Clinical and genetic studies on familial parkinsonism: the first report on a parkin gene mutation in a Taiwanese family

Genetic analysis of Parkin in early onset Parkinson's disease (PD): Novel intron 9 g > a single nucleotide polymorphism and risk of Taiwanese PD

Early onset Parkinson's disease (PD) has been associated with mutations in Parkin. We screened Parkin mutations in a cohort of Taiwanese early onset PD using direct cDNA sequencing. Two deletions (Ex2-3del and Ex5del), one point mutation (R334C), one 86-bp IVS9 insertion (c.1084intron(+)), and two polymorphisms (S167N and V380L) were identified. The mutations identified are heterozygous and none of the mutation carriers possess two Parkin mutations. The c.1084intron(+) was due to a novel IVS9 g > a change. To assess the association of IVS9 g > a, S167N and V380L with the risk of PD, we conducted a case-control study in a cohort of PD and ethnically matched controls. Although the difference is not significant, the V380L C allele frequency was notably lower in PD patients than the controls and a trend toward decrease in risk of developing PD was evident (odds ratio: 0.71, 95% confidence interval: 0.53-0.97, P = 0.029). Contrarily the IVS9 g > a a allele frequency was notably higher in PD patients than the controls and a trend toward increase in risk of developing PD was also evident (odds ratio: 1.65, 95% confidence interval: 1.06-2.59, P = 0.028). Quantitative real-time PCR showed that the relative Parkin c.1084intron(+) mRNA expression was increased in PD patients with IVS9 ga genotype as compared to gg genotype. Pairwise genotype analysis revealed that IVS9 gg genotype strengthens the negative association of the V380L GC genotype with PD (odds ratio: 0.67, 95% confidence interval: 0.48-0.94, P = 0.021). The results of Parkin mutation/polymorphism screening may contribute to our understanding of PD.

Genetic and DAT imaging studies of familial parkinsonism in a Taiwanese cohort

We here summarize the results of genetic investigations on a series of 82 parkinsonian patients from 60 families in Taiwan. We found 13 parkin patients in 7 families (12%), 2 PINK1 sibs from 1 family, and 1 LRRK2 patient from 1 family with I2012T mutation. We also identified SCA2 in 8 patients from 5 families (8%) and SCA3 in 3 patients from 1 family, all presenting with parkinsonian phenotype. In the available patients with parkin, PINK1, SCA2 and SCA3, the dopamine transporter (DAT) scan revealed that the reduction of uptake was primarily observed in the bilateral putamen, basically sharing a similar pattern with that in idiopathic Parkinson's disease. We concluded that the genetic causes contributed to about 25% of our series of familial parkinsonism. The parkin mutations and SCA2 were the most frequent genetic causes in our series with Chinese ethnicity. The results of DAT scan indicated that bilateral putamen was essentially involved in various genetically-caused familial parkinsonism.

DYT1 mutation in a cohort of Taiwanese primary dystonias

To investigate the DYT1 gene mutation in Chinese ethnic, we examined a series of 200 patients with primary dystonias (11 familial and 189 sporadic), 53 of their asymptomatic relatives, 97 patients with familial or early-onset parkinsonism, and 200 healthy subjects. The GAG deletion at codon 946 was only found in three sporadic dystonia patients and seven of their asymptomatic familial members. The frequency of GAG deletion was 1.5% in dystonia patients, and was 6.7% in early-onset dystonias (< or = 26 years). We conclude that DYT1 mutation is a minor cause of primary dystonias in a cohort of Taiwanese population.

Distribution, type, and origin of Parkin mutations: review and case studies

Early-onset Parkinson's disease (PD) has been associated with different mutations in the Parkin gene (PARK2). To study distribution and type of Parkin mutations, we carried out a comprehensive literature review that demonstrated two prominent types of mutations among 379 unrelated mutation carriers: exon rearrangements involving exon 3, 4, or both, and alterations in exons 2 and 7, suggesting mutational hot spots or founders. To elucidate the origin of 14 recurrent Parkin mutations in our samples, we carried out a detailed haplotype analysis at the PARK2 locus. Thirty-eight mutation-positive individuals, available family members, and 62 mutation-negative individuals were genotyped. We determined allele frequencies and linkage disequilibrium (LD) to evaluate the significance of shared haplotypes. We observed no LD between markers at PARK2. Our data support a common founder for the most frequent Parkin point mutation (924C>T; exon 7) and indicate a mutational hot spot as cause of a common small deletion (255/256delA; exon 2). Furthermore, the most frequent Parkin exon deletion (Ex4del) arose independently in 2 of our subjects. However, it also occurred as the result of a founder mutation in 2 cases that shared identical deletion break points. This study provides evidence for both mutational hot spots and founder mutations as a source of recurrent mutations in Parkin, regardless of the mutation type.

The parkinsonian phenotype of spinocerebellar ataxia type 3 in a Taiwanese family

We report a parkinsonian phenotype of spinocerebellar ataxia type 3 (SCA3) in three female sibs from one Taiwanese family, found in a genetic analysis of 60 patients from 49 families with familial parkinsonism. Initially, all three patients presented with early onset resting tremor, rigidity, bradykinesia, and good response to levodopa. In the later stages, peripheral neuropathy developed in one sib and mild ataxia in another one. Decreased concentration of dopamine transporter in the striatum was demonstrated by (99m)Tc-TRODAT-1 SPECT imaging in the two sibs studied. Therefore, SCA3 should be considered as an important etiology of familial parkinsonism.

Environmental risk factors of young onset Parkinson's disease: a case-control study

While the cause of Parkinson's disease (PD) remains unknown, recent evidence suggests certain environmental factors, such as well water drinking, herbicides and pesticides exposure, and neurotoxins, may trigger the chain of oxidative reactions culminating in the death of dopaminergic neurons in substantia nigra to cause parkinsonism. Most studies to date focused on PD with old age onset. However, there is a peculiar group of parkinsonian patients, the young onset Parkinson's disease (YOPD), in whom the age of onset is before 40. It is intriguing to know whether earlier exposure to the putative neurotoxin(s) may contribute to the earlier onset. We therefore conducted this case-control study in which 60 PD patients, 30 YOPD patients and the same number of age- and sex-matched young controls were included. Using logistic regression, we found well water drinking and head injury were risk factors for the development of YOPD. When YOPD patients were compared with PD, we found head injury and exercise were the significant predictors. Keeping all other variables constant, head injury was a risk factor and exercise appeared to be a protective factor. We conclude early exposure to well water drinking and head trauma may trigger and expedite the appearance of parkinsonian features, but such acceleration may be prevented through regular exercise.

Clinical, 18F-dopa PET, and genetic analysis of an ethnic Chinese kindred with early-onset parkinsonism and parkin gene mutations

We report on clinical (18)F-labeled 6-fluorodopa ((18)F-dopa) positron emission tomography (PET) and molecular genetic analyses of an ethnic Chinese family in which three siblings presented with early-onset Parkinson's disease. As described in some parkin patients, neither sleep benefit nor diurnal fluctuation was noted. Interestingly, depression, anxiety, and obsessive-compulsive disorders were manifest. The (18)F-dopa PET scans showed bilateral presynaptic dopaminergic dysfunction without marked lateralization. Molecular genetic analysis showed identical chromosome 6 haplotypes inherited by affected subjects, with alternate allelic deletions of parkin exons 3 and 4. Furthermore, mRNA analyses identified aberrantly spliced parkin transcripts, suggesting that unusual parkin protein isoforms may be expressed in the brain and retain some function.