was identified in six patients and one control. However, unlike p.D620N, heterozygous carrier status for p.A320V was not associated with increased LRRK2 kinase activity or elevated urine BMP levels. Conclusions. While VPS35 p.A320V co-segregated with PD in this family, it did not exhibit the characteristic LRRK2-associated biomarker signature observed in VPS35 p.D620N carriers. It is possible that p.A320V exerts a subtle effect on VPS35 function that was not captured by the assays performed and that chronic pesticide exposure contributed to disease penetrance in this pedigree.

Transcranial alternating current stimulation (tACS) is a promising noninvasive intervention for modulating pathological brain oscillations in Parkinson's disease (PD). To evaluate its clinical and neurophysiological efficacy, we searched five databases (Web of Science, PubMed, Scopus, Google Scholar and APA PsycInfo) up to August 31, 2025, for trials employing tACS in patients with idiopathic PD. Risk of bias was assessed using the RoB 2 and ROBINS-I tools. Random-effects meta-analyses were used to calculate standardized (SMD) and unstandardized mean differences (MD) with 95% confidence intervals (CIs). We included 10 studies (184 patients with PD, mean age: 64.9, mean disease duration: 5.2 years) in the qualitative review and seven trials (146 patients with PD, mean age: 65.6, mean disease duration: 5 years) in the meta-analysis. No statistically significant differences favoring active tACS over control were found in overall motor severity (UPDRS: SMD = 0.21, 95% CI [-0.10, 0.52], p = 0.097), tremor (SMD = -0.40, 95% CI [-1.97, 1.17], p = 0.478), or a neurophysiological marker of inhibitory response, represented by short intracortical inhibition (MD = 0.00, 95% CI [-0.40, 0.41], p = 0.971). The prediction intervals indicated substantial uncertainty, and significant between-study heterogeneity was observed, particularly for tremor outcomes (I2 = 86.1%). This variability and limitation in evidence quality is largely driven by small sample sizes, highly heterogeneous stimulation protocols, and varying outcome assessments. Systematically, tACS was generally well-tolerated, with no serious adverse events reported across the included studies; however, formal safety assessment was beyond the scope of this review. Current exploratory evidence shows a lack of consistent improvements in motor symptoms or functions in PD largely due to protocol-level heterogeneity. Future studies should consistently assess the MDS-UPDRS III post-tACS and report its specific subscores alongside neurophysiological measures to enable robust meta-analyses.

Parkinson disease (PD) is characterized by excessive neural synchronization in the 13 to 30 Hz beta band within basal ganglia circuits. Conventional therapies, including dopaminergic medication and deep brain stimulation (DBS), reduce beta synchrony while enhancing lower-frequency theta activity. As an adjunct to these treatments, music and auditory rhythms improve motor function in PD, but the neural mechanisms remain unclear. Here, we recorded local field potentials in the subthalamic nucleus (STN) of patients with PD in the medication off state to test how structured musical elements shape subcortical synchrony. Spectral and neural state-space analyses showed that rhythmic and harmonic components of music produced effects comparable to dopaminergic therapy, suppressing beta-band oscillations while enhancing theta band activity. These effects were strong in the dorsal sensorimotor STN, whereas the ventral limbic STN showed minor modulation. Directional connectivity analysis further revealed that music-induced beta and theta changes were accompanied by increased cortex to STN drive, consistent with top down recruitment of the cortical subthalamic hyperdirect pathway. Notably, harmonic consonance produced network-level modulation comparable to, and in some cases greater than, rhythmic entrainment, extending beyond the established framework of beat based basal ganglia engagement. Together, these findings identify frequency selective, region specific, and stimulus-locked mechanisms by which music reshapes pathological basal ganglia activity in PD, providing direct electrophysiological evidence that auditory stimulation can transiently shift subcortical dynamics toward a medication like state.

Blood-based (BB) biomarker investigations in Parkinson disease (PD) and in mild traumatic brain injury (mTBI) have substantially grown over the past decade. High risks for PD in young post-mTBI veterans have been inferred from medical record data using actuarial modeling. However, potential utility of BB biomarkers to quantify risks vs. no risk for PD in young post-mTBI veterans has not been established. Previously we reported post-mTBI veterans performed significantly below the standardized normative scores for their age and education level on specific domains of executive functioning, on par with senior aged individuals with early-stage PD. Here, we examined serum brain-derived neurotropic factor (BDNF), ubiquitin C-terminal hydrolase-L1 (UCH-L1), glial fibrillary acidic protein (GFAP), and S100 calcium-binding protein {beta} (S100B) in association with executive functioning outcomes in search of a bio-cognitive model suitable to differentiate risk from no risk for prodromal PD. A reference range of bio-cognitive cut-points were derived from Area Under the Curve (AUC) sensitivity and specificity methods. Our data revealed two bio-cognitive signatures with reference range cut-points when GFAP was paired with cognitive flexibility / attention scores, and when S100B was paired with categorical / semantic verbal memory scores. Both bio-cognitive signatures revealed prodromal PD risk vs.no-risk parameters that remained relevant for differentiating young veterans who had encountered a past mTBI and those who had not experienced a mTBI. Subjects with early-stage PD who had withstood a mTBI up to 10- to 40-years earlier were also differentiated from those who had no mTBI history. These results indicate the predictive utility of expanding the biomarker field to include reference ranges, cut-points, and specific cognitive domains to estimate risks for PD in a clinic setting. These preliminary data also add value in establishing a quantifiable bio-cognitive risk signature to identify prodromal PD risks in young adults prior to obvious cognitive and motor decline. While encouraging, these data require further follow-up with a larger sample size in a longitudinal design to validate these findings.

Objective and scalable approaches for detecting subtle motor impairment in isolated REM sleep behavior disorder (iRBD), a prodromal stage of Parkinson's disease, remain limited. We investigated whether markerless motion capture from single RGB-camera videos can identify gait abnormalities in people living with iRBD and provide interpretable digital biomarkers. We retrospectively analyzed 93 standardized walking videos from three clinical sites. Human pose estimation extracted 12 body markers and 14 kinematic time series. Thirty-five machine learning approaches classified healthy controls (HC) and people with iRBD. The Movement Disorder Society Unified Parkinson's Disease Rating Scale Part 3 (MDS-UPDRS III) served as the clinical baseline. The best-performing model (tsfresh+XGBoost) achieved an AUROC of 0.739, significantly outperforming the MDS-UPDRS III sum score when trained on data from all three sites. Harmonized multi-site training improved performance. SHAP identified hip-related temporal features as key contributors, which differed between groups and showed stronger associations with regional dopaminergic deficits than clinical scores. Single-camera gait analysis may provide scalable digital biomarkers for low-cost screening and monitoring of prodromal PD.

Despite major progress in genomic risk loci identification, biological mechanisms underlying Parkinson's disease (PD) remain incompletely understood and the informativity of polygenic score (PGS)-based prediction remains modest. Polytranscriptomic scores (PTS) - the sum of an individual's observed gene expression weighted by transcriptome-wide association z-scores - combine the stability of genetics with the dynamic biology of gene expression and have the potential to identify associations not captured by genetics alone. We present the first large-scale cross-trait and multi-PTS analysis of PD, calculating ~550 PTS for 100 phenotypes using whole-blood RNA-seq data from three independent clinical cohorts in the Accelerating Medicines Partnership Parkinson's Disease programme (AMP-PD) (N = 2,741; NCASES = 1,644). We identify 26 Bonferroni significant cross-trait PTS associations with PD (p<9x10-5) involving 18 phenotypes and 11 trait categories, including neurodegenerative diseases, respiratory function, sleep and cardiovascular traits. Only one of these associations was observed using corresponding PGS, highlighting the added value of integrating directly measured transcriptomic data. Combining multiple PTS within machine learning multi-PTS models improved prediction of PD case/control status beyond age, sex and PD-PGS in external validation, with a sparse model including an additional seven PTS achieving an AUC of 0.74 [0.70-0.78], representing a 0.09-point improvement. These findings reveal transcriptomic overlap between PD and a range of clinically relevant traits, providing novel insights into disease biology with potential to improve disease prediction.

Background: Levodopa is time-critical in hospitalized Parkinson disease. Whether dosing fidelity depends on care setting or documented access status is unclear. Objectives: To quantify levodopa dosing fidelity, test ICU exposure with clustering-aware methods, and test whether documented access type is associated with delayed or omitted dosing. Methods: Retrospective cohort study using MIMIC-IV (2011-2022). Adults with Parkinson disease and [&ge;]1 scheduled levodopa dose contributed 1,665 admissions and 39,322 doses. ICU exposure was tested with a patient-clustered GEE model. Among ICU-exposed doses, access type (normal, tube feeding, parenteral nutrition, NPO) was modeled in one fully adjusted model and tested for specificity, restricted to the ICU, against an active-comparator medication (statins). Results: Of 39,322 doses, 79.8% were on time by the primary 60-minute definition; a symmetric {+/-}15-minute definition classified 68.8% as mistimed. ICU exposure was not associated with delayed or omitted dosing after clustering (patient-clustered OR, 0.87; 95% CI, 0.74-1.01). Among ICU-exposed doses, NPO was associated with delayed or omitted dosing (adjusted OR, 1.89; 95% CI, 1.36-2.62) and tube feeding with lower odds (adjusted OR, 0.62; 95% CI, 0.42-0.92; P < .001). The comparator medication showed a directionally consistent but inconclusive interaction (OR, 1.27-1.28; 92 patients). A route-order association was not observed among immediate-release formulations (OR, 0.72; 4 patients). Conclusions: ICU admission alone was not associated with dosing unreliability after clustering. Among ICU-exposed doses, access type, not a single pooled category, was associated with dosing reliability; a comparator-medication check, valid only in the ICU, was directionally consistent but inconclusive.

Dopamine replacement therapy (DRT) alleviates motor symptoms in Parkinson's disease (PD) but can trigger hallucinations in a subset of patients, yet the neural basis of this selective vulnerability is unknown. Hallucinations are among the most disabling non-motor symptoms of PD, linked to social isolation, dementia and institutionalization. Using a validated robotic paradigm to induce and quantify hallucinations in real-time, combined with resting-state fMRI in a crossover On/Off DRT design, we studied patients with PD with (PD-H) and without (PD-nH) hallucinations. DRT selectively amplified sensitivity to robot-induced hallucinations in patients with pre-existing hallucinatory phenotype (PD-H, but not PD-nH) and was accompanied by cortico-striatal and large-scale network hyperconnectivity. Rather than supporting a uniform hallucinogenic effect of dopamine in PD, these findings indicate that DRT interacts with an intrinsic neural vulnerability that varies in patients. Prospective studies will establish whether this pharmacological-behavioural signature identifies patients at risk before clinical hallucinations emerge.

Parkinson disease (PD) affects more than 1.1 million individuals in the United States and around 12 million worldwide. Although Genome Wide Association Studies (GWAS) have substantially advanced our understanding of PD genetic architecture, the regulatory mechanisms linking PD risk loci to disease-relevant gene expression remain incompletely characterized, limiting our ability to infer disease mechanisms from genetic associations. Here, we integrated disease-state parietal cortex transcriptomics with the International Parkinsons Disease Genomics Consortium (iPDGC) locus prioritization to refine PD gene nomination and identify biologically plausible candidates missed by GWAS-only approaches. Using bulk RNA-seq from 99 neuropathologically confirmed PD cases and 30 neuropathologically confirmed controls, we prioritized candidate genes across 78 loci and classified them according to concordance between genetic evidence and differential expression in diseased cortices. This integrative approach recovered candidate genes not captured by external GWAS-based prioritization methods and highlighted synaptic, lysosomal, and proteostasis pathways as major components of PD risk biology. Network and transcription factor analyses further suggested coordinated regulation of these genes, with STAT3 emerging as a putative upstream glial regulator. Together, these findings suggest that integrating disease-state transcriptomics with genetic prioritization can refine PD risk-gene nomination and uncover regulatory programs that may be missed by GWAS alone.

Tandem repeat expansions (TREs) cause over 50 neurological conditions, yet their contribution to neurodegenerative disease risk at a population scale remains incompletely characterized. We performed a TRE association study across 6,539 short tandem repeat loci in 276,411 individuals from the UK Biobank and 44,370 individuals from the All of Us Research Program, using two composite neurodegenerative phenotypes to increase statistical power and capture pleiotropic effects. Meta-analysis across the two cohorts identified associations at eight established pathogenic TRE loci, including C9orf72, DMPK, HTT, ATXN2, ATXN3, CACNA1A, CNBP, and PPP2R2B, recovering known disease-associated expansions from short-read sequencing data at biobank scale. We also identified candidate associations at three additional loci. An intronic AATAA expansion in DAPK1 reached significance (q = 0.0045), with fine-mapping and conditional analysis supporting the repeat as the likely variant underlying the association. An intronic ATTTT expansion in ANK3 (q = 0.034) was observed exclusively in individuals of African and Latino/admixed American ancestry, underscoring the importance of ancestrally diverse cohorts for genetic discovery. An exonic polyalanine expansion in RPL14 was also significant (q = 0.039), where longer alleles were consistently associated with reduced RPL14 expression across independent datasets. Together, these findings identify candidate risk loci for neurodegenerative disease that may expand the contribution of TREs to neurodegenerative disease beyond known repeat expansion disorders.

The Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS) is the global standard for characterising Parkinson's Disease (PD) in clinical contexts. However, the specific symptom phenotypes it captures remain poorly understood, potentially limiting its value for diagnosis, prognosis, and stratifying patients. To address this, we developed a spectral estimation approach to find the unique latent variables captured by the 60 scores of MDS-UPDRS parts I, II, and III from 852 sporadic PD patients. Our analysis revealed six latent variables that robustly captured variation between patients and generalised across cohorts. The primary variable encoded symptom laterality, while others encoded distinct clinical features including tremor severity, and revealed an unexpected dissociation between patient self-reported symptoms and clinician-assessed symptoms, highlighting potential gaps in how PD is currently evaluated and understood. Our findings open the door to precise MDS-UPDRS phenotyping of patients for treatments and clinical trials.

Isolated REM sleep behaviour disorder (RBD) is the strongest prodromal marker of Parkinson's disease (PD) and dementia with Lewy bodies, yet diagnosis requires video-polysomnography with assisted montage and expert scoring and does not scale to screening or trial enrichment. We developed a fully automated, self-applied system that detects RBD from a pair of electrodes placed behind the ears, with no manual scoring at any stage. A novel bipolar mastoid ExG derivation enables both sleep staging and quantification of REM sleep without atonia (RWA). A fine-tuned deep-learning 1-channel model staged sleep at a Cohen's kappa of 0.65 in PD, iRBD and controls ({kappa} = 0.73 for the 2-channel model). Automated mastoid RWA correlated strongly with expert chin SINBAR scoring (r = 0.82). In self-applied home recordings from 76 participants, the 1-channel system detected RBD with an AUC of 0.95 (sensitivity 94%, specificity 86%), reproduced on in-lab polysomnographies (AUC 0.93, n = 378). In RBD, between-night RWA variability warrants repeated nights for prognostic monitoring. The system provides a scalable tool for RBD detection and a continuous RWA measure for longitudinal studies of neurodegeneration.