Sporadic Early-onset Parkinson's Disease Research Articles

Genetic analysis of transcription factors in dopaminergic neuronal development in Parkinson's disease.

Genetic variants of dopaminergic transcription factor-encoding genes are suggested to be Parkinson's disease (PD) risk factors; however, no comprehensive analyses of these genes in patients with PD have been undertaken. Therefore, we aimed to genetically analyze 16 dopaminergic transcription factor genes in Chinese patients with PD. Whole-exome sequencing (WES) was performed using a Chinese cohort comprising 1917 unrelated patients with familial or sporadic early-onset PD and 1652 controls. Additionally, whole-genome sequencing (WGS) was performed using another Chinese cohort comprising 1962 unrelated patients with sporadic late-onset PD and 1279 controls. We detected 308 rare and 208 rare protein-altering variants in the WES and WGS cohorts, respectively. Gene-based association analyses of rare variants suggested that MSX1 is enriched in sporadic late-onset PD. However, the significance did not pass the Bonferroni correction. Meanwhile, 72 and 1730 common variants were found in the WES and WGS cohorts, respectively. Unfortunately, single-variant logistic association analyses did not identify significant associations between common variants and PD. Variants of 16 typical dopaminergic transcription factors might not be major genetic risk factors for PD in Chinese patients. However, we highlight the complexity of PD and the need for extensive research elucidating its etiology.

Genetic analysis of dystonia-related genes in Parkinson's disease.

Parkinson's disease (PD) and dystonia are two closely related movement disorders with overlaps in clinical phenotype. Variants in several dystonia-related genes were demonstrated to be associated with PD; however, genetic evidence for the involvement of dystonia-related genes in PD has not been fully studied. Here, we comprehensively investigated the association between rare variants in dystonia-related genes and PD in a large Chinese cohort. We comprehensively analyzed the rare variants of 47 known dystonia-related genes by mining the whole-exome sequencing (WES) and whole-genome sequencing (WGS) data from 3,959 PD patients and 2,931 healthy controls. We initially identified potentially pathogenic variants of dystonia-related genes in patients with PD based on different inheritance models. Sequence kernel association tests were conducted in the next step to detect the association between the burden of rare variants and the risk for PD. We found that five patients with PD carried potentially pathogenic biallelic variants in recessive dystonia-related genes including COL6A3 and TH. Additionally, we identified 180 deleterious variants in dominant dystonia-related genes based on computational pathogenicity predictions and four of which were considered as potentially pathogenic variants (p.W591X and p.G820S in ANO3, p.R678H in ADCY5, and p.R458Q in SLC2A1). A gene-based burden analysis revealed the increased burden of variant subgroups of TH, SQSTM1, THAP1, and ADCY5 in sporadic early-onset PD, whereas COL6A3 was associated with sporadic late-onset PD. However, none of them reached statistical significance after the Bonferroni correction. Our findings indicated that rare variants in several dystonia-related genes are suggestively associated with PD, and taken together, the role of COL6A3 and TH genes in PD is highlighted.

The mutation spectrum of Parkinson‐disease‐related genes in early‐onset Parkinson's disease in ethnic Chinese

Recent genetic progress has shown many causative/risk genes linked to Parkinson's disease (PD), mainly in patients of European ancestry. The study aimed to investigate the PD-related genes and determine the mutational spectrum of early-onset PD in ethnic Chinese. In this study, whole-exome sequencing and/or gene dosage analysis were performed in 704 early-onset PD (EOPD) patients (onset age ≤45 years) and 1866 controls. Twenty-six PD-related genes and 20 other genes linked to neurodegenerative and lysosome diseases were analysed. Eighty-two (11.6%, 82/704) EOPD patients carrying rare pathogenic/likely pathogenic variants in PD-related genes were identified. The mutation frequency in autosomal recessive inheritance EOPD (42.9%, 27/63) was much higher than that in autosomal dominant inheritance EOPD (0.9%, 12/110) or sporadic EOPD (8.1%, 43/531). Bi-allelic mutations in PRKN were the most frequent, accounting for 5.1% of EOPD cases. Three common pathogenic variants, p.A53V in SNCA, p.G284R in PRKN and p.P53Afs*38 in CHCHD2, occur exclusively in Asians. The putative damaging variants from GBA, PRKN, DJ1, PLA2G6 and GCH1 contributed to the collective risk for EOPD. Notably, the protein-truncating variants in CHCHD2 were enriched in EOPD, especially for p.P53Afs*38, which was also found in three patients from an independent cohort of patients with late-onset PD (n=1300). Functional experiments confirmed that truncated CHCHD2 variants cause loss of function and are linked to mitochondrial dysfunction. Our study reveals that the genetic spectrum of EOPD in Chinese, which may help develop genetic scanning strategies, provided more evidence supporting CHCHD2 in PD.

Parkin is the most common causative gene in a cohort of mainland Chinese patients with sporadic early-onset Parkinson's disease.

IntroductionGenetic mutations associated with early‐onset Parkinson's disease (EOPD) vary widely among different ethnicities. We detected the genes associated with EOPD in a Chinese cohort using next‐generation sequencing (NGS) combined with multiplex ligation‐dependent probe amplification (MLPA) and analyzed the phenotypic characteristics of the mutation carriers.MethodsCohort of 23 sporadic EOPD patients (onset age ≤ 45 years) were recruited. Genetic causes were identified by a targeted NGS panel containing 136 known extrapyramidal disease‐causative genes. Multiplications or deletions of PD‐causing genes were detected using the MLPA method. Demographic and clinical data were obtained, analyzed, and compared between patients with and those without Parkin gene variants.ResultsWe identified 14 pathogenic or likely pathogenic variants (12 in Parkin, 1 in LRRK2, and 1 in VPS13C) in 10 patients (43.5%) and 8 rare variants of uncertain significance in 9 patients (39.1%). Parkin (34.8%) was the most common causative gene among our patients cohort, and exon deletion (62.5%) was the main type of variant. Patients with Parkin mutations had a younger age of onset, longer delay in diagnosis, slower disease progression, higher frequency of hyperreflexia, fatigue, and less hyposmia compared to patients without Parkin mutations.ConclusionOur results revealed a higher prevalence of Parkin mutations in Chinese sporadic EOPD patients, and notably, exon deletion was the most common type of mutation. EOPD patients with Parkin mutations showed unique clinical characteristics.

The role of genetics in Parkinson's disease: a large cohort study in Chinese mainland population.

This study aimed to determine the mutational spectrum of familial Parkinson's disease and sporadic early-onset Parkinson's disease (sEOPD) in a mainland Chinese population and the clinical features of mutation carriers. We performed multiplex ligation-dependent probe amplification assays and whole-exome sequencing for 1676 unrelated patients with Parkinson's disease in a mainland Chinese population, including 192 probands from families with autosomal-recessive Parkinson's disease, 242 probands from families with autosomal-dominant Parkinson's disease, and 1242 sEOPD patients (age at onset ≤ 50). According to standards and guidelines from the American College of Medical Genetics and Genomics, pathogenic/likely pathogenic variants in 23 known Parkinson's disease-associated genes occurred more frequently in the autosomal-recessive Parkinson's disease cohort (65 of 192, 33.85%) than in the autosomal-dominant Parkinson's disease cohort (10 of 242, 4.13%) and the sEOPD cohort (57 of 1242, 4.59%), which leads to an overall molecular diagnostic yield of 7.88% (132 of 1676). We found that PRKN was the most frequently mutated gene (n = 83, 4.95%) and present the first evidence of an SNCA duplication and LRRK2 p.N1437D variant in mainland China. In addition, several novel pathogenic/likely pathogenic variants including LRRK2 (p.V1447M and p.Y1645S), ATP13A2 (p.R735X and p.A819D), FBXO7 (p.G67E), LRP10 (c.322dupC/p.G109Rfs*51) and TMEM230 (c.429delT/p.P144Qfs*2) were identified in our cohort. Furthermore, the age at onset of the 132 probands with genetic diagnoses (median, 31.5 years) was about 14.5 years earlier than that of patients without molecular diagnoses (i.e. non-carriers, median 46.0 years). Specifically, the age at onset of Parkinson's disease patients with pathogenic/likely pathogenic variants in ATP13A2, PLA2G6, PRKN, or PINK1 was significantly lower than that of non-carriers, while the age at onset of carriers with other gene pathogenic/likely pathogenic variants was similar to that of non-carriers. The clinical spectrum of Parkinson's disease-associated gene carriers in this mainland Chinese population was similar to that of other populations. We also detected 61 probands with GBA possibly pathogenic variants (3.64%) and 59 probands with GBA p.L444P (3.52%). These results shed insight into the genetic spectrum and clinical manifestations of Parkinson's disease in mainland China and expand the existing repertoire of pathogenic or likely pathogenic variants involved in known Parkinson's disease-associated genes. Our data highlight the importance of genetic testing in Parkinson's disease patients with age at onset < 40 years, especially in those from families with a recessive inheritance pattern, who may benefit from early diagnosis and treatment.

Diagnostic exome sequencing in early-onset Parkinson's disease confirms VPS13C as a rare cause of autosomal-recessive Parkinson's disease.

Parkinson's disease (PD) is a genetically heterogeneous disorder and new putative disease genes are discovered constantly. Therefore, whole-exome sequencing could be an efficient approach to genetic testing in PD. To evaluate its performance in early-onset sporadic PD, we performed diagnostic exome sequencing in 80 individuals with manifestation of PD symptoms at age 40 or earlier and a negative family history of PD. Variants in validated and candidate disease genes and risk factors for PD and atypical Parkinson syndromes were annotated, followed by further analysis for selected variants. We detected pathogenic variants in Mendelian genes in 6.25% of cases and high-impact risk factor variants in GBA in 5% of cases, resulting in overall maximum diagnostic yield of 11.25%. One individual was compound heterozygous for variants affecting canonical splice sites in VPS13C, confirming the causal role of protein-truncating variants in this gene linked to autosomal-recessive early-onset PD. Despite the low diagnostic yield of exome sequencing in sporadic early-onset PD, the confirmation of the recently discovered VPS13C gene highlights its advantage over using predefined gene panels.

Analysis of the genetic variability in Parkinson's disease from Southern Spain

To date, a large spectrum of genetic variants has been related to familial and sporadic Parkinson's disease (PD) in diverse populations worldwide. However, very little is known about the genetic landscape of PD in Southern Spain, despite its particular genetic landscape coming from multiple historical migrations. We included 134 PD patients in this study, of which 97 individuals were diagnosed with late-onset sporadic PD (LOPD), 28 with early-onset sporadic PD (EOPD), and 9 with familial PD (FPD). Genetic analysis was performed through a next-generation sequencing panel to screen 8 PD-related genes (LRRK2, SNCA, PARKIN, PINK1, DJ-1, VPS35, GBA, and GCH1) in EOPD and FPD groups and direct Sanger sequencing of GBA exons 8–11 and LRRK2 exons 31 and 41 in the LOPD group. In the EOPD and FPD groups, we identified 11 known pathogenic mutations among 15 patients (40.5 %). GBA (E326K, N370S, D409H, L444P) mutations were identified in 7 patients (18.9 %); LRRK2 (p.R1441G and p.G2019S) in 3 patients (8.1 %); biallelic PARK2 mutations (p.N52fs, p.V56E, p.C212Y) in 4 cases (10.8%) and PINK1 homozygous p.G309D in 1 patient (2.7 %). An EOPD patient carried a single PARK2 heterozygous mutation (p.R402C), and another had a novel heterozygous mutation in VPS35 (p.R32S), both of unknown significance. Moreover, pathogenic mutations in GBA (E326K, T369M, N370S, D409H, L444P) and LRRK2 (p.R1441G and p.G2019S) were identified in 13 patients (13.4 %) and 4 patients (4.1 %), respectively, in the LOPD group. A large number of known pathogenic mutations related to PD have been identified. In particular, GBA and LRRK2 mutations appear to be considerably frequent in our population, suggesting a strong Jewish influence. Further research is needed to study the contribution of the novel found mutation p.R32S in VPS35 to the pathogenesis of PD.

A systematic screening to identify de novo mutations causing sporadic early-onset Parkinson's disease.

Despite the many advances in our understanding of the genetic basis of Mendelian forms of Parkinson's disease (PD), a large number of early-onset cases still remain to be explained. Many of these cases, present with a form of disease that is identical to that underlined by genetic causes, but do not have mutations in any of the currently known disease-causing genes. Here, we hypothesized that de novo mutations may account for a proportion of these early-onset, sporadic cases. We performed exome sequencing in full parent–child trios where the proband presents with typical PD to unequivocally identify de novo mutations. This approach allows us to test all genes in the genome in an unbiased manner. We have identified and confirmed 20 coding de novo mutations in 21 trios. We have used publicly available population genetic data to compare variant frequencies and our independent in-house dataset of exome sequencing in PD (with over 1200 cases) to identify additional variants in the same genes. Of the genes identified to carry de novo mutations, PTEN, VAPB and ASNA1 are supported by various sources of data to be involved in PD. We show that these genes are reported to be within a protein–protein interaction network with PD genes and that they contain additional rare, case-specific, mutations in our independent cohort of PD cases. Our results support the involvement of these three genes in PD and suggest that testing for de novo mutations in sporadic disease may aid in the identification of novel disease-causing genes.

Analysis of PLA2G6 gene mutation in sporadic early-onset parkinsonism patients from Chinese population

Recent studies have shown that PLA2G6 is a causative gene for PARK14-linked autosomal recessive early-onset complicated dystonia-parkinsonism, early-onset parkinsonism with frontotemporal dementia and autosomal recessive early-onset Parkinsonism without added complicated clinical features. In order to investigate the characteristics of PLA2G6 gene mutations in Chinese sporadic early-onset parkinsonism (EOP) patients, we performed polymerase chain reaction and DNA direct sequencing on a cohort of sporadic EOP patients from Chinese population. In this study, we found a novel heterozygous varient (p.G679V). Bioinformatics demonstrates that p.G679V exhibits highly conserved residues across species, which hints it might be a pathogenic mutation. Our result indicated that PLA2G6 mutations might not be a main cause of Chinese sporadic EOP.

Mutation analysis of PINK1 gene in patients with early-onset Parkinsonism.

To determine the frequency of mutations in PINK1 in Chinese Han people with sporadic early-onset Parkinsonism (EOP). DNA sequencing was used to detect point mutations and small deletions/insertions, and quantitative real-time PCR was carried out to detect deletions/insertions and rearrangements in 149 patients and 150 healthy controls. Four heterozygous mutations in PINK1 were identified, including 3 missense mutations (c.832C>G, c. 938C>T, c.1 220G>A) and ex 3-8 del. A novel single nucleotide polymorphism (SNP) c.899+18G>A and 14 reported SNPs were identified. Chi-square test showed that c.189C> T and c.960-5G>A had significant difference in the genotype frequencies and allele frequencies between the patients and the controls (for c.189C>T genotype χ(2)=21.244,P<0.0001; T allele χ(2)=24.353,P<0.0001, and for c.960-5G>A genotype's χ(2)=6.524,P =0.038; A allele χ(2)=6.725,P=0.0095). About 3.35% Chinese Han patients with EOP carry mutations in PINK1. Two SNPs c.189C>T and c.960-5G>A may contribute to the risk of EOP in Chinese Han people.

Parkin dosage mutations in patients with early-onset sporadic and familial Parkinson's disease in Chinese: An independent pathogenic role

Mutations in the parkin gene have been identified as one of the important genetic factors for the etiology of PD. However, pathogenicities of parkin mutations, especially of those heterozygotes, remain controversial, possibly due to confusions caused by the “mixed” effects of all types of mutations. Here we report a study on the independent effects of exonic deletions/duplications (or dosage mutations) on the risk for and clinical profiles of PD in a Chinese cohort consisting of 29 autosomal-recessive early-onset parkinsonism (AREP) families and 173 patients with sporadic early-onset Parkinson's disease (EOPD). Detected simultaneously by multiplex PCR/denaturing high-performance liquid chromatography and real-time quantitative PCR analysis, heterozygous or homozygous dosage mutations were identified in exons 2–7 of parkin. The overall frequency of these mutations for both types of EOPD patients (8.91%, 18/202) was significantly higher than that of the controls (0%, 0/54) (p=0.03), and heterozygous mutations were more frequent in the AREP probands (17.2%, 5/29) than in the controls (0%) (p=0.004) and the sporadic EOPD cases (3.5%, 6/173) (p=0.01). AREP patients with dosage mutations had significantly younger age at onset (AAO) (p=0.000) and were more likely to present as bradykinesia and complicated with dystonia or dyskinesia compared with those without mutations. Sporadic EOPD patients with dosage mutations do not have an earlier AAO but are more likely to present as tremor and bradykinesia. These data suggested that dosage mutations alone can increase the risk for both sporadic and familial EOPD and affect their clinical aspects, but might contribute to a greater degree to familial EOPD.

Mutation analysis of Parkin, PINK1 and DJ-1 genes in Chinese patients with sporadic early onset parkinsonism

Early onset parkinsonism (EOP) has been associated with mutations in the Parkin, PINK1, and DJ-1 genes. We studied the prevalence of mutations in all three genes in 127 unrelated Chinese patients with apparently sporadic EOP using direct sequencing analysis and real-time quantitative PCR analysis assay. There are 16 patients (12.6%) with mutations of Parkin gene, four patients (3.1%) with mutations of PINK1 gene, and three patients (2.4%) with mutation of DJ-1 gene. In conclusion, Parkin gene mutation is the most common pathogenic factor in Chinese patients with sporadic EOP. Mutations of DJ-1 and PINK1 gene are also found in Chinese patients with sporadic EOP.

PINK1 mutations in a Brazilian cohort of early‐onset Parkinson's disease patients

Data on the frequency of PINK1 mutations in Brazilian patients with early-onset Parkinson's disease (EOPD) are lacking. The aim of this report was to investigate mutations of the PINK1 gene in a cohort of Brazilian patients with EOPD. Sixty consecutive familial or sporadic EOPD patients were included. All eight PINK1 exons and exon-intron boundaries were analyzed. We did not find any pathogenic mutation of PINK1 in our cohort. Single Nucleotide Polymorphisms (SNP) were identified in 46.7% of the patients and in 45.9% of controls (P = 0.9). The SNPs identified in our patients had already been described in previous reports. The results of our study support the hypothesis that mutations in PINK1 may not be a relevant cause of EOPD. In Brazil, if we consider only EOPD patients, it seems that parkin and LRRK2 mutations are more common.

Genotypic and phenotypic characteristics of Dutch patients with early onset Parkinson's disease

Early onset Parkinson's disease (EOPD) has been associated with mutations in the Parkin, DJ-1, PINK1, LRRK2, and SNCA genes. The aim of this study is to assess the contribution of these genes in a Dutch EOPD cohort and the phenotypic characteristics of the mutation carriers. A total of 187 unrelated Dutch EOPD patients (age at onset < or = 50 years) were phenotyped and screened for mutations in all exons of Parkin, DJ-1, and PINK1 by direct sequencing and gene dosage analysis. Additionally, analysis of the A30P mutation and exon dosage of SNCA and sequencing of exons 19,31,35,38,41, and 48 of LRRK2 was performed. Pathogenic variations could explain disease in 4% (7 of 187) of the patients including five patients carrying homozygous or compound heterozygous mutations in Parkin, one with a novel homozygous deletion in DJ-1 (P158Del) and one with a heterozygous mutation in LRRK2 (T2356I). We found seven novel mutations. The phenotypic characteristics of mutation carriers varied widely, comparable to the variability seen in sporadic EOPD. Parkin is the most frequently mutated gene in this EOPD cohort, followed by DJ-1, PINK1 and LRRK2. The low overall mutation frequency indicates that the extrapolation of mutation frequencies from other populations should be applied with caution.

α-Synuclein gene duplication is present in sporadic Parkinson disease

Ahn et al.1 reported that α-synuclein gene ( SNCA ) multiplications were present in 2/878 patients with sporadic Parkinson disease (PD), a frequency of approximately 0.2%. Previous investigations of SNCA mutations were performed primarily in PD families with autosomal dominant inheritance.2–5 We searched for SNCA multiplications in 101 patients with early onset sporadic PD, mostly of European (84%) and North African (4%) origin. The molecular analysis was performed with the SALSA MLPA kit P051 (MRC Holland, Amsterdam, the Netherlands), as recommended by the supplier. Peak areas representing exons 1, 3–6 of SNCA (figure e-1, A, on the Neurology ® Web site at www.neurology.org) were approximately 1.5 times larger in one of the patients (1%) compared to the control, suggesting that the entire SNCA gene was duplicated. This was …

LRRK2emph Exon 41 Mutations in Sporadic Parkinson Disease in Europeans

Mutations in leucine-rich repeat kinase 2 gene (LRRK2), particularly the G2019S mutation in exon 41, have been detected in familial and sporadic Parkinson disease (PD) cases. To assess the frequency of LRRK2 exon 41 mutations in a series of sporadic PD cases from Europe and to determine the clinical features of LRRK2 mutation carriers. We analyzed European cases of sporadic PD for the presence of LRRK2 exon 41 mutations. These mutations were screened by denaturing high-performance liquid chromatography, and abnormal chromatograph traces were investigated by direct sequencing to determine the exact nature of the variants. Early-onset sporadic PD cases were also screened for parkin mutations. The haplotypes associated with the G2019S mutation were determined. The clinical characteristics of patients carrying LRRK2 mutations were detailed. French Network for the Study of Parkinson Disease Genetics. Patients Three hundred twenty patients with apparently sporadic PD from Europe. Results of genetic analyses. We found the G2019S mutation in 6 patients and identified 2 new variants (Y2006H and T2031S) in 1 patient each. Their clinical features were similar to those of typical PD. All G2019S mutation carriers shared a common haplotype. The G2019S mutation is almost as frequent in sporadic cases (1.9%) as in previously reported familial cases (2.9%) in Europe and occurs in the same common founder. We identified 2 novel variants. Although the phenotype of LRRK2 mutation carriers closely resembles that of typical PD, the age at onset was younger (29 years in 1 patient) than previously described, and 3 patients were improved by deep brain stimulation.

A common A340T variant in PINK1 gene associated with late-onset Parkinson's disease in Chinese

Parkinson's disease (PD) is a complex neurodegenerative disease with genetic risk factors. Common variants in genes implicated in hereditary forms of parkinsonism may be predisposing factors for sporadic PD. Recent studies have demonstrated that mutations in PINK1 (PARK6 locus) gene, encoding PTEN-induced kinase 1, are associated with both familial recessive and sporadic early onset parkinsonism. In order to assess whether the coding variant A340T contributes to the risk of late-onset PD, we performed an association study of 539 PD patients with an onset age at or older than 50 and 525 controls in Chinese Han. Genotyping was performed by denaturing high performance liquid chromatography (DHPLC) combined with sequencing analyses. The A-allele frequency was 6.2% in PD and 4.2% in controls ( p = 0.0404), while G/A genotype frequencies were 12.4% in PD and 8.4% in the controls ( p = 0.0350). Our results yielded significant evidence for disease association between PINK1 A340T and PD with later onset (OR 1.55, 95% CI 1.04–2.32, p = 0.0393), thus suggesting that PINK1 A340T variant may contribute to the risk for late-onset PD in Chinese.

PINK1 mutations in sporadic early‐onset Parkinson's disease

Pathogenic PINK1 mutations have been described in PARK6-linked Parkinson's disease (PD) patients of Asian origin. However, data on the frequency of PINK1 mutations in sporadic early-onset Parkinson's disease (EOPD) Asian patients are lacking. The objectives of this study were to report the frequency of PINK1 mutations of sporadic EOPD in an Asian cohort comprising of ethnic Chinese, Malays, and Indians, and to highlight a PINK1-positive patient who presented with restless legs symptoms. Eighty consecutive sporadic EOPD patients from the movement disorder clinics of two major tertiary institutions in the country were included. We performed sequence analysis of all the coding and exon-intron junctions of the PINK1 using specific primer sets. In addition, we genotyped polymorphisms detected from the analysis in a group of sporadic PD patients and controls. Three different mutations (two homozygous nonsense and one heterozygous missense) in the putative kinase domain were found in three patients, giving a 3.7% frequency of PINK1 mutations in our EOPD cohort. All the mutations were absent in 200 healthy controls. One patient with a novel homozygous nonsense PINK1 mutation presented unusually with restless legs symptoms. Separately, analysis of the frequency of four PINK1 polymorphisms in a group of sporadic PD and controls did not reveal any significant differences. We highlight a 3.7% frequency of PINK1 mutations in an Asian cohort (ethnic Chinese, Malay, and Indian) of EOPD. The phenotypic spectrum associated with PINK1-positive patients may be wider than previously reported. Polymorphisms of PINK1 do not appear to modulate risk of PD in our population.

Genetic analysis of SCA2, 3 and 17 in idiopathic Parkinson's disease

Recent reports of SCA2 and SCA3 patients who presented with levodopa responsive parkinsonism have generated considerable interest as they have implications for genetic testing. It is unclear whether ethnic race alone or founder effects within certain geographical region explain such an association. In this study, we conducted genetic analysis of SCA2, 3, 17 in an ethnic Chinese cohort with early onset and familial Parkinson's disease (PD) and healthy controls. A total of 191 subjects comprising of 91 PD and 100 healthy controls were examined. We identified one positive case of SCA2 in an early-onset sporadic PD patient who had CAG 36 repeats, yielding a prevalence of 2.2% in early-onset sporadic PD patients and less than 1.0% in our study PD population. The size of the repeats was lower than the expanded repeats (38–57) in SCA2 patients with ataxia in our population. All the children of the patient were physically normal even though some of them carried the repeat expansion of similar size. No cases and controls were positive for SCA3 and SCA17. We do not think routine screening of SCA2, SCA3 and SCA17 for all idiopathic PD patients is cost-effective in our ethnic Chinese population. However, SCA2 should be a differential diagnosis in young onset sporadic PD when genetic mutations of other known PD genes have been excluded.

Analysis of the PINK1 gene in a cohort of patients with sporadic early-onset parkinsonism in Taiwan

Mutations in the PINK1 gene have been shown to cause autosomal recessive Parkinson's disease (PD) and/or early onset sporadic PD in Italy, Spain, North America, Ireland, and Asia. However, there are limited data on PINK1 mutations in sporadic early onset Asian PD patients. To determine the prevalence of PINK1 mutation in Taiwanese population, we conducted genetic analysis of PINK1 mutation in 73 early onset sporadic PD and 94 normal control subjects. We only identified a novel single heterozygous mutation R 407Q mutation in exon 6 of this gene in one patient at the age onset of 54. Overall, these data indicate that PINK1 mutations are rare in our population. Based on our results, unless common mutational hotspots are identified, routine testing for this mutation at least in our population may not be cost-effective.