Pleiotropy with sex-specific traits reveals genetic aspects of sex differences in Parkinson's disease

Parkinson's disease is an age-related neurodegenerative disorder with a higher incidence in males than females. The causes for this sex difference are unknown. Genome-wide association studies (GWAS) have identified 90 Parkinson's disease risk loci, but the genetic studies have not found sex-specific differences in allele frequency on autosomal chromosomes or sex chromosomes. Genetic variants, however, could exert sex-specific effects on gene function and regulation of gene expression. To identify genetic loci that might have sex-specific effects, we studied pleiotropy between Parkinson's disease and sex-specific traits. Summary statistics from GWASs were acquired from large-scale consortia for Parkinson's disease (n cases = 13 708; n controls = 95 282), age at menarche (n = 368 888 females) and age at menopause (n = 69 360 females). We applied the conditional/conjunctional false discovery rate (FDR) method to identify shared loci between Parkinson's disease and these sex-specific traits. Next, we investigated sex-specific gene expression differences in the superior frontal cortex of both neuropathologically healthy individuals and Parkinson's disease patients (n cases = 61; n controls = 23). To provide biological insights to the genetic pleiotropy, we performed sex-specific expression quantitative trait locus (eQTL) analysis and sex-specific age-related differential expression analysis for genes mapped to Parkinson's disease risk loci. Through conditional/conjunctional FDR analysis we found 11 loci shared between Parkinson's disease and the sex-specific traits age at menarche and age at menopause. Gene-set and pathway analysis of the genes mapped to these loci highlighted the importance of the immune response in determining an increased disease incidence in the male population. Moreover, we highlighted a total of nine genes whose expression or age-related expression in the human brain is influenced by genetic variants in a sex-specific manner. With these analyses we demonstrated that the lack of clear sex-specific differences in allele frequencies for Parkinson's disease loci does not exclude a genetic contribution to differences in disease incidence. Moreover, further studies are needed to elucidate the role that the candidate genes identified here could have in determining a higher incidence of Parkinson's disease in the male population.

Lysosomal Polygenic Burden Drives Cognitive Decline in Parkinson's Disease with Low Alzheimer Risk

BACKGROUND

Genetics influence cognitive progression in Parkinson's disease, possibly through mechanisms related to Lewy and Alzheimer's disease pathology. Lysosomal polygenic burden has recently been linked to more severe Lewy pathology post mortem.

OBJECTIVES

To assess the influence of lysosomal polygenic burden on cognitive progression in Parkinson's disease patients with low Alzheimer's disease risk.

METHODS

Using Cox regression we assessed association between lysosomal polygenic scores and time to Montreal Cognitive Assessment score ≤ 21 in the Parkinson's Progression Markers Initiative cohort (n = 374), with replication in data from the Parkinson's Disease Biomarker Program (n = 777). Patients were stratified by Alzheimer's disease polygenic risk.

RESULTS

The lysosomal polygenic score was associated with faster progression of cognitive decline in patients with low Alzheimer's disease risk in both datasets (P = 0.0032 and P = 0.0054, respectively).

CONCLUSION

Our study supports complex interplay between genetics and neuropathology in Parkinson's disease-related cognitive impairment, emphasizing the role of lysosomal polygenic burden. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Dopamine agonist serum concentrations and impulse control disorders in Parkinson's disease

BACKGROUND AND PURPOSE

Impulse control disorders (ICDs) are common among Parkinson's disease patients using dopamine agonists. We wanted to determine whether ICD patients have higher dopamine agonist serum concentrations than those without any sign of ICD.

METHODS

Patients who used either pramipexole or ropinirole depot once daily were screened for ICDs using the validated Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale. Those who scored above the cut-off for one or more of the four defined ICDs (gambling, compulsive sexual behavior, compulsive shopping, and binge-eating) were compared in a case-control study to patients who scored zero points (no evidence of ICD) on the same items. They were examined clinically and evaluated using relevant scales. Three blood samples were taken on the same day: before daily dose, and then 6 and 12 h later.

RESULTS

Forty-six patients were included: 19 ICD-positive and 27 controls. Ropinirole serum concentrations 6 h after daily intake (Cmax ) were higher in the case group compared to the control group, as was the daily ropinirole dosage. No differences were observed in serum concentrations, dosage or total drug exposure for pramipexole. Disease duration and length of dopamine agonist treatment was significantly longer among ICD patients for ropinirole, but not for pramipexole.

CONCLUSIONS

The use of pramipexole may in itself confer high ICD risk, whereas ICDs among ropinirole users depend more on serum concentration and drug exposure. The pharmacokinetic properties of ropinirole make it challenging to predict its effects on patients, which supports the need for therapeutic drug monitoring to reduce risk of ICD.

Intelligent digital tools for screening of brain connectivity and dementia risk estimation in people affected by mild cognitive impairment: the AI-Mind clinical study protocol

More than 10 million Europeans show signs of mild cognitive impairment (MCI), a transitional stage between normal brain aging and dementia stage memory disorder. The path MCI takes can be divergent; while some maintain stability or even revert to cognitive norms, alarmingly, up to half of the cases progress to dementia within 5 years. Current diagnostic practice lacks the necessary screening tools to identify those at risk of progression. The European patient experience often involves a long journey from the initial signs of MCI to the eventual diagnosis of dementia. The trajectory is far from ideal. Here, we introduce the AI-Mind project, a pioneering initiative with an innovative approach to early risk assessment through the implementation of advanced artificial intelligence (AI) on multimodal data. The cutting-edge AI-based tools developed in the project aim not only to accelerate the diagnostic process but also to deliver highly accurate predictions regarding an individual's risk of developing dementia when prevention and intervention may still be possible. AI-Mind is a European Research and Innovation Action (RIA H2020-SC1-BHC-06-2020, No. 964220) financed between 2021 and 2026. First, the AI-Mind Connector identifies dysfunctional brain networks based on high-density magneto- and electroencephalography (M/EEG) recordings. Second, the AI-Mind Predictor predicts dementia risk using data from the Connector, enriched with computerized cognitive tests, genetic and protein biomarkers, as well as sociodemographic and clinical variables. AI-Mind is integrated within a network of major European initiatives, including The Virtual Brain, The Virtual Epileptic Patient, and EBRAINS AISBL service for sensitive data, HealthDataCloud, where big patient data are generated for advancing digital and virtual twin technology development. AI-Mind's innovation lies not only in its early prediction of dementia risk, but it also enables a virtual laboratory scenario for hypothesis-driven personalized intervention research. This article introduces the background of the AI-Mind project and its clinical study protocol, setting the stage for future scientific contributions.

Epigenome-wide association study of peripheral immune cell populations in Parkinson's disease

Understanding the contribution of immune mechanisms to Parkinson's disease pathogenesis is an important challenge, potentially of major therapeutic implications. To further elucidate the involvement of peripheral immune cells, we studied epigenome-wide DNA methylation in isolated populations of CD14+ monocytes, CD19+ B cells, CD4+ T cells, and CD8+ T cells from Parkinson's disease patients and healthy control participants. We included 25 patients with a maximum five years of disease duration and 25 controls, and isolated four immune cell populations from each fresh blood sample. Epigenome-wide DNA methylation profiles were generated from 186 samples using the Illumina MethylationEpic array and association with disease status was tested using linear regression models. We identified six differentially methylated CpGs in CD14+ monocytes and one in CD8 + T cells. Four differentially methylated regions were identified in monocytes, including a region upstream of RAB32, a gene that has been linked to LRRK2. Methylation upstream of RAB32 correlated negatively with mRNA expression, and RAB32 expression was upregulated in Parkinson's disease both in our samples and in summary statistics from a previous study. Our epigenome-wide association study of early Parkinson's disease provides evidence for methylation changes across different peripheral immune cell types, highlighting monocytes and the RAB32 locus. The findings were predominantly cell-type-specific, demonstrating the value of isolating purified cell populations for genomic studies.

Lysosomal polygenic risk is associated with the severity of neuropathology in Lewy body disease

Intraneuronal accumulation of misfolded α-synuclein is the pathological hallmark of Parkinson's disease and dementia with Lewy bodies, often co-occurring with variable degrees of Alzheimer's disease related neuropathology. Genetic association studies have successfully identified common variants associated with disease risk and phenotypic traits in Lewy body disease, yet little is known about the genetic contribution to neuropathological heterogeneity. Using summary statistics from Parkinson's disease and Alzheimer's disease genome-wide association studies, we calculated polygenic risk scores and investigated the relationship with Lewy, amyloid-β and tau pathology. Associations were nominated in neuropathologically defined samples with Lewy body disease from the Netherlands Brain Bank (n = 217) and followed up in an independent sample series from the Mayo Clinic Brain Bank (n = 394). We also generated stratified polygenic risk scores based on single-nucleotide polymorphisms annotated to eight functional pathways or cell types previously implicated in Parkinson's disease and assessed for association with Lewy pathology in subgroups with and without significant Alzheimer's disease co-pathology. In an ordinal logistic regression model, the Alzheimer's disease polygenic risk score was associated with concomitant amyloid-β and tau pathology in both cohorts. Moreover, both cohorts showed a significant association between lysosomal pathway polygenic risk and Lewy pathology, which was more consistent than the association with a general Parkinson's disease risk score and specific to the subset of samples without significant concomitant Alzheimer's disease related neuropathology. Our findings provide proof of principle that the specific risk alleles a patient carries for Parkinson's and Alzheimer's disease also influence key aspects of the underlying neuropathology in Lewy body disease. The interrelations between genetic architecture and neuropathology are complex, as our results implicate lysosomal risk loci specifically in the subset of samples without Alzheimer's disease co-pathology. Our findings hold promise that genetic profiling may help predict the vulnerability to specific neuropathologies in Lewy body disease, with potential relevance for the further development of precision medicine in these disorders.

Prehospital screening of acute stroke with the National Institutes of Health Stroke Scale (ParaNASPP): a stepped-wedge, cluster-randomised controlled trial

BACKGROUND

Timely treatment of acute stroke depends on early identification and triage. Improved methods for recognition of stroke in the prehospital setting are needed. We aimed to assess whether use of the National Institutes of Health Stroke Scale (NIHSS) by paramedics in the ambulance could improve communication with the hospital, augment triage, and enhance diagnostic accuracy of acute stroke.

METHODS

The Paramedic Norwegian Acute Stroke Prehospital Project (ParaNASPP) was a stepped-wedge, single-blind, cluster-randomised controlled trial. Patients with suspected acute stroke, who were evaluated by paramedics from five ambulance stations in Oslo, Norway, were eligible for inclusion. The five ambulance stations (defined as clusters) all initially managed patients according to a standard stroke protocol (control group), with randomised sequential crossover of each station to the intervention group. The intervention consisted of supervised training on NIHSS scoring, a mobile application to aid scoring, and standardised communication with stroke physicians. Random allocation was done via a simple lottery draw by administrators at Oslo University Hospital, who were independent of the research team. Allocation concealment was not possible due to the nature of the intervention. The primary outcome was the positive predictive value (PPV) for prehospital identification of patients with a final discharge diagnosis of acute stroke, analysed by intention to treat. Prespecified secondary safety outcomes were median prehospital on-scene time and median door-to-needle time. This trial is registered with ClinicalTrials.gov, NCT04137874, and is completed.

FINDINGS

Between June 3, 2019, and July 1, 2021, 935 patients were evaluated by paramedics for suspected acute stroke. 134 patients met exclusion criteria or did not consent to participate. The primary analysis included 447 patients in the intervention group and 354 in the control group. There was no difference in PPV for prehospital identification of patients with a final discharge diagnosis of acute stroke between the intervention group (48·1%, 95% CI 43·4-52·8) and control group (45·8%, 40·5-51·1), with an estimated percentage points difference between groups of 2·3 (95% CI -4·6 to 9·3; p=0·51). Median prehospital on-scene time increased by 5 min in the intervention group (29 min [IQR 23-36] vs 24 min [19-31]; p<0·0001), whereas median door-to-needle time was similar between groups (26 min [21-36] vs 27 min [20-36]; p=0·90). No prehospital deaths were reported in either group.

INTERPRETATION

The intervention did not improve diagnostic accuracy in patients with suspected stroke. A general increase in prehospital time during the pandemic and the identification of smaller strokes that require more deliberation are possible explanations for the increased on-scene time. The ParaNASPP model is to be implemented in Norway from 2023, and will provide real-life data for further research.

FUNDING

Norwegian Air Ambulance Foundation and Oslo University Hospital.

Transcriptomic profiling of Parkinson's disease brains reveals disease stage specific gene expression changes

Parkinson´s disease (PD) is a progressive neurodegenerative disorder characterized by both motor and non-motor symptoms. Aggravation of symptoms is mirrored by accumulation of protein aggregates mainly composed by alpha-synuclein in different brain regions, called Lewy bodies (LB). Previous studies have identified several molecular mechanisms as autophagy and inflammation playing a role in PD pathogenesis. Increased insights into mechanisms involved in early disease stages and driving the progression of the LB pathology are required for the development of disease-modifying strategies. Here, we aimed to elucidate disease stage-specific transcriptomic changes in brain tissue of well-characterized PD and control donors. We collected frontal cortex samples from 84 donors and sequenced both the coding and non-coding RNAs. We categorized our samples into groups based on their degree of LB pathology aiming to recapitulate a central aspect of disease progression. Using an analytical pipeline that corrected for sex, age at death, RNA quality, cell composition and unknown sources of variation, we found major disease stage-specific transcriptomic changes. Gene expression changes were most pronounced in donors at the disease stage when microscopic LB changes first occur in the sampled brain region. Additionally, we identified disease stage-specific enrichment of brain specific pathways and immune mechanisms. On the contrary, we showed that mitochondrial mechanisms are enriched throughout the disease course. Our data-driven approach also suggests a role for several poorly characterized lncRNAs in disease development and progression of PD. Finally, by combining genetic and epigenetic information, we highlighted two genes (MAP4K4 and PHYHIP) as candidate genes for future functional studies. Together our results indicate that transcriptomic dysregulation and associated functional changes are highly disease stage-specific, which has major implications for the study of neurodegenerative disorders.

Genetic Investigation of Consanguineous Pakistani Families Segregating Rare Spinocerebellar Disorders

Spinocerebellar disorders are a vast group of rare neurogenetic conditions, generally characterized by overlapping clinical symptoms including progressive cerebellar ataxia, spastic paraparesis, cognitive deficiencies, skeletal/muscular and ocular abnormalities. The objective of the present study is to identify the underlying genetic causes of the rare spinocerebellar disorders in the Pakistani population. Herein, nine consanguineous families presenting different spinocerebellar phenotypes have been investigated using whole exome sequencing. Sanger sequencing was performed for segregation analysis in all the available individuals of each family. The molecular analysis of these families identified six novel pathogenic/likely pathogenic variants; ZFYVE26: c.1093del, SACS: c.1201C>T, BICD2: c.2156A>T, ALS2: c.2171-3T>G, ALS2: c.3145T>A, and B4GALNT1: c.334_335dup, and three already reported pathogenic variants; FA2H: c.159_176del, APTX: c.689T>G, and SETX: c.5308_5311del. The clinical features of all patients in each family are concurrent with the already reported cases. Hence, the current study expands the mutation spectrum of rare spinocerebellar disorders and implies the usefulness of next-generation sequencing in combination with clinical investigation for better diagnosis of these overlapping phenotypes.

A homozygous founder variant in PDE2A causes paroxysmal dyskinesia with intellectual disability

Intellectual developmental disorder with paroxysmal dyskinesia or seizures (IDDPADS, OMIM#619150) is an ultra-rare childhood-onset autosomal recessive movement disorder manifesting paroxysmal dyskinesia, global developmental delay, impaired cognition, progressive psychomotor deterioration and/or drug-refractory seizures. We investigated three consanguineous Pakistani families with six affected individuals presenting overlapping phenotypes partially consistent with the reported characteristics of IDDPADS. Whole exome sequencing identified a novel missense variant in Phosphodiesterase 2A (PDE2A): NM_002599.4: c.1514T > C p.(Phe505Ser) that segregated with the disease status of individuals in these families. Retrospectively, we performed haplotype analysis that revealed a 3.16 Mb shared haplotype at 11q13.4 among three families suggesting a founder effect in this region. Moreover, we also observed abnormal mitochondrial morphology in patient fibroblasts compared to controls. Belonging to diverse age groups (13 years-60 years), patients presented paroxysmal dyskinesia, developmental delay, cognitive abnormalities, speech impairment, and drug-refractory seizures with variable onset of disease (as early as 3 months of age to 7 years). Together with the previous reports, we observed that intellectual disability, progressive psychomotor deterioration, and drug-refractory seizures are consistent outcomes of the disease. However, permanent choreodystonia showed variability. We also noticed that the later onset of paroxysmal dyskinesia manifests severe attacks in terms of duration. Being the first report from Pakistan, we add to the clinical and mutation spectrum of PDE2A-related recessive disease raising the total number of patients from six to 12 and variants from five to six. Together, with our findings, the role of PDE2A is strengthened in critical physio-neurological processes.

Investigation of Shared Genetic Risk Factors Between Parkinson's Disease and Cancers

BACKGROUND

Epidemiological studies that examined the association between Parkinson's disease (PD) and cancers led to inconsistent results, but they face a number of methodological difficulties.

OBJECTIVE

We used results from genome-wide association studies (GWASs) to study the genetic correlation between PD and different cancers to identify common genetic risk factors.

METHODS

We used individual data for participants of European ancestry from the Courage-PD (Comprehensive Unbiased Risk Factor Assessment for Genetics and Environment in Parkinson's Disease; PD, N = 16,519) and EPITHYR (differentiated thyroid cancer, N = 3527) consortia and summary statistics of GWASs from iPDGC (International Parkinson Disease Genomics Consortium; PD, N = 482,730), Melanoma Meta-Analysis Consortium (MMAC), Breast Cancer Association Consortium (breast cancer), the Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome (prostate cancer), International Lung Cancer Consortium (lung cancer), and Ovarian Cancer Association Consortium (ovarian cancer) (N comprised between 36,017 and 228,951 for cancer GWASs). We estimated the genetic correlation between PD and cancers using linkage disequilibrium score regression. We studied the association between PD and polymorphisms associated with cancers, and vice versa, using cross-phenotypes polygenic risk score (PRS) analyses.

RESULTS

We confirmed a previously reported positive genetic correlation of PD with melanoma (Gcorr = 0.16 [0.04; 0.28]) and reported an additional significant positive correlation of PD with prostate cancer (Gcorr = 0.11 [0.03; 0.19]). There was a significant inverse association between the PRS for ovarian cancer and PD (odds ratio [OR] = 0.89 [0.84; 0.94]). Conversely, the PRS of PD was positively associated with breast cancer (OR = 1.08 [1.06; 1.10]) and inversely associated with ovarian cancer (OR = 0.95 [0.91; 0.99]). The association between PD and ovarian cancer was mostly driven by rs183211 located in an intron of the NSF gene (17q21.31).

CONCLUSIONS

We show evidence in favor of a contribution of pleiotropic genes to the association between PD and specific cancers. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Embracing Monogenic Parkinson's Disease: The MJFF Global Genetic PD Cohort

BACKGROUND

As gene-targeted therapies are increasingly being developed for Parkinson's disease (PD), identifying and characterizing carriers of specific genetic pathogenic variants is imperative. Only a small fraction of the estimated number of subjects with monogenic PD worldwide are currently represented in the literature and availability of clinical data and clinical trial-ready cohorts is limited.

OBJECTIVE

The objectives are to (1) establish an international cohort of affected and unaffected individuals with PD-linked variants; (2) provide harmonized and quality-controlled clinical characterization data for each included individual; and (3) further promote collaboration of researchers in the field of monogenic PD.

METHODS

We conducted a worldwide, systematic online survey to collect individual-level data on individuals with PD-linked variants in SNCA, LRRK2, VPS35, PRKN, PINK1, DJ-1, as well as selected pathogenic and risk variants in GBA and corresponding demographic, clinical, and genetic data. All registered cases underwent thorough quality checks, and pathogenicity scoring of the variants and genotype-phenotype relationships were analyzed.

RESULTS

We collected 3888 variant carriers for our analyses, reported by 92 centers (42 countries) worldwide. Of the included individuals, 3185 had a diagnosis of PD (ie, 1306 LRRK2, 115 SNCA, 23 VPS35, 429 PRKN, 75 PINK1, 13 DJ-1, and 1224 GBA) and 703 were unaffected (ie, 328 LRRK2, 32 SNCA, 3 VPS35, 1 PRKN, 1 PINK1, and 338 GBA). In total, we identified 269 different pathogenic variants; 1322 individuals in our cohort (34%) were indicated as not previously published.

CONCLUSIONS

Within the MJFF Global Genetic PD Study Group, we (1) established the largest international cohort of affected and unaffected individuals carrying PD-linked variants; (2) provide harmonized and quality-controlled clinical and genetic data for each included individual; (3) promote collaboration in the field of genetic PD with a view toward clinical and genetic stratification of patients for gene-targeted clinical trials. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

A Novel Nonsense Variant in GRM1 Causes Autosomal Recessive Spinocerebellar Ataxia 13 in a Consanguineous Pakistani Family

Background and objectives: Autosomal recessive spinocerebellar ataxia-13 (SCAR13) is an ultra-rare disorder characterized by slowly progressive cerebellar ataxia, cognitive deficiencies, and skeletal and oculomotor abnormalities. The objective of this case report is to expand the clinical and molecular spectrum of SCAR13. Methods: We investigated a consanguineous Pakistani family with four patients partially presenting with clinical features of SCAR13 using whole exome sequencing. Segregation analysis was performed by Sanger sequencing in all the available individuals of the family. Results: Patients presented with quadrupedal gait, delayed developmental milestones, non-progressive peripheral neuropathy, and cognitive impairment. Whole exome sequencing identified a novel pathogenic nonsense homozygous variant, Gly240*, in the gene GRM1 as a cause of SCAR13 that segregates with the recessive disease. Discussion: We report a novel homozygous nonsense variant in the GRM1 gene in four Pakistani patients presenting with clinical features that partially overlap with the already reported phenotype of SCAR13. In addition, the family presented quadrupedal gait and non-progressive symptoms, manifestations which have not been recognized previously. So far, only four variants in GRM1 have been reported, in families of Roma, Iranian, and Tunisian origins. The current study adds to the mutation spectrum of GRM1 and provides a rare presentation of SCAR13, the first from the Pakistani population.

The Interaction between HLA-DRB1 and Smoking in Parkinson's Disease Revisited

BACKGROUND

Two studies that examined the interaction between HLA-DRB1 and smoking in Parkinson's disease (PD) yielded findings in opposite directions.

OBJECTIVE

To perform a large-scale independent replication of the HLA-DRB1 × smoking interaction.

METHODS

We genotyped 182 single nucleotide polymorphism (SNPs) associated with smoking initiation in 12 424 cases and 9480 controls to perform a Mendelian randomization (MR) analysis in strata defined by HLA-DRB1.

RESULTS

At the amino acid level, a valine at position 11 (V11) in HLA-DRB1 displayed the strongest association with PD. MR showed an inverse association between genetically predicted smoking initiation and PD only in absence of V11 (odds ratio, 0.74, 95% confidence interval, 0.59-0.93, PInteraction  = 0.028). In silico predictions of the influence of V11 and smoking-induced modifications of α-synuclein on binding affinity showed findings consistent with this interaction pattern.

CONCLUSIONS

Despite being one of the most robust findings in PD research, the mechanisms underlying the inverse association between smoking and PD remain unknown. Our findings may help better understand this association. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Epigenome-wide association study of human frontal cortex identifies differential methylation in Lewy body pathology

Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are closely related progressive disorders with no available disease-modifying therapy, neuropathologically characterized by intraneuronal aggregates of misfolded α-synuclein. To explore the role of DNA methylation changes in PD and DLB pathogenesis, we performed an epigenome-wide association study (EWAS) of 322 postmortem frontal cortex samples and replicated results in an independent set of 200 donors. We report novel differentially methylated replicating loci associated with Braak Lewy body stage near TMCC2, SFMBT2, AKAP6 and PHYHIP. Differentially methylated probes were independent of known PD genetic risk alleles. Meta-analysis provided suggestive evidence for a differentially methylated locus within the chromosomal region affected by the PD-associated 22q11.2 deletion. Our findings elucidate novel disease pathways in PD and DLB and generate hypotheses for future molecular studies of Lewy body pathology.

Genome-wide Association and Meta-analysis of Age at Onset in Parkinson Disease: Evidence From the COURAGE-PD Consortium

BACKGROUND AND OBJECTIVES

Considerable heterogeneity exists in the literature concerning genetic determinants of the age at onset (AAO) of Parkinson disease (PD), which could be attributed to a lack of well-powered replication cohorts. The previous largest genome-wide association studies (GWAS) identified SNCA and TMEM175 loci on chromosome (Chr) 4 with a significant influence on the AAO of PD; these have not been independently replicated. This study aims to conduct a meta-analysis of GWAS of PD AAO and validate previously observed findings in worldwide populations.

METHODS

A meta-analysis was performed on PD AAO GWAS of 30 populations of predominantly European ancestry from the Comprehensive Unbiased Risk Factor Assessment for Genetics and Environment in Parkinson's Disease (COURAGE-PD) Consortium. This was followed by combining our study with the largest publicly available European ancestry dataset compiled by the International Parkinson Disease Genomics Consortium (IPDGC).

RESULTS

The COURAGE-PD Consortium included a cohort of 8,535 patients with PD (91.9%: Europeans and 9.1%: East Asians). The average AAO in the COURAGE-PD dataset was 58.9 years (SD = 11.6), with an underrepresentation of females (40.2%). The heritability estimate for AAO in COURAGE-PD was 0.083 (SE = 0.057). None of the loci reached genome-wide significance (p < 5 × 10-8). Nevertheless, the COURAGE-PD dataset confirmed the role of the previously published TMEM175 variant as a genetic determinant of the AAO of PD with Bonferroni-corrected nominal levels of significance (p < 0.025): (rs34311866: β(SE)COURAGE = 0.477(0.203), p COURAGE = 0.0185). The subsequent meta-analysis of COURAGE-PD and IPDGC datasets (Ntotal = 25,950) led to the identification of 2 genome-wide significant association signals on Chr 4, including the previously reported SNCA locus (rs983361: β(SE)COURAGE+IPDGC = 0.720(0.122), p COURAGE+IPDGC = 3.13 × 10-9) and a novel BST1 locus (rs4698412: β(SE)COURAGE+IPDGC = -0.526(0.096), p COURAGE+IPDGC = 4.41 × 10-8).

DISCUSSION

Our study further refines the genetic architecture of Chr 4 underlying the AAO of the PD phenotype through the identification of BST1 as a novel AAO PD locus. These findings open a new direction for the development of treatments to delay the onset of PD.

Paramedic Norwegian Acute Stroke Prehospital Project (ParaNASPP) study protocol: a stepped wedge randomised trial of stroke screening using the National Institutes of Health Stroke Scale in the ambulance

Background

Less than 50% of stroke patients in Norway reach hospital within 4 h of symptom onset. Early prehospital identification of stroke and triage to the right level of care may result in more patients receiving acute treatment. Quality of communication between paramedics and the stroke centre directly affects prehospital on-scene time, emphasising this as a key factor to reduce prehospital delay. Prehospital stroke scales are developed for quick and easy identification of stroke, but have poor sensitivity and specificity compared to an in-hospital assessment with the National Institutes of Health Stroke Scale (NIHSS). The aim of the Paramedic Norwegian Acute Stroke Prehospital Project (ParaNASPP) is to assess whether a structured learning program, prehospital NIHSS and a mobile application facilitating communication with the stroke physician may improve triage of acute stroke patients.

Methods

A stepped wedge cluster randomised controlled intervention design will be used in this trial in Oslo, Norway. Paramedics at five ambulance stations will enrol adult patients with suspected stroke within 24 h of symptom onset. All paramedics will begin in a control phase with standard procedures. Through an e-learning program and practical training, a random and sequential switch to the intervention phase takes place. A mobile application for NIHSS scoring, including vital patient information for treatment decisions, transferring data from paramedics to the on-call stroke physician at the Stroke Unit at Oslo University Hospital, will be provided for the intervention.

The primary outcome measure is positive predictive value (PPV) for prehospital identification of patients with acute stroke defined as the proportion of patients accepted for stroke evaluation and discharged with a final stroke diagnosis. One thousand three hundred patients provide a 50% surplus to the 808 patients needed for 80% power to detect a 10% increase in PPV.

Discussion

Structured and digital communication using a common scale like NIHSS may result in increased probability for better identification of stroke patients and less stroke mimics delivered to a stroke team for acute diagnostics and treatment in our population.

Trial registration

ClinicalTrials.govNCT04137874. Registered on October 24, 2019.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06006-4.

Subthalamic Nucleus Stimulation in Parkinson's Disease: 5-Year Extension Study of a Randomized Trial

Background

In Parkinson's disease (PD) long-term motor outcomes of subthalamic nucleus deep brain stimulation (STN-DBS) are well documented, while comprehensive reports on non-motor outcomes are fewer and less consistent.

Objective

To report motor and non-motor symptoms after 5-years of STN-DBS.

Methods

We performed an open 5-year extension study of a randomized trial that compared intraoperative verification versus mapping of STN using microelectrode recordings. Changes from preoperative to 5-years of STN-DBS were evaluated for motor and non-motor symptoms (MDS-UPDRS I-IV), sleep disturbances (PDSS), autonomic symptoms (Scopa-Aut), quality of life (PDQ-39) and cognition through a neuropsychological test battery. We evaluated whether any differences between the two randomization groups were still present, and assessed preoperative predictors of physical dependence after 5 years of treatment using logistic regression.

Results

We found lasting improvement of off-medication motor symptoms (total MDS-UPDRS III, bradykinetic-rigid symptoms and tremor), on-medication tremor, motor fluctuations, and sleep disturbances, but reduced performance across all cognitive domains, except verbal memory. Reduction of verbal fluency and executive function was most pronounced the first year and may thus be more directly related to the surgery than worsening in other domains. The group mapped with multiple microelectrode recordings had more improvement of bradykinetic-rigid symptoms and of PDQ-39 bodily discomfort sub-score, but also more reduction in word fluency. Older age was the most important factor associated with physical dependence after 5 years.

Conclusion

STN-DBS offers good long-term effects, including improved sleep, despite disease progression. STN-DBS surgery may negatively impact verbal fluency and executive function.

Dairy Intake and Parkinson's Disease: A Mendelian Randomization Study

BACKGROUND

Previous prospective studies highlighted dairy intake as a risk factor for Parkinson's disease (PD), particularly in men. It is unclear whether this association is causal or explained by reverse causation or confounding.

OBJECTIVE

The aim is to examine the association between genetically predicted dairy intake and PD using two-sample Mendelian randomization (MR).

METHODS

We genotyped a well-established instrumental variable for dairy intake located in the lactase gene (rs4988235) within the Courage-PD consortium (23 studies; 9823 patients and 8376 controls of European ancestry).

RESULTS

Based on a dominant model, there was an association between genetic predisposition toward higher dairy intake and PD (odds ratio [OR] per one serving per day = 1.70, 95% confidence interval = 1.12-2.60, P = 0.013) that was restricted to men (OR = 2.50 [1.37-4.56], P = 0.003; P-difference with women = 0.029).

CONCLUSIONS

Using MR, our findings provide further support for a causal relationship between dairy intake and higher PD risk, not biased by confounding or reverse causation. Further studies are needed to elucidate the underlying mechanisms. © 2022 International Parkinson and Movement Disorder Society.

Mendelian Randomisation Study of Smoking, Alcohol, and Coffee Drinking in Relation to Parkinson's Disease

BACKGROUND

Previous studies showed that lifestyle behaviors (cigarette smoking, alcohol, coffee) are inversely associated with Parkinson's disease (PD). The prodromal phase of PD raises the possibility that these associations may be explained by reverse causation.

OBJECTIVE

To examine associations of lifestyle behaviors with PD using two-sample Mendelian randomisation (MR) and the potential for survival and incidence-prevalence biases.

METHODS

We used summary statistics from publicly available studies to estimate the association of genetic polymorphisms with lifestyle behaviors, and from Courage-PD (7,369 cases, 7,018 controls; European ancestry) to estimate the association of these variants with PD. We used the inverse-variance weighted method to compute odds ratios (ORIVW) of PD and 95%confidence intervals (CI). Significance was determined using a Bonferroni-corrected significance threshold (p = 0.017).

RESULTS

We found a significant inverse association between smoking initiation and PD (ORIVW per 1-SD increase in the prevalence of ever smoking = 0.74, 95%CI = 0.60-0.93, p = 0.009) without significant directional pleiotropy. Associations in participants ≤67 years old and cases with disease duration ≤7 years were of a similar size. No significant associations were observed for alcohol and coffee drinking. In reverse MR, genetic liability toward PD was not associated with smoking or coffee drinking but was positively associated with alcohol drinking.

CONCLUSION

Our findings are in favor of an inverse association between smoking and PD that is not explained by reverse causation, confounding, and survival or incidence-prevalence biases. Genetic liability toward PD was positively associated with alcohol drinking. Conclusions on the association of alcohol and coffee drinking with PD are hampered by insufficient statistical power.

Investigation of Autosomal Genetic Sex Differences in Parkinson's Disease

OBJECTIVE

Parkinson's disease (PD) is a complex neurodegenerative disorder. Men are on average ~ 1.5 times more likely to develop PD compared to women with European ancestry. Over the years, genomewide association studies (GWAS) have identified numerous genetic risk factors for PD, however, it is unclear whether genetics contribute to disease etiology in a sex-specific manner.

METHODS

In an effort to study sex-specific genetic factors associated with PD, we explored 2 large genetic datasets from the International Parkinson's Disease Genomics Consortium and the UK Biobank consisting of 13,020 male PD cases, 7,936 paternal proxy cases, 89,660 male controls, 7,947 female PD cases, 5,473 maternal proxy cases, and 90,662 female controls. We performed GWAS meta-analyses to identify distinct patterns of genetic risk contributing to disease in male versus female PD cases.

RESULTS

In total, 19 genomewide significant regions were identified and no sex-specific effects were observed. A high genetic correlation between the male and female PD GWAS were identified (rg = 0.877) and heritability estimates were identical between male and female PD cases (~ 20%).

INTERPRETATION

We did not detect any significant genetic differences between male or female PD cases. Our study does not support the notion that common genetic variation on the autosomes could explain the difference in prevalence of PD between males and females cases at least when considering the current sample size under study. Further studies are warranted to investigate the genetic architecture of PD explained by X and Y chromosomes and further evaluate environmental effects that could potentially contribute to PD etiology in male versus female patients. ANN NEUROL 2021;90:41-48.

Impulsivity in Parkinson's disease patients treated with subthalamic nucleus deep brain stimulation-An exploratory study

BACKGROUND

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is a recognized treatment in Parkinson's disease (PD). Knowledge is still limited regarding the possible impact of STN-DBS on personality traits and the personality characteristics of PD patients who undergo surgery.

METHODS

To assess personality traits in relation to STN-DBS we did an ancillary protocol as part of a prospective randomized study that compared two surgical strategies. Patients were assessed with the Temperament and Character Inventory (TCI), the Urgency, Premeditation, Perseverance and Sensation Seeking impulse behavior scale, the Eysenck Personality Questionnaire (EPQ) and the Toronto Alexithymia Scale preoperatively and after one year of STN-DBS. EPQ and TCI baseline scores were compared with mean scores of healthy reference populations.

RESULTS

After 12-months of STN-DBS, there was a significant decline in Persistence compared to baseline. Preoperatively, the STN-DBS patients had significantly lower Persistence and Self-Transcendence scores, and significantly higher scores on Novelty-Seeking, Self-Directedness, Cooperativeness and on Social Conformity than referenced populations. No difference was found in Neuroticism or Harm-Avoidance scores. The baseline prevalence of alexithymia was low and at 1-year follow-up there was no significant change in alexithymia scores.

CONCLUSIONS

We found a higher baseline level of impulsivity in PD patients who underwent STN-DBS. After one year of STN-DBS, our results indicated that the treatment may affect the patients' personality by increasing certain aspects of impulsivity. There was no effect on alexithymia. The preoperative personality profile of PD patients might influence the outcome of STN-DBS.

APOE and MAPT Are Associated With Dementia in Neuropathologically Confirmed Parkinson's Disease

Introduction: Cognitive decline and dementia are common and debilitating non-motor phenotypic features of Parkinson's disease with a variable severity and time of onset. Common genetic variation of the Apolipoprotein E (APOE) and micro-tubule associated protein tau (MAPT) loci have been linked to cognitive decline and dementia in Parkinson's disease, although studies have yielded mixed results. To further elucidate the influence of APOE and MAPT variability on dementia in Parkinson's disease, we genotyped postmortem brain tissue samples of clinically and pathologically well-characterized Parkinson's donors and performed a survival analysis of time to dementia.

Methods: We included a total of 152 neuropathologically confirmed Parkinson's disease donors with or without clinical dementia during life. We genotyped known risk variants tagging the APOE ε4 allele and MAPT H1/H2 inversion haplotype. Cox proportional hazards regression analyses adjusted for age at onset, sex and genetic principal components were performed to assess the association between the genetic variants and time from motor onset to onset of dementia.

Results: We found that both the APOE ε4 allele (HR 1.82, 95 % CI 1.16–2.83, p = 0.009) and MAPT H1-haplotype (HR 1.71, 95 % CI 1.06–2.78, p = 0.03) were associated with earlier development of dementia in patients with Parkinson's disease.

Conclusion: Our results provide further support for the importance of APOE ε4 and MAPT H1-haplotype in the etiology of Parkinson's disease dementia, with potential future relevance for risk stratification and patient selection for clinical trials of therapies targeting cognitive decline in Parkinson's disease.

Subthalamic deep brain stimulation improves sleep and excessive sweating in Parkinson’s disease

Parkinson’s disease (PD) is a complex multisystem disorder with motor and non-motor symptoms (NMS). NMS may have an even greater impact on quality of life than motor symptoms. Subthalamic nucleus deep brain stimulation (STN-DBS) has been shown to improve motor fluctuations and quality of life, whereas the effects on different NMS have been less examined. Sleep disturbances and autonomic dysfunction are among the most prevalent NMS. We here report the efficacy of STN-DBS on sleep disturbances and autonomic dysfunction. In the parent trial, 60 patients were included in a single-center randomized prospective study, with MDS-UPDRS III and PDQ-39 as primary endpoints at 12 months of STN-DBS. Preplanned assessments at baseline and postoperatively at 3 and 12 months also included Parkinson’s Disease Sleep Scale (PDSS); Scopa-Aut; and MDS-UPDRS I, II, and IV. We found that STN-DBS had a significant and lasting positive effect on overall sleep quality, nocturnal motor symptoms and restlessness, and daytime dozing. Several aspects of autonomic dysfunction were also improved at 3 months postoperatively, although at 12 months only thermoregulation (sudomotor symptoms) remained significantly improved. We could not identify preoperative factors that predicted improvement in PDSS or Scopa-Aut. There was a close relationship between improved autonomic symptoms and improved quality of life after 1 year. NMS and especially sleep and autonomic dysfunction deserve more focus to improve patient outcomes further.

Differences in the Presentation and Progression of Parkinson's Disease by Sex

BACKGROUND

Previous studies reported various symptoms of Parkinson's disease (PD) associated with sex. Some were conflicting or confirmed in only one study.

OBJECTIVES

We examined sex associations to PD phenotypes cross-sectionally and longitudinally in large-scale data.

METHODS

We tested 40 clinical phenotypes, using longitudinal, clinic-based patient cohorts, consisting of 5946 patients, with a median follow-up of 3.1 years. For continuous outcomes, we used linear regressions at baseline to test sex-associated differences in presentation, and linear mixed-effects models to test sex-associated differences in progression. For binomial outcomes, we used logistic regression models at baseline and Cox regression models for survival analyses. We adjusted for age, disease duration, and medication use. In the secondary analyses, data from 17 719 PD patients and 7588 non-PD participants from an online-only, self-assessment PD cohort were cross-sectionally evaluated to determine whether the sex-associated differences identified in the primary analyses were consistent and unique to PD.

RESULTS

Female PD patients had a higher risk of developing dyskinesia early during the follow-up period, with a slower progression in activities of daily living difficulties, and a lower risk of developing cognitive impairments compared with male patients. The findings in the longitudinal, clinic-based cohorts were mostly consistent with the results of the online-only cohort.

CONCLUSIONS

We observed sex-associated contributions to PD heterogeneity. These results highlight the necessity of future research to determine the underlying mechanisms and importance of personalized clinical management. © 2020 International Parkinson and Movement Disorder Society.

Genetic modifiers of risk and age at onset in GBA associated Parkinson's disease and Lewy body dementia

Parkinson's disease is a genetically complex disorder. Multiple genes have been shown to contribute to the risk of Parkinson's disease, and currently 90 independent risk variants have been identified by genome-wide association studies. Thus far, a number of genes (including SNCA, LRRK2, and GBA) have been shown to contain variability across a spectrum of frequency and effect, from rare, highly penetrant variants to common risk alleles with small effect sizes. Variants in GBA, encoding the enzyme glucocerebrosidase, are associated with Lewy body diseases such as Parkinson's disease and Lewy body dementia. These variants, which reduce or abolish enzymatic activity, confer a spectrum of disease risk, from 1.4- to >10-fold. An outstanding question in the field is what other genetic factors that influence GBA-associated risk for disease, and whether these overlap with known Parkinson's disease risk variants. Using multiple, large case-control datasets, totalling 217 165 individuals (22 757 Parkinson's disease cases, 13 431 Parkinson's disease proxy cases, 622 Lewy body dementia cases and 180 355 controls), we identified 1691 Parkinson's disease cases, 81 Lewy body dementia cases, 711 proxy cases and 7624 controls with a GBA variant (p.E326K, p.T369M or p.N370S). We performed a genome-wide association study and analysed the most recent Parkinson's disease-associated genetic risk score to detect genetic influences on GBA risk and age at onset. We attempted to replicate our findings in two independent datasets, including the personal genetics company 23andMe, Inc. and whole-genome sequencing data. Our analysis showed that the overall Parkinson's disease genetic risk score modifies risk for disease and decreases age at onset in carriers of GBA variants. Notably, this effect was consistent across all tested GBA risk variants. Dissecting this signal demonstrated that variants in close proximity to SNCA and CTSB (encoding cathepsin B) are the most significant contributors. Risk variants in the CTSB locus were identified to decrease mRNA expression of CTSB. Additional analyses suggest a possible genetic interaction between GBA and CTSB and GBA p.N370S induced pluripotent cell-derived neurons were shown to have decreased cathepsin B expression compared to controls. These data provide a genetic basis for modification of GBA-associated Parkinson's disease risk and age at onset, although the total contribution of common genetics variants is not large. We further demonstrate that common variability at genes implicated in lysosomal function exerts the largest effect on GBA associated risk for disease. Further, these results have implications for selection of GBA carriers for therapeutic interventions.

Fine-Mapping of SNCA in Rapid Eye Movement Sleep Behavior Disorder and Overt Synucleinopathies

OBJECTIVE

Rapid eye movement sleep behavior disorder (RBD) is a prodromal synucleinopathy, as >80% will eventually convert to overt synucleinopathy. We performed an in-depth analysis of the SNCA locus to identify RBD-specific risk variants.

METHODS

Full sequencing and genotyping of SNCA was performed in isolated/idiopathic RBD (iRBD, n = 1,076), Parkinson disease (PD, n = 1,013), dementia with Lewy bodies (DLB, n = 415), and control subjects (n = 6,155). The iRBD cases were diagnosed with RBD prior to neurodegeneration, although some have since converted. A replication cohort from 23andMe of PD patients with probable RBD (pRBD) was also analyzed (n = 1,782 cases; n = 131,250 controls). Adjusted logistic regression models and meta-analyses were performed. Effects on conversion rate were analyzed in 432 RBD patients with available data using Kaplan-Meier survival analysis.

RESULTS

A 5'-region SNCA variant (rs10005233) was associated with iRBD (odds ratio [OR] = 1.43, p = 1.1E-08), which was replicated in pRBD. This variant is in linkage disequilibrium (LD) with other 5' risk variants across the different synucleinopathies. An independent iRBD-specific suggestive association (rs11732740) was detected at the 3' of SNCA (OR = 1.32, p = 4.7E-04, not statistically significant after Bonferroni correction). Homozygous carriers of both iRBD-specific SNPs were at highly increased risk for iRBD (OR = 5.74, p = 2E-06). The known top PD-associated variant (3' variant rs356182) had an opposite direction of effect in iRBD compared to PD.

INTERPRETATION

There is a distinct pattern of association at the SNCA locus in RBD as compared to PD, with an opposite direction of effect at the 3' of SNCA. Several 5' SNCA variants are associated with iRBD and with pRBD in overt synucleinopathies. ANN NEUROL 2020;87:584-598.

Genomewide association study of Parkinson's disease clinical biomarkers in 12 longitudinal patients' cohorts

BACKGROUND

Several reports have identified different patterns of Parkinson's disease progression in individuals carrying missense variants in GBA or LRRK2 genes. The overall contribution of genetic factors to the severity and progression of Parkinson's disease, however, has not been well studied.

OBJECTIVES

To test the association between genetic variants and the clinical features of Parkinson's disease on a genomewide scale.

METHODS

We accumulated individual data from 12 longitudinal cohorts in a total of 4093 patients with 22,307 observations for a median of 3.81 years. Genomewide associations were evaluated for 25 cross-sectional and longitudinal phenotypes. Specific variants of interest, including 90 recently identified disease-risk variants, were also investigated post hoc for candidate associations with these phenotypes.

RESULTS

Two variants were genomewide significant. Rs382940(T>A), within the intron of SLC44A1, was associated with reaching Hoehn and Yahr stage 3 or higher faster (hazard ratio 2.04 [1.58-2.62]; P value = 3.46E-8). Rs61863020(G>A), an intergenic variant and expression quantitative trait loci for α-2A adrenergic receptor, was associated with a lower prevalence of insomnia at baseline (odds ratio 0.63 [0.52-0.75]; P value = 4.74E-8). In the targeted analysis, we found 9 associations between known Parkinson's risk variants and more severe motor/cognitive symptoms. Also, we replicated previous reports of GBA coding variants (rs2230288: p.E365K; rs75548401: p.T408M) being associated with greater motor and cognitive decline over time, and an APOE E4 tagging variant (rs429358) being associated with greater cognitive deficits in patients.

CONCLUSIONS

We identified novel genetic factors associated with heterogeneity of Parkinson's disease. The results can be used for validation or hypothesis tests regarding Parkinson's disease. © 2019 International Parkinson and Movement Disorder Society.

Identification of novel risk loci, causal insights, and heritable risk for Parkinson's disease: a meta-analysis of genome-wide association studies

BACKGROUND

Genome-wide association studies (GWAS) in Parkinson's disease have increased the scope of biological knowledge about the disease over the past decade. We aimed to use the largest aggregate of GWAS data to identify novel risk loci and gain further insight into the causes of Parkinson's disease.

METHODS

We did a meta-analysis of 17 datasets from Parkinson's disease GWAS available from European ancestry samples to nominate novel loci for disease risk. These datasets incorporated all available data. We then used these data to estimate heritable risk and develop predictive models of this heritability. We also used large gene expression and methylation resources to examine possible functional consequences as well as tissue, cell type, and biological pathway enrichments for the identified risk factors. Additionally, we examined shared genetic risk between Parkinson's disease and other phenotypes of interest via genetic correlations followed by Mendelian randomisation.

FINDINGS

Between Oct 1, 2017, and Aug 9, 2018, we analysed 7·8 million single nucleotide polymorphisms in 37 688 cases, 18 618 UK Biobank proxy-cases (ie, individuals who do not have Parkinson's disease but have a first degree relative that does), and 1·4 million controls. We identified 90 independent genome-wide significant risk signals across 78 genomic regions, including 38 novel independent risk signals in 37 loci. These 90 variants explained 16-36% of the heritable risk of Parkinson's disease depending on prevalence. Integrating methylation and expression data within a Mendelian randomisation framework identified putatively associated genes at 70 risk signals underlying GWAS loci for follow-up functional studies. Tissue-specific expression enrichment analyses suggested Parkinson's disease loci were heavily brain-enriched, with specific neuronal cell types being implicated from single cell data. We found significant genetic correlations with brain volumes (false discovery rate-adjusted p=0·0035 for intracranial volume, p=0·024 for putamen volume), smoking status (p=0·024), and educational attainment (p=0·038). Mendelian randomisation between cognitive performance and Parkinson's disease risk showed a robust association (p=8·00 × 10^-7).

INTERPRETATION

These data provide the most comprehensive survey of genetic risk within Parkinson's disease to date, to the best of our knowledge, by revealing many additional Parkinson's disease risk loci, providing a biological context for these risk factors, and showing that a considerable genetic component of this disease remains unidentified. These associations derived from European ancestry datasets will need to be followed-up with more diverse data.

FUNDING

The National Institute on Aging at the National Institutes of Health (USA), The Michael J Fox Foundation, and The Parkinson's Foundation (see appendix for full list of funding sources).

Author Correction: GBA and APOE ε4 associate with sporadic dementia with Lewy bodies in European genome wide association study

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Frequency of Loss of Function Variants in LRRK2 in Parkinson Disease

Importance

Pathogenic variants in LRRK2 are a relatively common genetic cause of Parkinson disease (PD). Currently, the molecular mechanism underlying disease is unknown, and gain and loss of function (LOF) models of pathogenesis have been postulated. LRRK2 variants are reported to result in enhanced phosphorylation of substrates and increased cell death. However, the double knockout of Lrrk2 and its homologue Lrrk1 results in neurodegeneration in a mouse model, suggesting that disease may occur by LOF. Because LRRK2 inhibitors are currently in development as potential disease-modifying treatments in PD, it is critical to determine whether LOF variants in LRRK2 increase or decrease the risk of PD.

Objective

To determine whether LRRK1 and LRRK2 LOF variants contribute to the risk of developing PD.

Design, Setting, and Participants

To determine the prevailing mechanism of LRRK2-mediated disease in human populations, next-generation sequencing data from a large case-control cohort (>23 000 individuals) was analyzed for LOF variants in LRRK1 and LRRK2. Data were generated at 5 different sites and 5 different data sets, including cases with clinically diagnosed PD and neurologically normal control individuals. Data were collected from 2012 through 2017.

Main Outcomes and Measures

Frequencies of LRRK1 and LRRK2 LOF variants present in the general population and compared between cases and controls.

Results

Among 11 095 cases with PD and 12 615 controls, LRRK1 LOF variants were identified in 0.205% of cases and 0.139% of controls (odds ratio, 1.48; SE, 0.571; 95% CI, 0.45-4.44; P = .49) and LRRK2 LOF variants were found in 0.117% of cases and 0.087% of controls (odds ratio, 1.48; SE, 0.431; 95% CI, 0.63-3.50; P = .36). All association tests suggested lack of association between LRRK1 or LRRK2 variants and PD. Further analysis of lymphoblastoid cell lines from several heterozygous LOF variant carriers found that, as expected, LRRK2 protein levels are reduced by approximately half compared with wild-type alleles.

Conclusions and Relevance

Together these findings indicate that haploinsufficiency of LRRK1 or LRRK2 is neither a cause of nor protective against PD. Furthermore, these results suggest that kinase inhibition or allele-specific targeting of mutant LRRK2 remain viable therapeutic strategies in PD.

Genetic risk of Parkinson disease and progression:: An analysis of 13 longitudinal cohorts

OBJECTIVE

To determine if any association between previously identified alleles that confer risk for Parkinson disease and variables measuring disease progression.

METHODS

We evaluated the association between 31 risk variants and variables measuring disease progression. A total of 23,423 visits by 4,307 patients of European ancestry from 13 longitudinal cohorts in Europe, North America, and Australia were analyzed.

RESULTS

We confirmed the importance of GBA on phenotypes. GBA variants were associated with the development of daytime sleepiness (p.N370S: hazard ratio [HR] 3.28 [1.69-6.34]) and possible REM sleep behavior (p.T408M: odds ratio 6.48 [2.04-20.60]). We also replicated previously reported associations of GBA variants with motor/cognitive declines. The other genotype-phenotype associations include an intergenic variant near LRRK2 and the faster development of motor symptom (Hoehn and Yahr scale 3.0 HR 1.33 [1.16-1.52] for the C allele of rs76904798) and an intronic variant in PMVK and the development of wearing-off effects (HR 1.66 [1.19-2.31] for the C allele of rs114138760). Age at onset was associated with TMEM175 variant p.M393T (-0.72 [-1.21 to -0.23] in years), the C allele of rs199347 (intronic region of GPNMB, 0.70 [0.27-1.14]), and G allele of rs1106180 (intronic region of CCDC62, 0.62 [0.21-1.03]).

CONCLUSIONS

This study provides evidence that alleles associated with Parkinson disease risk, in particular GBA variants, also contribute to the heterogeneity of multiple motor and nonmotor aspects. Accounting for genetic variability will be a useful factor in understanding disease course and in minimizing heterogeneity in clinical trials.

Low prevalence of known pathogenic mutations in dominant PD genes: A Swedish multicenter study

OBJECTIVE

To determine the frequency of mutations known to cause autosomal dominant Parkinson disease (PD) in a series with more than 10% of Sweden's estimated number of PD patients.

METHODS

The Swedish Parkinson Disease Genetics Network was formed as a national multicenter consortium of clinical researchers who together have access to DNA from a total of 2,206 PD patients; 85.4% were from population-based studies. Samples were analyzed centrally for known pathogenic mutations in SNCA (duplications/triplications, p.Ala30Pro, p.Ala53Thr) and LRRK2 (p.Asn1437His, p.Arg1441His, p.Tyr1699Cys, p.Gly2019Ser, p.Ile2020Thr). We compared the frequency of these mutations in Swedish patients with published PD series and the gnomAD database.

RESULTS

A family history of PD in first- and/or second-degree relatives was reported by 21.6% of participants. Twelve patients (0.54%) carried LRRK2 p.(Gly2019Ser) mutations, one patient (0.045%) an SNCA duplication. The frequency of LRRK2 p.(Gly2019Ser) carriers was 0.11% in a matched Swedish control cohort and a similar 0.098% in total gnomAD, but there was a marked difference between ethnicities in gnomAD, with 42-fold higher frequency among Ashkenazi Jews than all others combined.

CONCLUSIONS

In relative terms, the LRRK2 p.(Gly2019Ser) variant is the most frequent mutation among Swedish or international PD patients, and in gnomAD. SNCA duplications were the second most common of the mutations examined. In absolute terms, however, these known pathogenic variants in dominant PD genes are generally very rare and can only explain a minute fraction of familial aggregation of PD. Additional genetic and environmental mechanisms may explain the frequent co-occurrence of PD in close relatives.

Parkinson's disease age at onset genome-wide association study: Defining heritability, genetic loci, and α-synuclein mechanisms

BACKGROUND

Increasing evidence supports an extensive and complex genetic contribution to PD. Previous genome-wide association studies (GWAS) have shed light on the genetic basis of risk for this disease. However, the genetic determinants of PD age at onset are largely unknown.

OBJECTIVES

To identify the genetic determinants of PD age at onset.

METHODS

Using genetic data of 28,568 PD cases, we performed a genome-wide association study based on PD age at onset.

RESULTS

We estimated that the heritability of PD age at onset attributed to common genetic variation was ∼0.11, lower than the overall heritability of risk for PD (∼0.27), likely, in part, because of the subjective nature of this measure. We found two genome-wide significant association signals, one at SNCA and the other a protein-coding variant in TMEM175, both of which are known PD risk loci and a Bonferroni-corrected significant effect at other known PD risk loci, GBA, INPP5F/BAG3, FAM47E/SCARB2, and MCCC1. Notably, SNCA, TMEM175, SCARB2, BAG3, and GBA have all been shown to be implicated in α-synuclein aggregation pathways. Remarkably, other well-established PD risk loci, such as GCH1 and MAPT, did not show a significant effect on age at onset of PD.

CONCLUSIONS

Overall, we have performed the largest age at onset of PD genome-wide association studies to date, and our results show that not all PD risk loci influence age at onset with significant differences between risk alleles for age at onset. This provides a compelling picture, both within the context of functional characterization of disease-linked genetic variability and in defining differences between risk alleles for age at onset, or frank risk for disease. © 2019 International Parkinson and Movement Disorder Society.

Essential tremor

Essential tremor affects almost 1 % of the population and may be very debilitating. Much is still unclear with regard to its pathophysiology, environmental factors and genetic causes. The diagnosis of essential tremor most likely encompasses several different conditions. In this article we provide an overview of essential tremor, pharmacological and neurosurgical treatment, as well as a review of the proposals for new definitions for tremor in general, and for essential tremor in particular.

No evidence for DNM3 as genetic modifier of age at onset in idiopathic Parkinson's disease

Parkinson's disease (PD) is a disorder with highly variable clinical phenotype. The identification of genetic variants modifying age at onset and other traits is of great interest because it may provide insight into disease mechanisms and potential therapeutic targets. A variant in the DNM3 gene (rs2421947) has been reported as a genetic modifier of age at onset in LRRK2-associated PD. To test the possible effect of genetic variation in DNM3 on age at onset in idiopathic PD, we examined rs2421947 in a total of 5918 patients with PD from seven data sets. We also assessed the potential effect of all common variants in the DNM3 locus. There was no significant association between rs2421947 and age at onset in any of the individual studies. Meta-analysis of the seven studies was nonsignificant and the between-study heterogeneity was minimal. No other common variants within the DNM3 locus affected age at onset. In conclusion, we find no evidence of an association between DNM3 variants and age at onset in idiopathic PD.

A comprehensive analysis of SNCA-related genetic risk in sporadic parkinson disease

OBJECTIVE

The goal of this study was to refine our understanding of disease risk attributable to common genetic variation in SNCA, a major locus in Parkinson disease, with potential implications for clinical trials targeting α-synuclein. We aimed to dissect the multiple independent association signals, stratify individuals by SNCA-specific risk profiles, and explore expression quantitative trait loci.

METHODS

We analyzed participant-level data from 12,503 patients and 12,502 controls, optimizing a risk model and assessing SNCA-specific risk scores and haplotypes as predictors of individual risk. We also explored hypotheses about functional mechanisms and correlated risk variants to gene expression in human brain and protein levels in cerebrospinal fluid.

RESULTS

We report and replicate a novel, third independent association signal at genome-wide significance level downstream of SNCA (rs2870004, p = 3.0*10^-8 , odds ratio [OR] = 0.88, 95% confidence interval [CI] = 0.84-0.92). SNCA risk score stratification showed a 2-fold difference in disease susceptibility between top and bottom quintiles (OR = 1.99, 95% CI = 1.78-2.23). Contrary to previous reports, we provide evidence supporting top variant rs356182 as functional in itself and associated with a specific SNCA 5' untranslated region transcript isoform in frontal cortex.

INTERPRETATION

The SNCA locus harbors a minimum of 3 independent association signals for Parkinson disease. We demonstrate a fine-grained stratification of α-synuclein-related genetic burden in individual patients of potential future clinical relevance. Further efforts to pinpoint the functional mechanisms are warranted, including studies of the likely causal top variant rs356182 and its role in regulating levels of specific SNCA mRNA transcript variants. Ann Neurol 2018;83:117-129.

Multiple Microelectrode Recordings in STN-DBS Surgery for Parkinson's Disease: A Randomized Study

Background

Subthalamic nucleus deep brain stimulation improves motor symptoms and fluctuations in advanced Parkinson's disease, but the degree of clinical improvement depends on accurate anatomical electrode placement. Methods used to localize the sensory‐motor part of the nucleus vary substantially. Using microelectrode recordings, at least three inserted microelectrodes are needed to obtain a three‐dimensional map. Therefore, multiple simultaneously inserted microelectrodes should provide better guidance than single sequential microelectrodes. We aimed to compare the use of multiple simultaneous versus single sequential microelectrode recordings on efficacy and safety of subthalamic nucleus stimulation.

Methods

Sixty patients were included in this double‐blind, randomized study, 30 in each group. Primary outcome measures were the difference from baseline to 12 months in the MDS‐UPDRS motor score (part III) in the off‐medication state and quality of life using the Parkinson's Disease Questionnaire‐39 (PDQ‐39) scores.

Results

The mean reduction of the MDS‐UPDRS III off score was 35 (SD 12) in the group investigated with multiple simultaneous microelectrodes compared to 26 (SD 10) in the single sequential microelectrode group (p = 0.004). The PDQ‐39 Summary Index did not differ between the groups, but the domain scores activities of daily living and bodily discomfort improved significantly more in the multiple microelectrodes group. The frequency of serious adverse events did not differ significantly.

Conclusions

After 12 months of subthalamic nucleus stimulation, the multiple microelectrodes group had a significantly greater improvement both in MDS‐UPDRS III off score and in two PDQ‐39 domains. Our results may support the use of multiple simultaneous microelectrode recordings.

Trial registration

http://ClinicalTrials.gov Identifier: NCT00855621 (first received March 3, 2009).

Risk variants of the α-synuclein locus and REM sleep behavior disorder in Parkinson's disease: a genetic association study

BACKGROUND

Parkinson's disease is a heterogeneous disorder where genetic factors may underlie clinical variability. Rapid eye movement sleep behavior disorder (RBD) is a parasomnia strongly linked to synucleinopathies, including Parkinson's disease. We hypothesized that SNCA variants conferring risk of Parkinson's disease would also predispose to an RBD phenotype.

METHODS

We assessed possible RBD (pRBD) status using the RBD screening questionnaire and investigated known susceptibility variants for Parkinson's disease located in the α-synuclein (SNCA) and tau (MAPT) gene loci in 325 Parkinson's disease patients. Associations between genetic risk variants and RBD were investigated by logistic regression, and an independent dataset of 382 patients from the Parkinson's Progression Marker Initiative (PPMI) study was used for replication.

RESULTS

pRBD was associated with rs3756063 located in the 5' region of SNCA (two-sided p = 0.018, odds ratio 1.44). We replicated this finding in the PPMI dataset (one-sided p = 0.036, odds ratio 1.35) and meta-analyzed the results (two-sided p = 0.0032, odds ratio 1.40). The Parkinson's disease risk variant in the 3' region of SNCA and the MAPT variant showed no association with pRBD.

CONCLUSIONS

Our findings provide proof of principle that a largely stable, dichotomous clinical feature of Parkinson's disease can be linked to a specific genetic susceptibility profile. Indirectly, it also supports the hypothesis of RBD as relevant marker for a distinct subtype of the disorder.

Insufficient evidence for pathogenicity of SNCA His50Gln (H50Q) in Parkinson's disease

SNCA missense mutations are a rare cause of autosomal dominant Parkinson's disease (PD). To date, 6 missense mutations in SNCA have been nominated as causal. Here, we assess the frequency of these 6 mutations in public population databases and PD case-control data sets to determine their true pathogenicity. We found that 1 of the 6 reported SNCA mutations, His50Gln, was consistently identified in large population databases, and no enrichment was evident in PD cases compared to controls. These results suggest that His50Gln is probably not a pathogenic variant. This information is important to provide counseling for His50Gln carriers and has implications for the interpretation of His50Gln α-synuclein functional investigations.

The GBA variant E326K is associated with Parkinson's disease and explains a genome-wide association signal

OBJECTIVE

Coding variants in the GBA gene have been identified as the numerically most important genetic risk factors for Parkinson's disease (PD). In addition, genome-wide association studies (GWAS) have identified associations with PD in the SYT11-GBA region on chromosome 1q22, but the relationship to GBA coding variants have remained unclear. The aim of this study was to sequence the complete GBA gene in a clinical cohort and to investigate whether coding variants within the GBA gene may be driving reported association signals.

METHODS

We analyzed high-throughput sequencing data of all coding exons of GBA in 366 patients with PD. The identified low-frequency coding variants were genotyped in three Scandinavian case-controls series (786 patients and 713 controls). Previously reported risk variants from two independent association signals within the SYT11-GBA locus on chromosome 1 were also genotyped in the same samples. We performed association analyses and evaluated linkage disequilibrium (LD) between the variants.

RESULTS

We identified six rare mutations (1.6%) and two low-frequency coding variants in GBA. E326K (rs2230288) was significantly more frequent in PD patients compared to controls (OR 1.65, p=0.03). There was no clear association of T369M (rs75548401) with disease (OR 1.43, p=0.24). Genotyping the two GWAS hits rs35749011 and rs114138760 in the same sample set, we replicated the association between rs35749011 and disease status (OR 1.67, p=0.03), while rs114138760 was found to have similar allele frequencies in patients and controls. Analyses revealed that E326K and rs35749011 are in very high LD (r² 0.95).

CONCLUSIONS

Our results confirm that the GBA variant E326K is a susceptibility allele for PD. The results suggest that E326K may fully account for the primary association signal observed at chromosome 1q22 in previous GWAS of PD.

Targeted high throughput sequencing in hereditary ataxia and spastic paraplegia

Hereditary ataxia and spastic paraplegia are heterogeneous monogenic neurodegenerative disorders. To date, a large number of individuals with such disorders remain undiagnosed. Here, we have assessed molecular diagnosis by gene panel sequencing in 105 early and late-onset hereditary ataxia and spastic paraplegia probands, in whom extensive previous investigations had failed to identify the genetic cause of disease. Pathogenic and likely-pathogenic variants were identified in 20 probands (19%) and variants of uncertain significance in ten probands (10%). Together these accounted for 30 probands (29%) and involved 18 different genes. Among several interesting findings, dominantly inherited KIF1A variants, p.(Val8Met) and p.(Ile27Thr) segregated in two independent families, both presenting with a pure spastic paraplegia phenotype. Two homozygous missense variants, p.(Gly4230Ser) and p.(Leu4221Val) were found in SACS in one consanguineous family, presenting with spastic ataxia and isolated cerebellar atrophy. The average disease duration in probands with pathogenic and likely-pathogenic variants was 31 years, ranging from 4 to 51 years. In conclusion, this study confirmed and expanded the clinical phenotypes associated with known disease genes. The results demonstrate that gene panel sequencing and similar sequencing approaches can serve as efficient diagnostic tools for different heterogeneous disorders. Early use of such strategies may help to reduce both costs and time of the diagnostic process.

Low frequency of GCH1 and TH mutations in Parkinson's disease

BACKGROUND

The causes of Parkinson's disease (PD) are unknown in the majority of patients. The GCH1 gene encodes GTP-cyclohydrolase I, an important enzyme in dopamine synthesis. Co-occurrence of dopa-responsive dystonia (DRD) and a PD phenotype has been reported in families with GCH1 mutations. Recently, rare coding variants in GCH1 were found to be enriched in PD patients, indicating a role for the enzyme in the neurodegenerative process.

METHODS

To further elucidate the contribution of GCH1 mutations to sporadic PD, we examined its coding exons in a targeted deep sequencing study of 509 PD patients (mean age at onset 56.7 ± 12.0 years) and 230 controls. We further included the tyrosine hydroxylase gene TH, also known to cause DRD. Gene dose assessments were performed to screen for large copy number variants in a subset of 48 patients with early-onset PD.

RESULTS

No putatively pathogenic GCH1 mutations were found. The frequency of rare heterozygous variants in the TH gene was 0.69% (7/1018) in the patient group and 0.22% (1/460) in the control group (p = 0.45).

CONCLUSIONS

Previous studies have found that coding variants in the GCH1 gene may be considered a risk factor for PD. Our study indicates that mutations in GCH1 are rare in late-onset PD. Several patients carried heterozygous variants in the TH gene that may affect protein function. Our study was not designed to determine with certainty if any of these variants play a role as risk factors for late-onset PD.

A cumulative genetic risk score predicts progression in Parkinson's disease

BACKGROUND

The contribution of genetic variability to clinical heterogeneity in Parkinson's disease is insufficiently understood. We aimed to investigate the effect of cumulative genetic risk on clinical outcomes.

METHODS

In a single-center study of 336 patients we genotyped 19 independent susceptibility variants identified in genome-wide association studies of Parkinson's disease. We tested for association between a cumulative genetic risk score and 3 outcome measures: survival, time until progression to Hoehn and Yahr stage 3, and Unified Parkinson's Disease Rating Scale motor score severity.

RESULTS

Genetic risk score was significantly associated with time from diagnosis to Hoehn and Yahr stage 3 in a Cox regression model (P = 0.010). We observed no clear association for the other outcomes.

CONCLUSIONS

We present results linking cumulative genetic risk to a motor outcome in Parkinson's disease. Our findings provide a valuable starting point for future large-scale efforts to map the genetic determinants of phenotypic variability.