International Parkinson Disease Genomics Consortium Research Articles

Association of Body Mass Index and Parkinson Disease: A Bidirectional Mendelian Randomization Study.

The role of body mass index (BMI) in Parkinson disease (PD) is unclear. Based on the Comprehensive Unbiased Risk Factor Assessment for Genetics and Environment in PD (Courage-PD) consortium, we used 2-sample Mendelian randomization (MR) to replicate a previously reported inverse association of genetically predicted BMI with PD and investigated whether findings were robust in analyses addressing the potential for survival and incidence-prevalence biases. We also examined whether the BMI-PD relation is bidirectional by performing a reverse MR. We used summary statistics from a genome-wide association study (GWAS) to extract the association of 501 single-nucleotide polymorphisms (SNPs) with BMI and from the Courage-PD and international Parkinson Disease Genomics Consortium (iPDGC) to estimate their association with PD. Analyses are based on participants of European ancestry. We used the inverse-weighted method to compute odds ratios (ORIVW per 4.8 kg/m2 [95% CI]) of PD and additional pleiotropy robust methods. We performed analyses stratified by age, disease duration, and sex. For reverse MR, we used SNPs associated with PD from 2 iPDGC GWAS to assess the effect of genetic liability toward PD on BMI. Summary statistics for BMI are based on 806,834 participants (54% women). Summary statistics for PD are based on 8,919 (40% women) cases and 7,600 (55% women) controls from Courage-PD, and 19,438 (38% women) cases and 24,388 (51% women) controls from iPDGC. In Courage-PD, we found an inverse association between genetically predicted BMI and PD (ORIVW 0.82 [0.70-0.97], p = 0.012) without evidence for pleiotropy. This association tended to be stronger in younger participants (≤67 years, ORIVW 0.71 [0.55-0.92]) and cases with shorter disease duration (≤7 years, ORIVW 0.75 [0.62-0.91]). In pooled Courage-PD + iPDGC analyses, the association was stronger in women (ORIVW 0.85 [0.74-0.99], p = 0.032) than men (ORIVW 0.92 [0.80-1.04], p = 0.18), but the interaction was not statistically significant (p-interaction = 0.48). In reverse MR, there was evidence for pleiotropy, but pleiotropy robust methods showed a significant inverse association. Using an independent data set (Courage-PD), we replicate an inverse association of genetically predicted BMI with PD, not explained by survival or incidence-prevalence biases. Moreover, reverse MR analyses support an inverse association between genetic liability toward PD and BMI, in favor of a bidirectional relation.

Association between the sarcopenia-related traits and Parkinson's disease: A bidirectional two-sample Mendelian randomization study

ObjectiveTo explore the causal association between sarcopenia-related traits and Parkinson's disease by Mendelian randomization (MR) approach. MethodsA genome-wide association study (GWAS) of sarcopenia-related traits was done at the UK Biobank (UKB). The traits were appendicular lean mass, low hand grip strength (including the European Working Group on Sarcopenia in Older People (EWGSOP) and the Foundation for the National Institutes of Health (FNIH) criteria and usual walking pace. The International Parkinson's Disease Genomics Consortium (IPDGC) gave us GWAS data for Parkinson's disease (PD). We used three different types of MR analyses: including Inverse-variance weighted (IVW), Mendelian randomized Egger regression (MR-Egger), and weighted median methods (both weighted and simple modes). ResultsThe MR analysis showed that low hand grip strength was negatively associated with the risk of developing Parkinson's disease, including EWGSOP criterion (odds ratio (OR) = 0.734; 95% confidence interval (CI) = 0.575–0.937, P = 0.013) and FNIH criterion (OR = 0.619; 95% CI = 0.419–0.914, P = 0.016), and usual walking pace was also a risk factor for Parkinson's disease (OR = 3.307, 95% CI = 1.277–8.565, P = 0.014). ConclusionsIn European population, low hand grip strength is negatively associated with the risk of developing Parkinson's disease, and usual walking pace is also a risk factor for Parkinson's disease. Further exploration of the potential genetic mechanisms underlying hand grip strength and Parkinson's disease and the potential relationship between walking pace, balance, and falls in Parkinson's patients may help to reduce the burden of sarcopenia and Parkinson's disease.

Bidirectional two-sample Mendelian randomization analysis identifies causal associations between oxidative stress and Parkinson's disease.

Observational studies have shown that oxidative stress (OS) is associated with Parkinson's disease (PD). However, whether such observations reflect cause-effect remains largely unknown. To test this, we performed a two-sample bidirectional Mendelian randomization (MR) analysis to investigate the causal-effects between OS biomarkers and PD. We selected summary statistics data for single-nucleotide polymorphisms (SNPs) associated with catalase (n = 13), glutathione peroxidases (n = 12), superoxide dismutase (n = 13), vitamin A (n = 7), vitamin C (n = 10), vitamin E (n = 12), vitamin B12 (n = 8), folate (n = 14), copper (n = 6), Zinc (n = 7), and iron (n = 23) levels, and the corresponding data for PD from the International Parkinson Disease Genomics Consortium (IPDGC, 33,674 cases and 449,056 controls). Inverse-variance weighted (IVW) MR analyses were conducted to estimate associations of OS with PD. Reverse MR analysis was further performed to predict the causal effects of PD on the above OS biomarkers. As for PD, the IVW method suggested that the Zinc (Zn) levels was significantly associated with PD (OR = 1.107, 95% CI 1.013-1.211; p = 0.025), which is consistent with results from the weighted median analyses. Moreover, the results remained consistent and robust in the sensitivity analysis. However, there were no significant associations of catalase, glutathione peroxidases, superoxide dismutase, vitamin A, vitamin C, vitamin E, vitamin B12, folate, copper, or iron with PD. As for OS, our reverse MR analysis also did not support a causal effect of liability to PD on OS. The MR study supported the causal effect of Zn on PD. These findings may inform prevention strategies and interventions directed toward OS and PD.

X-Chromosome Association Study in Latin American Cohorts Identifies New Loci in Parkinson's Disease.

Sex differences in Parkinson's disease (PD) risk are well-known. However, the role of sex chromosomes in the development and progression of PD is still unclear. The objective of this study was to perform the first X-chromosome-wide association study for PD risk in a Latin American cohort. We used data from three admixed cohorts: (1) Latin American Research consortium on the Genetics of Parkinson's Disease (n = 1504) as discover cohort, and (2) Latino cohort from International Parkinson Disease Genomics Consortium (n = 155) and (3) Bambui Aging cohort (n = 1442) as replication cohorts. We also developed an X-chromosome framework specifically designed for admixed populations. We identified eight linkage disequilibrium regions associated with PD. We replicated one of these regions (top variant rs525496; discovery odds ratio [95% confidence interval]: 0.60 [0.478-0.77], P = 3.13 × 10-5 replication odds ratio: 0.60 [0.37-0.98], P = 0.04). rs5525496 is associated with multiple expression quantitative trait loci in brain and non-brain tissues, including RAB9B, H2BFM, TSMB15B, and GLRA4, but colocalization analysis suggests that rs5525496 may not mediate risk by expression of these genes. We also replicated a previous X-chromosome-wide association study finding (rs28602900), showing that this variant is associated with PD in non-European populations. Our results reinforce the importance of including X-chromosome and diverse populations in genetic studies. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

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

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. 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. 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. 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). 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.

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

Background and ObjectivesConsiderable 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.MethodsA 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).ResultsThe 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), pCOURAGE = 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), pCOURAGE+IPDGC = 3.13 × 10−9) and a novel BST1 locus (rs4698412: β(SE)COURAGE+IPDGC = −0.526(0.096), pCOURAGE+IPDGC = 4.41 × 10−8).DiscussionOur 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.

A glimpse of the genetics of young-onset Parkinson's disease in Central Asia.

ABSTRACTBackgroundKnowledge of the genetic background of many human diseases is currently lacking from genetically undiscovered regions, including Central Asia. Kazakhstan is the first Central Asian country where the genetic studies of Parkinson's disease (PD) have been emerging since it had become a member of the International Parkinson Disease Genomics Consortium. Here we report on the results of whole‐exome sequencing (WES) in 50 young‐onset PD (YOPD) cases from Kazakhstan.MethodologyWES was performed on 50 unrelated individuals with YOPD from Kazakhstan. Exome data were screened for novel/ultra‐rare deleterious variants in known and candidate PD genes. Copy number variants and small indels were also called.ResultsOnly three cases (6%) were found to be positive for known PD genes including two unrelated familial PD cases with LRRK2 p.(Arg1441Cys) and one case with a homozygous pathogenic PRKN p.(Arg84Trp) variant. Four cases had novel and ultra‐rare variants of uncertain significance in LRRK2, DNAJC13, and VPS35. Novel deleterious variants were found in candidate Mendelian PD genes including CSMD1, TNR, EIF4G1, and ATP13A3. Eight cases harbored the East Asian‐specific LRRK2 p.(Ala419Val) variant.ConclusionsThe low diagnostic yield in our study might imply that a significant proportion of YOPD cases in Central Asia remains unresolved. Therefore, a better understanding of the genetic architecture of PD among populations of Central Asian ancestry and the pathogenicity of numerous rare variants should be further investigated. WES is a valuable technique for large‐scale YOPD genetic studies in Central Asia.

Lack of evidence for association of UQCRC1 with Parkinson's disease in Europeans

Recently, a novel variant p.Y314S in UQCRC1 has been implicated as pathogenic in Parkinson's disease (PD). In the present study, we aimed to examine the association of UQCRC1 with PD in large cohorts of European origin. We examined common and rare genetic variation in UQCRC1 using genome-wide association study data from the International Parkinson Disease Genomics Consortium, including 14,671 cases and 17,667 controls, and whole-genome sequencing data from the Accelerating Medicines Partnership–Parkinson's disease initiative, including 1647 patients with PD and 1050 controls. No common variants were consistently associated with PD, and a variety of burden analyses did not reveal an association between rare variants in UQCRC1 and PD. Therefore, our results do not support a major role for UQCRC1 in PD in the European population, and additional studies in other populations are warranted.

The role of RHOT1 and RHOT2 genetic variation on Parkinson disease risk and onset

Genetic variation within the mitochondrial pathway contributes to the risk of Parkinson’s disease (PD). Recent genetic analyses have investigated the association between the RHOT1 and RHOT2 genes and PD etiology. Furthermore, 4 mutations in the RHOT1 gene (p.R272Q, p.R450C, p.T351A, p.T610A) have been reported to be potentially associated with disease risk. As part of the International Parkinson Disease Genomics Consortium efforts to evaluate reported PD risk factors, we assessed the role of common and low frequency variants in both RHOT1 and also RHOT2 according to the high degree of homology in their amino acid sequences. Utilizing large-scale genotyping and whole-genome sequencing data from the International Parkinson Disease Genomics Consortium and the Accelerating Medicines Partnership – Parkinson Disease initiative, our analyses did not identify evidence to support the hypothesis that RHOT1 and RHOT2 are disease causing or modifying genes for PD risk or age at onset.

Ten Years of the International Parkinson Disease Genomics Consortium: Progress and Next Steps.

In June 2009 a small group of investigators met at the annual Movement Disorders Society meeting in Paris. The explicit goal of this meeting was to discuss a potential research alliance focused on the genetics of Parkinson disease (PD). The outcome of this informal meeting was the creation of the International Parkinson Disease Genomics Consortium (IPDGC), a group focused on collaborative genetics research, enabled by trust, sharing, and as little paperwork as possible. The IPDGC has grown considerably since its inception, including over 100 scientists from around the World. The focus has also grown, to include clinical and functional investigation of PD at scale. Most recently, the IPDGC has expanded to initiate major research efforts in East Asia and Africa, and has prioritized collaborations with ongoing major efforts in India and South America. Here we summarize the efforts of the IPDGC thus far and place these in the context of a decade of progress in PD genomics. We also discuss the future direction of IPDGC and our stated research priorities for the next decade.

The Role of Rare Coding Variants in Parkinson's Disease GWAS Loci.

Introduction: Genome-wide association studies (GWAS) have identified multiple loci associated with Parkinson's disease (PD) risk. The presence of rare variants within these loci that may account for the increased susceptibility requires further investigation.Methods: Using exome sequencing, we performed a comprehensive rare variant screen of genes located within 56 novel PD loci. We first analyzed exomes from 109 subjects in the discovery cohort (85 diagnosed with PD and 24 healthy controls) and filtered for rare coding variants with minor allele frequency <0.01 and combined annotation-dependent depletion > 15. Further investigation of exome data from a replication cohort of 2,859 European patients with PD (International Parkinson's Disease Genomics Consortium) and 24,146 non-Finnish European controls from gnomAD were used for association testing of specific rare variants found in the discovery cohort.Results: Our genetic screening identified 54 potential disease-relevant variants in 71 genes in 109 subjects. Six out of 54 variants were found in two or more patients and were not observed in healthy controls: DNAH1 p.A3639T, STAB1 p.S1089G, ANK2 p.V3634D, ANK2 p.R3906W, SH3GL2 p.G276V, and NOD2 p.G908R. Replication in the International Parkinson's Disease Genomics Consortium (IPDGC) confirmed the association with PD risk for three out of the six identified variants (STAB1 p.S1089G, SH3GL2 p.G276V, and NOD2 p.G908R) (p < 10−3).Conclusion: Our study suggests that some of the associations identified in PD risk loci can be ascribed to rare variants with likely functional effects that modify PD risk.

Utility and implications of exome sequencing in early-onset Parkinson's disease.

Although the genetic load is high in early-onset Parkinson's disease, thorough investigation of the genetic diagnostic yield has yet to be established. The objectives of this study were to assess variants in known genes for PD and other movement disorders and to find new candidates in 50 patients with early-onset PD. We searched for variants either within genes listed by the International Parkinson and Movement Disorder Society Task Force on Genetic Nomenclature or rare homozygous variants in novel candidate genes. Further, exome data from 1148 European PD patients (International Parkinson Disease Genomics Consortium) were used for association testing. Seven patients (14%) carried pathogenic or likely pathogenic variants in Parkin, PLA2G6, or GBA. In addition, rare missense variants in DNAJC13:p.R1830C and in PPM1K:p.Y352C were detected. SPG7:p.A510V and PPM1K:p.Y352C revealed significant association with PD risk (P < 0.05). Although we identified pathogenic variants in 14% of our early-onset PD patients, the majority remain unexplained, and novel candidates need to be validated independently to better further evaluate their role in PD. © 2018 International Parkinson and Movement Disorder Society.

A Nonsynonymous Mutation in PLCG2 Reduces the Risk of Alzheimer's Disease, Dementia with Lewy-Bodies and Frontotemporal Dementia, and Increases the Likelihood of Longevity

Background: PLCG2 plays an important role in immune system signaling, and is expressed in several immune cell types including microglia in the brain. In 2017, the genetic variant rs72824905 (p.Pro522Arg) in the PLCG2 gene (Phospholipase C Gamma 2) was associated with a reduced risk of Alzheimer's disease (AD). Here we investigated whether the rs72824905 variant had a similar protective effect on six other brain diseases. We further tested if rs72824905 increases the likelihood of longevity, since a reduced risk of neurodegenerative diseases might associate with general survival. Methods: We investigated the effect of carrying rs72824905 on disease risk in a total of 53,627 patients with one of seven brain diseases. We studied AD (N = 4,985), frontotemporal dementia (FTD) (N = 2,437), dementia with Lewy-bodies (DLB) (N = 1,446), progressive supranuclear palsy (PSP) (N = 882), Parkinson's disease (PD) (N = 28,448) amyotrophic lateral sclerosis (ALS) (N = 10,953) and multiple sclerosis (MS) (N = 4,476) by comparing them with in total 149,290 controls using logistic regression models. Next, we studied the effect of carrying rs72824905 on longevity by comparing individuals who reached at least 90 years (N = 3,516) with individuals who died before age 90 years or were last screened before 90 years (N = 9,677). In addition, we studied the association of rs72824905 with survival after the age of 90 in a subset of long-lived individuals followed until death. Finally, we supported our findings by studying by-proxy phenotypes in the ~450.000 participants of the UK Biobank. We associated the rs72824905 genotypes of UK Biobank participants with parental history of dementia as proxy for dementia and as a proxy for longevity we studied parental age over 90 as well as parental age over 95 years of age. All individuals were of European ancestry. Results: The rs72824905-G allele associated with a reduced AD risk (Odds ratio (OR) = 0·57, p = 4·7×10-4), a reduced DLB risk (OR = 0·54, p = 4·5×10-2) and reduced FTD risk (OR = 0·61, p = 1·0×10 2). We did not find evidence for association of rs72824905 with the risks of PSP (OR = 1·46, p = 0·19), PD (OR = 1·18, p = 0·10), ALS (OR = 1·07, p = 0·26) or MS (OR = 0·99, p = 0·95). The rs72824905-G allele was associated with a 1·49 increased likelihood of reaching >90 years (p = 6.4×10-3): variant carriers lived longer after the age of 90 years, median 4.7 (inter quartile range = 1·9 - 7·4) years compared to non-carriers 3.3 (IQR = 1·4 - 5·8) (Hazard ratio = 0·75, p = 0·07). By-proxy analyses supported the associations of rs728824905 with dementia as well as longevity. Variant carriers had a lower likelihood of having a parent with dementia (OR = 0·88, p = 1·8×10 3) and had a significantly increased likelihood of having a parent aged >95 years (OR = 1·19, p = 2·1×10-2). Conclusions: Our results show that rs72824905 in PLCG2 protects from AD, DLB and FTD and increases the likelihood of longevity. Together, our findings highlight a central role for PLCG2 related immune signaling in the brain, which should be the subject of future studies as a drug target for multiple brain diseases. Funding Statement: The authors present a short description of 16 cohorts, often including multiple sites or studies, that contributed to this manuscript and their funding sources in Supplementary Table 1: Amsterdam dementia Cohort (ADC), 100-Plus study, German Study on Ageing, Cognition and Dementia in Primary Care Patients (AgeCoDe), Brain compendium, Clinical AD, Sweden, Danish data, Fundacio ACE (FACE), Genetics of Healthy Ageing Study (GEHA – NL), Gothenburg Birth Cohort (GBC) Studies, International FTD-Genomics Consortium (IFGC), Kompetenznetz Multiple Sklerose (KKNMS), Longitudinal Aging Study Amsterdam (LASA), Leiden Longevity Study, Maria Carolina Dalmasso, Mayo Clinic AD, DLB, PD, PSP, NDRU cohort, Oviedo, Pascual Sanchez-Juan, Project MinE, Risk and modifying factors in Fronto Temporal Dementia (RiMoD-FTD): follows The SPIN cohort, San Sebastian, UK Biobank analysis, IPDGC (The International Parkinson Disease Genomics Consortium). Declaration of Interests: The authors declare no competing interest related to this work. Ethics Approval Statement: Studies were approved by corresponding ethics committees and informed consent was obtained for all participants.

A Two-Stage Meta-Analysis Identifies Several New Loci for Parkinson's Disease

A previous genome-wide association (GWA) meta-analysis of 12,386 PD cases and 21,026 controls conducted by the International Parkinson's Disease Genomics Consortium (IPDGC) discovered or confirmed 11 Parkinson's disease (PD) loci. This first analysis of the two-stage IPDGC study focused on the set of loci that passed genome-wide significance in the first stage GWA scan. However, the second stage genotyping array, the ImmunoChip, included a larger set of 1,920 SNPs selected on the basis of the GWA analysis. Here, we analyzed this set of 1,920 SNPs, and we identified five additional PD risk loci (combined p<5×10−10, PARK16/1q32, STX1B/16p11, FGF20/8p22, STBD1/4q21, and GPNMB/7p15). Two of these five loci have been suggested by previous association studies (PARK16/1q32, FGF20/8p22), and this study provides further support for these findings. Using a dataset of post-mortem brain samples assayed for gene expression (n = 399) and methylation (n = 292), we identified methylation and expression changes associated with PD risk variants in PARK16/1q32, GPNMB/7p15, and STX1B/16p11 loci, hence suggesting potential molecular mechanisms and candidate genes at these risk loci.