Frequency of mutations in PRKN, PINK1, and DJ1 in Patients With Early-Onset Parkinson Disease from neighboring countries in Central Europe.

INTRODUCTION: Approximately 10% of patients with Parkinson disease (PD) present with early-onset disease (EOPD), defined as diagnosis before 50 years of age. Genetic factors are known to contribute to EOPD, with most commonly observed mutations in PRKN, PINK1, and DJ1 genes. The aim of our study was to analyze the frequency of PRKN, PINK1, and DJ1 mutations in an EOPD series from 4 neighboring European countries: Czech Republic, Germany, Poland, and Ukraine. METHODS: Diagnosis of PD was made based on UK Brain Bank diagnostic criteria in departments experienced in movement disorders (1 from Czech Republic, 1 from Germany, 9 from Poland, and 3 from Ukraine). EOPD was defined as onset at or before 50 years of age. Of the 541 patients recruited to the study, 11 were Czech, 38 German, 476 Polish, and 16 Ukrainian. All cohorts were fully screened with Sanger sequencing for PRKN, PINK1, and DJ1 and multiplex ligation-dependent probe amplification for exon dosage. RESULTS: PRKN homozygous or double heterozygous mutations were identified in 17 patients: 1 Czech (9.1%), 1 German (2.6%), 14 Polish (2.9%), and 1 Ukrainian (6.3%). PINK1 homozygous mutations were only identified in 3 Polish patients (0.6%). There were no homozygous or compound heterozygous DJ1 mutations in analyzed subpopulations. One novel variant in PRKN was identified in the Ukrainian series. CONCLUSION: In the analyzed cohorts, mutations in the genes PRKN, PINK1, and DJ1 are not frequently observed.

Large-scale assessment of polyglutamine repeat expansions in Parkinson disease.

OBJECTIVES: We aim to clarify the pathogenic role of intermediate size repeat expansions of SCA2, SCA3, SCA6, and SCA17 as risk factors for idiopathic Parkinson disease (PD). METHODS: We invited researchers from the Genetic Epidemiology of Parkinson's Disease Consortium to participate in the study. There were 12,346 cases and 8,164 controls genotyped, for a total of 4 repeats within the SCA2, SCA3, SCA6, and SCA17 genes. Fixed- and random-effects models were used to estimate the summary risk estimates for the genes. We investigated between-study heterogeneity and heterogeneity between different ethnic populations. RESULTS: We did not observe any definite pathogenic repeat expansions for SCA2, SCA3, SCA6, and SCA17 genes in patients with idiopathic PD from Caucasian and Asian populations. Furthermore, overall analysis did not reveal any significant association between intermediate repeats and PD. The effect estimates (odds ratio) ranged from 0.93 to 1.01 in the overall cohort for the SCA2, SCA3, SCA6, and SCA17 loci. CONCLUSIONS: Our study did not support a major role for definite pathogenic repeat expansions in SCA2, SCA3, SCA6, and SCA17 genes for idiopathic PD. Thus, results of this large study do not support diagnostic screening of SCA2, SCA3, SCA6, and SCA17 gene repeats in the common idiopathic form of PD. Likewise, this largest multicentered study performed to date excludes the role of intermediate repeats of these genes as a risk factor for PD.

Early-onset Parkinson's disease due to PINK1 p.Q456X mutation--clinical and functional study.

BACKGROUND: Recessive mutations in the PTEN-induced putative kinase 1 (PINK1) gene cause early-onset Parkinson's disease (EOPD). The clinical phenotype of families that have this PINK1-associated disease may present with different symptoms, including typical PD. The loss of the PINK1 protein may lead to mitochondrial dysfunction, which causes dopaminergic neuron death. METHODS: The clinical phenotypes of a large Polish family with EOPD and an identified PINK1 homozygous nonsense mutation were assessed. Ubiquitination and degradation of mitochondrial parkin substrates as well as mitochondrial bioenergetics were investigated as direct functional readouts for PINK1's kinase activity in biopsied dermal fibroblasts. RESULTS: A four-generation family was genealogically evaluated. Genetic screening identified two affected subjects who were both homozygous carriers of the pathogenic PINK1 p.Q456X substitution. Both patients presented with dystonia and gait disorders at symptom onset. Seven heterozygous mutation carriers remained unaffected. Functional studies revealed that the PINK1 p.Q456X protein is non-functional in activating the downstream ubiquitin ligase parkin and priming the ubiquitination of its substrates, and that the RNA levels of PINK1 were significantly reduced. CONCLUSIONS: The PINK1 p.Q456X mutation leads to a decrease in mRNA and a loss of protein function. The foot dystonia and gait disorders seen at disease onset in affected members of our family, which were accompanied by parkinsonism had a similar clinical presentation to what has been described in previous reports of PINK1 mutation carriers.

Alpha-synuclein repeat variants and survival in Parkinson's disease.

OBJECTIVES: To determine whether α-synuclein dinucleotide repeat (REP1) genotypes are associated with survival in Parkinson's disease (PD). METHODS: Investigators from the Genetic Epidemiology of Parkinson's Disease Consortium provided REP1 genotypes and baseline and follow-up clinical data for cases. The primary outcome was time to death. Cox proportional hazards regression models were used to assess the association of REP1 genotypes with survival. RESULTS: Twenty-one sites contributed data for 6,154 cases. There was no significant association between α-synuclein REP1 genotypes and survival in PD. However, there was a significant association between REP1 genotypes and age at onset of PD (hazard ratio: 1.06; 95% confidence interval: 1.01-1.10; P value = 0.01). CONCLUSIONS: In our large consortium study, α-synuclein REP1 genotypes were not associated with survival in PD. Further studies of α-synuclein's role in disease progression and long-term outcomes are needed.

Protective effect of LRRK2 p.R1398H on risk of Parkinson's disease is independent of MAPT and SNCA variants.

The best validated susceptibility variants for Parkinson's disease are located in the α-synuclein (SNCA) and microtubule-associated protein tau (MAPT) genes. Recently, a protective p.N551K-R1398H-K1423K haplotype in the leucine-rich repeat kinase 2 (LRRK2) gene was identified, with p.R1398H appearing to be the most likely functional variant. To date, the consistency of the protective effect of LRRK2 p.R1398H across MAPT and SNCA variant genotypes has not been assessed. To address this, we examined 4 SNCA variants (rs181489, rs356219, rs11931074, and rs2583988), the MAPT H1-haplotype-defining variant rs1052553, and LRRK2 p.R1398H (rs7133914) in Caucasian (n = 10,322) and Asian (n = 2289) series. There was no evidence of an interaction of LRRK2 p.R1398H with MAPT or SNCA variants (all p ≥ 0.10); the protective effect of p.R1398H was observed at similar magnitude across MAPT and SNCA genotypes, and the risk effects of MAPT and SNCA variants were observed consistently for LRRK2 p.R1398H genotypes. Our results indicate that the association of LRRK2 p.R1398H with Parkinson's disease is independent of SNCA and MAPT variants, and vice versa, in Caucasian and Asian populations.

Agraphia in patients with frontotemporal dementia and parkinsonism linked to chromosome 17 with P301L MAPT mutation: dysexecutive, aphasic, apraxic or spatial phenomenon?

OBJECTIVES: Patients with frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) may be agraphic. The study aimed at characterizing agraphia in individuals with a P301L MAPT mutation. METHODS: Two pairs of siblings with FTDP-17 were longitudinally examined for agraphia in relation to language and cognitive deficits. RESULTS: All patients presented with dysexecutive agraphia. In addition, in the first pair of siblings one sibling demonstrated spatial agraphia with less pronounced allographic agraphia and the other sibling had aphasic agraphia. Aphasic agraphia was also present in one sibling from the second pair. CONCLUSION: Agraphia associated with FTDP-17 is very heterogeneous.

Novel A18T and pA29S substitutions in α-synuclein may be associated with sporadic Parkinson's disease.

OBJECTIVE: Mutations in the α-synuclein-encoding gene SNCA are considered as a rare cause of Parkinson's disease (PD). Our objective was to examine the frequency of the SNCA point mutations among PD patients of Polish origin. METHODS: Detection of the known SNCA point mutations A30P (c.88G>C), E46K (c.136G>A) and A53T (c.157A>T) was performed either using the Sequenom MassArray iPLEX platform or by direct sequencing of the SNCA exons 2 and 3. As the two novel substitutions A18T (c.52G>A) and A29S (c.85G>T) were identified, their frequency in a control population of Polish origin was assessed and in silico analysis performed to investigate the potential impact on protein structure and function. RESULTS: We did not observe the previously reported point mutations in the SNCA gene in our 629 PD patients; however, two novel potentially pathogenic substitutions A18T and A29S were identified. Each variant was observed in a single patient presenting with a typical late-onset sporadic PD phenotype. Although neither variant was observed in control subjects and in silico protein analysis predicts a damaging effect for A18T and pA29S substitutions, the lack of family history brings into question the true pathogenicity of these rare variants. CONCLUSIONS: Larger population based studies are needed to determine the pathogenicity of the A18T and A29S substitutions. Our findings highlight the possible role of rare variants contributing to disease risk and may support further screening of the SNCA gene in sporadic PD patients from different populations.

Population-specific frequencies for LRRK2 susceptibility variants in the Genetic Epidemiology of Parkinson's Disease (GEO-PD) Consortium.

BACKGROUND: Variants within the leucine-rich repeat kinase 2 gene are recognized as the most frequent genetic cause of Parkinson's disease. Leucine-rich repeat kinase 2 variation related to disease susceptibility displays many features that reflect the nature of complex, late-onset sporadic disorders like Parkinson's disease. METHODS: The Genetic Epidemiology of Parkinson's Disease Consortium recently performed the largest genetic association study for variants in the leucine-rich repeat kinase 2 gene across 23 different sites in 15 countries. RESULTS: Herein, we detail the allele frequencies for the novel risk factors (p.A419V and p.M1646T) and the protective haplotype (p.N551K-R1398H-K1423K) nominated in the original publication. Simple population allele frequencies not only can provide insight into the clinical relevance of specific variants but also can help genetically define patient groups. CONCLUSIONS: Establishing individual patient-based genomic susceptibility profiles that incorporate both risk factors and protective factors will determine future diagnostic and treatment strategies.

A multi-centre clinico-genetic analysis of the VPS35 gene in Parkinson disease indicates reduced penetrance for disease-associated variants.

BACKGROUND: Two recent studies identified a mutation (p.Asp620Asn) in the vacuolar protein sorting 35 gene as a cause for an autosomal dominant form of Parkinson disease . Although additional missense variants were described, their pathogenic role yet remains inconclusive. METHODS AND RESULTS: We performed the largest multi-center study to ascertain the frequency and pathogenicity of the reported vacuolar protein sorting 35 gene variants in more than 15,000 individuals worldwide. p.Asp620Asn was detected in 5 familial and 2 sporadic PD cases and not in healthy controls, p.Leu774Met in 6 cases and 1 control, p.Gly51Ser in 3 cases and 2 controls. Overall analyses did not reveal any significant increased risk for p.Leu774Met and p.Gly51Ser in our cohort. CONCLUSIONS: Our study apart from identifying the p.Asp620Asn variant in familial cases also identified it in idiopathic Parkinson disease cases, and thus provides genetic evidence for a role of p.Asp620Asn in Parkinson disease in different populations worldwide.

Creation of an open-access, mutation-defined fibroblast resource for neurological disease research.

Our understanding of the molecular mechanisms of many neurological disorders has been greatly enhanced by the discovery of mutations in genes linked to familial forms of these diseases. These have facilitated the generation of cell and animal models that can be used to understand the underlying molecular pathology. Recently, there has been a surge of interest in the use of patient-derived cells, due to the development of induced pluripotent stem cells and their subsequent differentiation into neurons and glia. Access to patient cell lines carrying the relevant mutations is a limiting factor for many centres wishing to pursue this research. We have therefore generated an open-access collection of fibroblast lines from patients carrying mutations linked to neurological disease. These cell lines have been deposited in the National Institute for Neurological Disorders and Stroke (NINDS) Repository at the Coriell Institute for Medical Research and can be requested by any research group for use in in vitro disease modelling. There are currently 71 mutation-defined cell lines available for request from a wide range of neurological disorders and this collection will be continually expanded. This represents a significant resource that will advance the use of patient cells as disease models by the scientific community.

Large-scale replication and heterogeneity in Parkinson disease genetic loci.

OBJECTIVE: Eleven genetic loci have reached genome-wide significance in a recent meta-analysis of genome-wide association studies in Parkinson disease (PD) based on populations of Caucasian descent. The extent to which these genetic effects are consistent across different populations is unknown. METHODS: Investigators from the Genetic Epidemiology of Parkinson's Disease Consortium were invited to participate in the study. A total of 11 SNPs were genotyped in 8,750 cases and 8,955 controls. Fixed as well as random effects models were used to provide the summary risk estimates for these variants. We evaluated between-study heterogeneity and heterogeneity between populations of different ancestry. RESULTS: In the overall analysis, single nucleotide polymorphisms (SNPs) in 9 loci showed significant associations with protective per-allele odds ratios of 0.78-0.87 (LAMP3, BST1, and MAPT) and susceptibility per-allele odds ratios of 1.14-1.43 (STK39, GAK, SNCA, LRRK2, SYT11, and HIP1R). For 5 of the 9 replicated SNPs there was nominally significant between-site heterogeneity in the effect sizes (I(2) estimates ranged from 39% to 48%). Subgroup analysis by ethnicity showed significantly stronger effects for the BST1 (rs11724635) in Asian vs Caucasian populations and similar effects for SNCA, LRRK2, LAMP3, HIP1R, and STK39 in Asian and Caucasian populations, while MAPT rs2942168 and SYT11 rs34372695 were monomorphic in the Asian population, highlighting the role of population-specific heterogeneity in PD. CONCLUSION: Our study allows insight to understand the distribution of newly identified genetic factors contributing to PD and shows that large-scale evaluation in diverse populations is important to understand the role of population-specific heterogeneity.

An evaluation of the impact of MAPT, SNCA and APOE on the burden of Alzheimer's and Lewy body pathology.

PURPOSE: The study investigates the effects of genetic factors on the pathology of Alzheimer's disease (AD) and Lewy body (LB) diseases, including Parkinson's disease and dementia with Lewy bodies. METHODS: A multicentre autopsy series (762 brain samples) with AD, LB or vascular pathology was examined. The effects of the tau gene (MAPT) H1 haplotype, the H1 specific SNP rs242557, APOE and the α-synuclein gene (SNCA) 3'UTR SNP rs356165 on the burden of AD and LB pathology were assessed. Neurofibrillary tangles (NFTs) were counted in four brain regions, senile plaques in five and LBs in four. Braak NFT stage, brain weight and presence of vascular pathology were also documented. RESULTS: MAPT H1 associated with lower counts of NFTs in the middle frontal (p<0.001) and inferior parietal (p=0.005) cortices, and also with lower counts of senile plaques in the motor cortex (p=0.001). Associations of MAPT H1 with increased LB counts in the middle frontal cortex (p=0.011) and inferior parietal cortex (p=0.033) were observed but were not significant after multiple testing adjustment. The APOE ε4 allele was strongly associated with overall Alzheimer type pathology (all p≤0.001). SNCA rs356165 and the MAPT H1 specific SNP rs242557 did not associate with AD or LB pathology. CONCLUSION: This study shows for the first time that MAPT H1 is associated with reduced Alzheimer type pathology which could have important implications for the understanding of disease mechanisms and their genetic determinants.

PARK2 variability in Polish Parkinson's disease patients--interaction with mitochondrial haplogroups.

AIMS AND OBJECTIVES: A new pathomechanism of Parkinson's disease (PD) involving regulation of mitochondrial functions was recently proposed. Parkin complexed with mitochondrial transcription factor A (TFAM) binds mtDNA and promotes mitochondrial biogenesis, which is abolished by PARK2 gene mutations. We have previously shown that mitochondrial haplogroups/clusters and TFAM common variation influenced PD risk. We investigate the role of PARK2 polymorphisms on PD risk and their interactions with mitochondrial haplogroups/clusters as well as with TFAM variability. METHODS: 104 early-onset PD patients (EOPD, age at onset ≤ 50 years) were screened for PARK2 coding sequence changes including gene dosage alterations. Three selected PARK2 polymorphisms (S167N, V380L, D394N) were genotyped in 326 PD patients and 315 controls using TaqMan allelic discrimination assay. RESULTS: PARK2 screen revealed two heterozygous changes in two EOPD patients: exon 2 deletion and one novel synonymous variation (c.999C > A, P333P). In association study no differences in genotype/allele frequencies of S167N, V380L, D394N were found between analyzed groups. Stratification by mitochondrial clusters revealed higher frequency of V380L G/G genotype and allele G in PD patients, within HV cluster (p = 0.040; p = 0.022, respectively). Moreover, interaction between genotypes G/G V380L of PARK2 and G/G rs2306604 of TFAM, within HV cluster was significant (OR 2.05; CI 1.04-4.04; p = 0.038). CONCLUSIONS: Our results indicate that co-occurrence of G/G V380L PARK2 and G/G rs2306604 TFAM on the prooxidative HV cluster background can contribute to PD risk. We confirm low PARK2 mutation frequency in Polish EOPD patients.

Loss of ability to work and ability to live independently in Parkinson's disease.

OBJECTIVE: Ability to work and live independently is of particular concern for patients with Parkinson's disease (PD). We studied a series of PD patients able to work or live independently at baseline, and evaluated potential risk factors for two separate outcomes: loss of ability to work and loss of ability to live independently. METHODS: The series comprised 495 PD patients followed prospectively. Ability to work and ability to live independently were based on clinical interview and examination. Cox regression models adjusted for age and disease duration were used to evaluate associations of baseline characteristics with loss of ability to work and loss of ability to live independently. RESULTS: Higher UPDRS dyskinesia score, UPDRS instability score, UPDRS total score, Hoehn and Yahr stage, and presence of intellectual impairment at baseline were all associated with increased risk of future loss of ability to work and loss of ability to live independently (P ≤ 0.0033). Five years after initial visit, for patients ≤70 years of age with a disease duration ≤4 years at initial visit, 88% were still able to work and 90% to live independently. These estimates worsened as age and disease duration at initial visit increased; for patients >70 years of age with a disease duration >4 years, estimates at 5 years were 43% able to work and 57% able to live independently. CONCLUSIONS: The information provided in this study can offer useful information for PD patients in preparing for future ability to perform activities of daily living.

Genetics of essential tremor.

Essential tremor (ET) is a prevalent condition manifesting with progressive action tremor. Although ET was traditionally viewed as a sporadic disease, a significant proportion of cases report a positive family history of tremor. Autosomal dominant inheritance can be demonstrated in many families. Previously, genome-wide linkage studies in families mapped three loci for ET, hereditary essential tremor-1 (ETM1), ETM2 and ETM3. However, no causal mutation has been replicated in candidate genes within these loci, including dopamine D3 receptor (DRD3) and HS1-binding protein 3 (HS1BP3). Recently, the first genome-wide association study in ET followed by replication studies conducted in diverse populations identified a significant association between the leucine-rich repeat and Ig domain containing 1 gene (LINGO1) SNP rs9652490 and risk for ET Although further novel variants were indentified in LINGO1 and its paralog LINGO2 that may be associated with risk for ET, the pathogenic mechanisms involved remain elusive. Given the possibility that ET as a complex trait may be influenced by the combined effects of rare variants, novel high-throughput technologies sequencing all exons across the genome (exome sequencing) or the whole genome (genome sequencing) may become crucial in understanding/deciphering the genetic background of ET.

Association of LRRK2 exonic variants with susceptibility to Parkinson's disease: a case-control study.

BACKGROUND: Background The leucine-rich repeat kinase 2 gene (LRRK2) harbours highly penetrant mutations that are linked to familial parkinsonism. However, the extent of its polymorphic variability in relation to risk of Parkinson's disease (PD) has not been assessed systematically. We therefore assessed the frequency of LRRK2 exonic variants in individuals with and without PD, to investigate the role of the variants in PD susceptibility. METHODS: LRRK2 was genotyped in patients with PD and controls from three series (white, Asian, and Arab-Berber) from sites participating in the Genetic Epidemiology of Parkinson's Disease Consortium. Genotyping was done for exonic variants of LRRK2 that were identified through searches of literature and the personal communications of consortium members. Associations with PD were assessed by use of logistic regression models. For variants that had a minor allele frequency of 0·5% or greater, single variant associations were assessed, whereas for rarer variants information was collapsed across variants. FINDINGS: 121 exonic LRRK2 variants were assessed in 15 540 individuals: 6995 white patients with PD and 5595 controls, 1376 Asian patients and 962 controls, and 240 Arab-Berber patients and 372 controls. After exclusion of carriers of known pathogenic mutations, new independent risk associations were identified for polymorphic variants in white individuals (M1646T, odds ratio 1·43, 95% CI 1·15-1·78; p=0·0012) and Asian individuals (A419V, 2·27, 1·35-3·83; p=0·0011). A protective haplotype (N551K-R1398H-K1423K) was noted at a frequency greater than 5% in the white and Asian series, with a similar finding in the Arab-Berber series (combined odds ratio 0·82, 0·72-0·94; p=0·0043). Of the two previously reported Asian risk variants, G2385R was associated with disease (1·73, 1·20-2·49; p=0·0026), but no association was noted for R1628P (0·62, 0·36-1·07; p=0·087). In the Arab-Berber series, Y2189C showed potential evidence of risk association with PD (4·48, 1·33-15·09; p=0·012). INTERPRETATION: The results for LRRK2 show that several rare and common genetic variants in the same gene can have independent effects on disease risk. LRRK2, and the pathway in which it functions, is important in the cause and pathogenesis of PD in a greater proportion of patients with this disease than previously believed. These results will help discriminate those patients who will benefit most from therapies targeted at LRRK2 pathogenic activity. FUNDING: Michael J Fox Foundation and National Institutes of Health.

Role of sepiapterin reductase gene at the PARK3 locus in Parkinson's disease.

Sepiapterin reductase (SPR) gene is an enzyme which catalyses the final step of tetrahydrobiopterin synthesis (BH4) and was implicated in Parkinson's disease (PD) pathogenesis as a candidate gene for PARK3 locus. A number of studies yielded association of the PARK3 locus with PD, and SPR knockout mice were shown to display parkinsonian features. To evaluate the role of SPR gene polymorphisms in diverse populations in PD, we performed collaborative analyses in the Genetic Epidemiology of Parkinson Disease (GEO-PD) Consortium. A total of 5 single nucleotide polymorphisms (3 in the promoter region and 2 in the 3' untranslated region [UTR]) were genotyped. Fixed as well as random effect models were used to provide summary risk estimates of SPR variants. A total of 19 sites provided data for 6547 cases and 9321 controls. Overall odds ratio estimates varied from 0.92 to 1.01. No overall association with the SPR gene using either fixed effect or random effect model was observed in the studied population. I(2) Metric varied from 0% to 36.2%. There was some evidence for an association for participants of North European/Scandinavian descent with the strongest signal for rs1876487 (odds ratio = 0.82; p value = 0.003). Interestingly, families which were used to map the PARK3 locus, have Scandinavian ancestry suggesting a founder effect. In conclusion, this large association study for the SPR gene revealed no association for PD worldwide. However, taking the initial mapping of the PARK3 into account, the role of a population-specific effect warrants consideration in future studies.

Human leukocyte antigen variation and Parkinson's disease.

A role for the immune system in the pathogenesis of Parkinson's Disease (PD) has previously been suggested. A recent genome-wide association (GWA) study identified an association between one single nucleotide polymorphism (SNP) in the human leucocyte antigen (HLA) region (HLA-DRA rs3129882) and PD in a population of American patients with European ancestry. In that study, the minor rs3129882 allele (G) was associated with an increased risk of PD under an additive model. Due to the increased likelihood of obtaining false positive results in GWA studies compared to studies conducted based on a hypothesis-driven approach, repeated validation of findings from GWA studies are necessary. Herein, we evaluated the association between rs3129882 and PD in three different Caucasian patient-control series (combined 1313 patients and 1305 controls) from the US, Ireland, and Poland. We observed no association (OR: 0.96, P = 0.50) between rs3129882 and PD when analyzing our data under an additive or dominant model. In contrast, when examined under a recessive model, the GG genotype was observed to be protective in the Irish (OR: 0.55, P = 0.008), Polish (OR: 0.67, P = 0.040) and combined (OR: 0.75, P = 0.006) patient-control series. In view of these diverging results, the exact role of genetic variation at the HLA region and susceptibility to PD remains to be resolved.

Independent and joint effects of the MAPT and SNCA genes in Parkinson disease.

OBJECTIVE: We studied the independent and joint effects of the genes encoding alpha-synuclein (SNCA) and microtubule-associated protein tau (MAPT) in Parkinson disease (PD) as part of a large meta-analysis of individual data from case-control studies participating in the Genetic Epidemiology of Parkinson's Disease (GEO-PD) consortium. METHODS: Participants of Caucasian ancestry were genotyped for a total of 4 SNCA (rs2583988, rs181489, rs356219, rs11931074) and 2 MAPT (rs1052553, rs242557) single nucleotide polymorphism (SNPs). Individual and joint effects of SNCA and MAPT SNPs were investigated using fixed- and random-effects logistic regression models. Interactions were studied on both a multiplicative and an additive scale, and using a case-control and case-only approach. RESULTS: Fifteen GEO-PD sites contributed a total of 5,302 cases and 4,161 controls. All 4 SNCA SNPs and the MAPT H1-haplotype-defining SNP (rs1052553) displayed a highly significant marginal association with PD at the significance level adjusted for multiple comparisons. For SNCA, the strongest associations were observed for SNPs located at the 3' end of the gene. There was no evidence of statistical interaction between any of the 4 SNCA SNPs and rs1052553 or rs242557, neither on the multiplicative nor on the additive scale. INTERPRETATION: This study confirms the association between PD and both SNCA SNPs and the H1 MAPT haplotype. It shows, based on a variety of approaches, that the joint action of variants in these 2 loci is consistent with independent effects of the genes without additional interacting effects.

A large-scale genetic association study to evaluate the contribution of Omi/HtrA2 (PARK13) to Parkinson's disease.

High-profile studies have provided conflicting results regarding the involvement of the Omi/HtrA2 gene in Parkinson's disease (PD) susceptibility. Therefore, we performed a large-scale analysis of the association of common Omi/HtrA2 variants in the Genetic Epidemiology of Parkinson's disease (GEO-PD) consortium. GEO-PD sites provided clinical and genetic data including affection status, gender, ethnicity, age at study, age at examination (all subjects); age at onset and family history of PD (patients). Genotyping was performed for the five most informative SNPs spanning the Omi/HtrA2 gene in approximately 2-3 kb intervals (rs10779958, rs2231250, rs72470544, rs1183739, rs2241028). Fixed as well as random effect models were used to provide summary risk estimates of Omi/HtrA2 variants. The 20 GEO-PD sites provided data for 6378 cases and 8880 controls. No overall significant associations for the five Omi/HtrA2 SNPs and PD were observed using either fixed effect or random effect models. The summary odds ratios ranged between 0.98 and 1.08 and the estimates of between-study heterogeneity were not large (non-significant Q statistics for all 5 SNPs; I(2) estimates 0-28%). Trends for association were seen for participants of Scandinavian descent for rs2241028 (OR 1.41, p=0.04) and for rs1183739 for age at examination (cut-off 65 years; OR 1.17, p=0.02), but these would not be significant after adjusting for multiple comparisons and their Bayes factors were only modest. This largest association study performed to define the role of any gene in the pathogenesis of Parkinson's disease revealed no overall strong association of Omi/HtrA2 variants with PD in populations worldwide.