Late-onset Parkinson's Disease Cases Research Articles

Association Analysis of Essential Tremor-Associated Genetic Variants in Sporadic Late-Onset Parkinson's Disease.

Parkinson's disease (PD) and Essential tremor (ET) are the two most common tremor diseases with recognized genetic pathogenesis. The overlapping clinical features suggest they may share genetic predispositions. Our previous study systematically investigated the association between rare coding variants in ET-associated genes and early-onset PD (EOPD), and found the suggestive association between teneurin transmembrane protein 4 (TENM4) and EOPD. In the current research, we explored the potential genetic interplay between ET-associated genetic loci/genes and sporadic late-onset PD (LOPD). We performed whole-genome sequencing in the 1962 sporadic LOPD cases and 1279 controls from mainland China. We first used logistic regression analysis to test the top 16 SNPs identified by the ET genome-wide association study for the association between ET and LOPD. Then we applied the optimized sequence kernel association testing to explore the rare variant burden of 33 ET-associated genes in this cohort. We did not observe a significant association between the included SNPs with LOPD. We also did not discover a significant burden of rare deleterious variants of ET-associated genes in association with LOPD risk. Our results do not support the role of ET-associated genetic loci and variants in LOPD. 1962 cases and 1279 controls were recruited to study the potential genetic interplay between ET-associated genetic loci/variants and sporadic LOPD.No significant association between the ET-associated SNPs and LOPD were observed.No significant burden of rare deleterious variants of ET-associated gene in LOPD risk were found.

Screening non-MAPT genes of the Chr17q21 H1 haplotype in Parkinson's disease

IntroductionThe microtubule-associated protein tau (MAPT) gene is considered a strong genetic risk factor for Parkinson's disease (PD) in Caucasians. MAPT is located within an inversion region of high linkage disequilibrium designated as H1 and H2 haplotype, and contains eight other genes which have been implicated in neurodegeneration. The aim of the current study was to identify common coding variants in strong linkage disequilibrium (LD) within the associated loci on chr17q21 harboring MAPT. MethodsSanger sequencing of coding exons in 90 Caucasian late-onset PD (LOPD) patients was performed. Specific gene sequencing for LRRC37A, LRRC37A2, ARL17A and ARL17B was not possible given the high homology, presence of pseudogenes and copy number variants that are in the region, and therefore four genes (NSF, KANSL1, SPPL2C, and CRHR1) were included in the analysis. Coding variants from these four genes that did not perfectly tag (r2 = 1) the MAPT H1/H2 haplotype were genotyped in an independent replication series of Caucasian PD cases (N = 851) and controls (N = 730). ResultsIn the 90 LOPD cases we identified 30 coding variants. Eleven non-synonymous variants tagged the MAPT H1/H2 haplotype, including two SPPL2C variants (rs12185233 and rs12373123) that had high pathogenic combined annotation dependent depletion (CADD) scores of >20. In the replication series, the non-synonymous KANSL1 rs17585974 variant was in very strong LD with MAPT H1/H2 and had a high CADD score of 24.7. ConclusionWe have identified several non-synonymous variants across neighboring genes of MAPT that may warrant further genetic and functional investigation within the biological etiology of PD.

The functional roles of retromer in Parkinson's disease.

The endosomal system is critical for the maintenance of intracellular homeostasis, and defects in this system are often linked to neurological disorders. The retromer complex is a critical coordinator of endosomal dynamics and has functional roles in multiple cellular processes through sorting cargoes from endosomes to the trans-Golgi network (TGN) or to the plasma membrane. Mammalian retromer comprises a core Vps26-Vps35-Vps29 trimer and associates with a range of proteins to generate endosomal tubular-vesicular carriers. Alterations in retromer function or its molecular organization have been a rising risk factor for Parkinson's disease (PD). Although genetic evidence has shown several variants within retromer in late-onset PD cases, the exact molecular machineries by which retromer variants induce the development of PD are still not completely elucidated. In this Review, we will focus on the functional roles of retromer in neuronal health, summarize advances in defining the cellular pathological phenotype caused by retromer deficiency or PD-linked retromer variants and discuss the potential clues of how retromer deregulation may contribute to PD pathogenesis.

Early-onset vs. Late-onset Parkinson's disease: A Clinical-pathological Study.

Several studies have compared early-onset Parkinson disease (EOPD) and late-onset Parkinson disease (LOPD) but most are not based on autopsy confirmed cases. We compared clinical and pharmacological profiles, time to reach irreversible Hoehn and Yahr (H&Y) Stage 3 and levodopa motor complications in autopsy confirmed EOPD and LOPD cases. At first clinic visit EOPD cases were younger but had longer disease duration and they died at a younger age (all p<0.0001). Anti-Parkinsonian drug use, including levodopa, was significantly delayed in EOPD. Lifetime use of amantadine (p<0.05) and dopamine agonists (p<0.01) were higher in EOPD. While lifetime use of levodopa was similar in the two groups, levodopa was used for a significantly longer period by EOPD (p< 0.0001). EOPD had a higher cumulative incidence of dyskinesias (p<0.01), wearing-off (p<0.01), and on-off (p<0.01). However, the time to dyskinesia onset was similar in the two groups. The threshold to wearing-off was much longer in EOPD (p<0.01). H&Y stage profile at first visit was similar in the two groups. The duration from disease onset to reach irreversible H&Y stage 3 was significantly longer in EOPD. Our observations indicate that progression of PD is slower in EOPD and suggest that the pre-clinical interval in this group is longer. These findings can be used for case selection for drug trials and studies of the pathogenesis of PD.

Analysis of non-synonymous-coding variants of Parkinson's disease-related pathogenic and susceptibility genes in East Asian populations

To evaluate the contribution of non-synonymous-coding variants of known familial and genome-wide association studies (GWAS)-linked genes for Parkinson's disease (PD) to PD risk in the East Asian population, we sequenced all the coding exons of 39 PD-related disease genes and evaluated the accumulation of rare non-synonymous-coding variants in 375 early-onset PD cases and 399 controls. We also genotyped 782 non-synonymous-coding variants of these genes in 710 late-onset PD cases and 9046 population controls. Significant enrichment of LRRK2 variants was observed in both early- and late-onset PD (odds ratio = 1.58; 95% confidence interval = 1.29-1.93; P = 8.05 × 10(-6)). Moderate enrichment was also observed in FGF20, MCCC1, GBA and ITGA8. Half of the rare variants anticipated to cause loss of function of these genes were present in healthy controls. Overall, non-synonymous-coding variants of known familial and GWAS-linked genes appear to make a limited contribution to PD risk, suggesting that clinical sequencing of these genes will provide limited information for risk prediction and molecular diagnosis.

Mutational analysis of the VCP gene in Parkinson's disease

Mutations in the valosin-containing protein gene (VCP) have been identified in neurological disorders (inclusion body myopathy--early Paget's disease of the bone--frontotemporal dementia and amyotrophic lateral sclerosis) and are thought to play a role in the clearance of abnormally folded proteins. Parkinsonism has been noted in kindreds with VCP mutations. Based on this, we hypothesized that mutations in VCP may also contribute to idiopathic Parkinson's disease (PD). We screened the coding region of the VCP gene in a large cohort of 768 late-onset PD cases (average age at onset, 70 years), both sporadic and with positive family history. We identified a number of rare single nucleotide changes, including a variant previously described to be pathogenic, but no clear disease-causing variants. We conclude that mutations in VCP are not a common cause for idiopathic PD.

Intrafamilial variability of Parkinson phenotype in SCAs: Novel cases due to SCA2 and SCA3 expansions

Background Parkinson's disease (PD) has been related to mutations associated with spinocerebellar ataxias (SCA); the frequency of the diagnosis of these mutations is low in general late-onset PD cases. Our aim was to investigate a selected high-risk group of PD patients. Methods PD patients with autosomal dominant inheritance or atypical neurological manifestations were enrolled, underwent a full neurological examination and had the CAG tracts of their SCA1, 2, 3, 6 and 7 genes analyzed. Results Of the 23 studied families, two SCA3 and one SCA2 cases were identified. All had autosomal dominant inheritance. In the SCA2 pedigree, four affected sibs had a homogeneous PD phenotype. CAG repeats varied between 35 and 44 with CAA interruptions. Intrafamilial phenotypic heterogeneity was identified in the SCA3 pedigrees; parkinsonian and ataxic phenotypes coexisted in both kindreds. CAGn varied between 69 and 71 repeats. Age of onset was lower in the SCA3 patients than in the remaining 24 cases (38 versus 46.7 ± 12 years of age, p = 0.003). Conclusions SCA2 and SCA3 mutations were detected in 13% of the present sample: the strategy of selecting a high-risk group increased the rate of making these diagnoses. The SCA2 cases confirmed an association between PD and interrupted expansions, as well as PD intrafamilial phenotypic homogeneity. Clinical heterogeneity of SCA3 pedigrees suggests that disease-modifying agents outside the MJD1 gene may play a role in determining PD symptoms in this disorder.

Analysis of 14 LRRK2 mutations in Parkinson's plus syndromes and late‐onset Parkinson's disease

The pleomorphic pathology of postmortem LRRK2-positive patients and the frequent association with late-onset Parkinson's disease (LOPD) symptoms suggest that LRRK2 mutations may play a role in Parkinson's Plus disorders and LOPD. Published studies primarily focus on the common G2019S mutation. Analysis of a spectrum of LRRK2 mutations in Parkinson's Plus disorders has yet to be reported. We investigated 14 leucine-rich repeat kinase 2 (LRRK2) mutations in a cohort of Parkinson's Plus disorders and LOPD. A total of 458 patients with progressive supranuclear palsy (PSP), multiple system atrophy (MSA), corticobasal ganglionic degeneration (CBGD), atypical Parkinsonism (AP), and LOPD were screened for 14 mutations that span exons 19 to 41 of the LRRK2 gene. Among the LOPD cases, 1 patient was found to harbor the R1441C mutation. He presented with typical features of PD at age of 58 years old and responded well to levodopa. We did not detect any of the 14 mutations in PSP, MSA, CBGD, and AP patients. We highlight the first case of LRRK2 R1441C mutation in late onset sporadic PD of non-European ancestry. Furthermore, extensive mutational screen found LRRK2 mutations to be rare among patients who presented with PSP, MSA, CBGD, and AP.

Evidence for novel loci for late-onset Parkinson’s disease in a genetic isolate from the Netherlands

We studied patients with idiopathic Parkinson's disease (PD) from an isolated population in the Netherlands aiming to map gene(s) involved in PD susceptibility. A total of 109 parkinsonism patients were independently ascertained, of whom 62 presented late-onset, idiopathic PD. Genealogical research showed that 45 index cases with idiopathic PD were linked to a common ancestor, indicating familiar clustering among the patients. This strong familial clustering was highly significant (P = 0.005) when compared to random controls from the same population. We performed a genome wide scan using 382 polymorphic markers in 44 distantly related PD patients plus 112 unaffected first-degree relatives and spouses. Our genome wide association analysis (DISLAMB) revealed evidence of association at a nominal P-value < 0.01 for markers D2S2333, D4S405, D9S158, D13S153. Other regions on chromosomes 3p, 4q, 14q, 17p and 17q were found at a significance level of P < 0.05. In a follow-up study, we investigated all the positive regions using a denser marker set and a larger sample (total of 630 individuals including all late-onset PD patients). The strongest evidence for association remained for the 9q and 14q region. A significant association was found for marker D9S1838 (OR = 2.0, 95% CI 1.1-3.5, P = 0.014) and D14S65 (OR = 3.2, 95% CI 1.7-6.1, P < 0.001). Moreover, a common haplotype with excess of sharing among late-onset PD cases was observed on both regions. Our results suggest the existence of two loci influencing PD susceptibility on chromosome 9q and 14q.

Identification of a Novel LRRK2 Mutation Linked to Autosomal Dominant Parkinsonism: Evidence of a Common Founder across European Populations

Autosomal dominant parkinsonism has been attributed to pathogenic amino acid substitutions in leucine-rich repeat kinase 2 (LRRK2). By sequencing multiplex families consistent with a PARK8 assignment, we identified a novel heterozygous LRRK2 mutation. A referral sample of 248 affected probands from families with autosomal dominant parkinsonism was subsequently assessed; 7 (2.8%) were found to carry a heterozygous LRRK2 6055G-->A transition (G2019S). These seven patients originate from the United States, Norway, Ireland, and Poland. In samples of patients with idiopathic Parkinson disease (PD) from the same populations, further screening identified six more patients with LRRK2 G2019S; no mutations were found in matched control individuals. Subsequently, 42 family members of the 13 probands were examined; 22 have an LRRK2 G2019S substitution, 7 with a diagnosis of PD. Of note, all patients share an ancestral haplotype indicative of a common founder, and, within families, LRRK2 G2019S segregates with disease (multipoint LOD score 2.41). Penetrance is age dependent, increasing from 17% at age 50 years to 85% at age 70 years. In summary, our study demonstrates that LRRK2 G2019S accounts for parkinsonism in several families within Europe and North America. Our work highlights the fact that a proportion of clinically typical, late-onset PD cases have a genetic basis.