Mutation analysis of the PINK1 gene in Southern Italian patients with early- and late-onset parkinsonism

Mutations in the PINK1 gene represent the second most frequent cause of early-onset Parkinson's disease (EOPD). One or two mutated alleles were also reported in some sporadic or familial patients suffering from late-onset Parkinson's disease (LOPD). We aimed at assessing the frequency of mutations in this gene in our population. We performed a sequence analysis of PINK1 in 115 patients diagnosed with Parkinson's disease (PD) from southern Italy, including 93 sporadic cases with EOPD, 9 familial cases with EOPD, and 13 familial cases with LOPD. Three known homozygous mutations (Q456X, W437X, Q126P), corresponding to a 2.6% of all cases, were found. In particular, one mutation was detected among the sporadic cases (1.0%), one mutation among the familial early-onset patients (11.1%) and one mutation among the familial late-onset patients (7.7%). In addition, we found two heterozygous mutations (E476K, R207Q) among the sporadic patients. Only one mutation (R207Q) had not been previously described. Our results assess the role played by PINK1 in EOPD in southern Italy and illustrate the existence of mutations in this gene also in the late-onset form of the disease.     

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. © 2009 Movement Disorder Society     

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 ≤ 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. © 2008 Movement Disorder Society     

Familial Parkinsonism and early onset Parkinson's disease in a Brazilian movement disorders clinic: Phenotypic characterization and frequency of SNCA,PRKN, PINK1, and LRRK2 mutations

The aim of the study was to evaluate the frequency and to perform phenotypic and genotypic characterization of familial Parkinsonism and early onset Parkinson's disease (EOPD) in a Brazilian movement disorder unit. We performed a standardized clinical assessment of patients followed by sequencing of PRKN, PINK1 in EOPD cases and SNCA, LRRK2 in familial Parkinsonism individuals. During the period of study (January through December, 2006), we examined 575 consecutive patients of whom 226 (39.3%) met the diagnosis of Parkinsonism and idiopathic Parkinson's disease (IPD) was diagnosed in 202 of the latter. Of the IPD cases, 45 (22.3%) had EOPD. The age at onset in the EOPD cases (n = 45) was 34.8 ± 5.4 years (mean ± standard deviation). The age at onset in the familial late‐onset PD patients (n = 8) was 52.3 ± 12.2 years. In the early onset cases, we identified five known mutations in PRKN, two single heterozygous and three compound heterozygous (P153R, T240M, 255Adel, W54R, V3I); in addition, we identified one novel mutation in PINK1 (homozygous deletion of exon 7). In the familial cases (late onset), 1 patient had a novel LRRK2 variant, Q923H, but no SNCA mutations were identified. We have demonstrated that EOPD accounts for a high frequency of IPD cases in our tertiary referral center. PRKN was the most commonly mutated gene, but we also identified a novel mutation in PINK1 and a novel variant in LRRK2. © 2009 Movement Disorder Society     

Heterozygous PINK1 mutations: A susceptibility factor for Parkinson disease?

PINK1 mutations cause recessively inherited early-onset Parkinson's disease (EOPD). We comprehensively tested 75 Serbian and 17 South Tyrolean EOPD patients for mutations in this gene and found three heterozygous mutation carriers. Two of these patients shared mutations with their affected relatives, further suggesting that heterozygous PINK1 mutations may act as a susceptibility factor for EOPD.     

Higher nigrostriatal dopamine neuron loss in early than late onset Parkinson's disease?—A [99mTc]‐TRODAT‐1 SPECT study

Early-onset Parkinson's disease (EOPD) is distinct from the classic late-onset PD (LOPD) because of its slower disease progression. The aim of this study was to compare dopamine neuronal loss in EOPD with that of LOPD with the same disease duration, through dopamine transporter (DAT) estimation. Fourteen patients, seven EOPD (<50 years) and seven LOPD, matched for disease duration were scanned with [(99m)Tc]-TRODAT-1-SPECT (INER-Taiwan), and were assessed with standard PD scales. EOPD patients had 34% lower striatal DAT binding potential (BP) compared with that of LOPD patients (BP = 0.29 +/- 0.12, BP = 0.44 +/- 0.12, P < 0.02) with similar PD severity. These results suggest that EOPD patients have greater dopamine density loss than LOPD patients without motor-symptom worsening.     

A new complex homozygous large rearrangement of the PINK1 gene in a Sudanese family with early onset Parkinson’s disease

PARK2 and PINK1 gene mutations are involved in recessive early onset Parkinson’s disease (EOPD). In order to determine the causative mutations in three affected sibs from a consanguineous Sudanese family with EOPD, multiplex ligation-dependent probe amplification was performed and revealed that the patients were homozygous for a deletion of PINK1 exons 4 to 8. Breakpoint analysis revealed a complex rearrangement combining a large deletion and the insertion of a sequence duplicated from the DDOST gene intron 2, located near the PINK1 gene. As breakpoint sequences displayed only three base pairs of homology, this rearrangement may result from Fork Stalling and Template Switching mechanism. This third large rearrangement of PINK1 enlarges the mutation spectrum and, together with recent published data in Tunisian patients with EOPD, points out that PINK1 gene analysis, including search for large rearrangement, should be considered in early onset recessive PD patients, particularly those from Arab origin.     

早发帕金森病临床特征、多巴转运体PET显像及基因突变分析

目的探讨早发帕金森病的临床特征、多巴胺功能改变和基因突变。方法选取作者医院收治的10例早发帕金森病患者(男、女各5例),发病年龄平均(31.4±8.0)岁,平均病程(3.0±0.8)年,无家族史,对所有患者的临床资料、多巴转运体PET显像及基因检测结果进行回顾性分析。结果 10例患者均有受累肢体运动迟缓及肌张力增高,6例出现静止性震颤,5例有足部肌张力障碍,4例腱反射活跃,2例腱反射亢进,4例存在日间症状波动。3例伴抑郁。9例患者对多巴丝肼反应良好。8例进行脑多巴胺转运体PET显像(11 C-CFT DATPET)检查,1例起病对侧壳核后部DAT降低,7例显示双侧壳核后部DAT降低,其中4例起病对侧DAT降低更为明显。1例parkin基因3、4外显子缺失,PINK1基因外显子1还发生重复突变。1例parkin基因外显子4出现了纯合突变。3例parkin基因外显子3或4发生杂合突变。结论早发帕金森病具有独特的临床特征,纹状体多巴胺功能发生改变,parkin基因和PINK1基因与其发病相关。     

Analysis of PARK genes in a Korean cohort of early-onset Parkinson disease

Mutations in five PARK genes (SNCA, PARKIN, DJ-1, PINK1, and LRRK2) are well-established genetic causes of Parkinson disease (PD). Recently, G2385R substitution in LRRK2 has been determined as a susceptibility allele in Asian PD. The objective of this study is to determine the frequency of mutations in these PARK genes in a Korean early-onset Parkinson disease (EOPD) cohort. The authors sequenced 35 exons in SNCA, PARKIN, DJ-1, PINK1, and LRRK2 in 72 unrelated EOPD (age-at-onset ≤50) recruited from ten movement disorders clinics in South Korea. Gene dosage change of the aforementioned genes was studied using multiple ligation-dependent probe amplification. We found four patients with PARKIN mutations, which were homozygous deletion of exon 4, compound heterozygous deletion of exon 2 and exon 4, heterozygous deletion of exon 4, and heterozygous nonsense mutation (Q40X). Four patients had PINK1 mutations; a compound heterozygous mutation (N367S and K520RfsX522) and three heterozygous mutations (G32R, R279H, and F385L). A missense mutation of SNCA (A53T) was found in a familial PD with autosomal dominant inheritance. Nine patients (12.5%) had heterozygous G2385R polymorphism of LRRK2, whereas none had G2019S mutation. However, no mutations were detected in DJ-1 and UCHL1 in our series. We identified genetic variants in PARKIN, PINK1, LRRK2, and SNCA as a cause or genetic risk factors for PD in 25% of Korean EOPD, and mutation of PARKIN was the most common genetic cause. Jung Mi Choi and Myoung Soo Woo equally contributed to this work.     

Genotype–phenotype correlates in Taiwanese patients with early‐onset recessive parkinsonism

We screened for mutations in the PARKIN, DJ‐1, and PINK1 genes in a Taiwanese cohort (68 probands; 58 sporadic and 10 familial) with early‐onset parkinsonism (EOP, onset <50 years of age). We identified 9 patients harboring mutations in PARKIN (three compound heterozygous and six single heterozygous carriers), 3 patients with heterozygous PINK1 mutations (including two novel substitutions M341I and P209A), and no DJ‐1 mutations. Our frequencies of PARKIN (two allele mutation, 4.4%; single allele, 8.8%) and PINK1 (single heterozygous, 4.4%) mutations in Taiwanese–Chinese are similar to those in Caucasian and other Asian EOP patients. Although the role of heterozygosity of recessive genes in EOP remains to be resolved, molecular analysis and functional imaging will play a decisive role in differential diagnosis and determined therapeutic strategy. © 2008 Movement Disorder Society     

Systematic Review and UK‐Based Study of PARK2 (parkin), PINK1, PARK7 (DJ‐1) and LRRK2 in early‐onset Parkinson's disease

Approximately 3.6% of patients with Parkinson's disease develop symptoms before age 45. Early‐onset Parkinson's disease (EOPD) patients have a higher familial recurrence risk than late‐onset patients, and 3 main recessive EOPD genes have been described. We aimed to establish the prevalence of mutations in these genes in a UK cohort and in previous studies. We screened 136 EOPD probands from a high‐ascertainment regional and community‐based prevalence study for pathogenic mutations in PARK2 (parkin), PINK1, PARK7 (DJ‐1), and exon 41 of LRRK2. We also carried out a systematic review, calculating the proportion of cases with pathogenic mutations in previously reported studies. We identified 5 patients with pathogenic PARK2, 1 patient with PINK1, and 1 with LRRK2 mutations. The rate of mutations overall was 5.1%. Mutations were more common in patients with age at onset (AAO) < 40 (9.5%), an affected first‐degree relative (6.9%), an affected sibling (28.6%), or parental consanguinity (50%). In our study EOPD mutation carriers were more likely to present with rigidity and dystonia, and 6 of 7 mutation carriers had lower limb symptoms at onset. Our systematic review included information from >5800 unique cases. Overall, the weighted mean proportion of cases with PARK2 (parkin), PINK1, and PARK7 (DJ‐1) mutations was 8.6%, 3.7%, and 0.4%, respectively. PINK1 mutations were more common in Asian subjects. The overall frequency of mutations in known EOPD genes was lower than previously estimated. Our study shows an increased likelihood of mutations in patients with lower AAO, family history, or parental consanguinity. © 2012 Movement Disorder Society.     

Variations of mitochondrial DNA polymerase γ in patients with Parkinson’s disease

Parkinson’s disease is associated with mitochondrial dysfunction. The POLG1 gene encodes DNA-polymerase γ, which is responsible for the replication of mitochondrial DNA. Mutations in POLG1 cause neurodegenerative diseases such as progressive external ophthalmoplegia and Alpers syndrome. In this study, we investigated if mutations in POLG1 had any correlation with Parkinson’s disease. Subjects consisted of Finnish patients with early-onset Parkinson’s disease (EOPD, N = 441) or late-onset Parkinson’s disease (LOPD, N = 263). The POLG1 gene was screened for nine previously known mutations. Two patients were compound heterozygotes with respect to putatively pathogenic alleles. Twenty-eight patients harbored a heterozygous missense mutation, but the allele frequencies did not differ from those of the controls. Interestingly, the frequency of affected siblings was 4.6-fold higher (95 % confidence interval; 1.09, 19.5) among the patients with EOPD and with heterozygous POLG1 mutations than among patients without mutations. Clinically the patients with or without POLG1 mutations did not differ from each other. Our findings provide two lines of evidence suggesting a role for POLG1 mutations in Parkinson’s disease: (1) identification of patients with compound heterozygous mutations in POLG1, and (2) higher frequency of affected siblings among the EOPD patients with heterozygous POLG1 mutations than among EOPD patients without mutations.     

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.     

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

BackgroundRecessive 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.MethodsThe 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.ResultsA 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.ConclusionsThe 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.     

Ultrasound-based motion analysis demonstrates bilateral arm hypokinesia during gait in heterozygous PINK1 mutation carriers

Carriers of a single heterozygous PINK1 (PTEN-induced putative kinase 1) gene mutation provide an ideal opportunity to study the development of parkinsonian motor signs from the very beginning. Measuring tools that reliably represent mild motor symptoms could also facilitate the assessment of future neuroprotective therapies and early diagnosis of Parkinson's disease (PD). We investigated nine family members carrying a heterozygous PINK1 mutation in comparison with 25 age-matched healthy controls. Arm kinematics were quantified during treadmill walking at four different speeds using ultrasound-based motion analysis. Heterozygous PINK1 mutation carriers showed a bilateral reduction of arm swing amplitudes (P = 0.003) and arm anteversion (P = 0.001), which was more pronounced on the predominantly affected body side but also was present, albeit to a lesser degree, contralaterally (amplitude P = 0.01, anteversion P = 0.002, repeated measures analysis of covariance [rmANCOVA]). Single post-hoc comparisons revealed similar results for all speeds on both body sides (P < 0.05) except for 2.0 km/h on the less affected side. A single heterozygous mutation in the PINK1 gene is associated with a bilateral dopaminergic dysfunction in this family. Ultrasound-based three-dimensional motion analysis of arm swing during gait is a suitable tool to quantify even subtle hypokinesia in mildly affected PINK1 mutation carriers, which tends to be easily overlooked on the less affected body side during clinical examination. Therefore, this technique is a promising application in early stage PD and in at-risk populations for the disease. © 2014 International Parkinson and Movement Disorder Society     

A voxel-based PET study of dopamine transporters in Parkinson's disease: relevance of age at onset

We used positron emission tomography (PET) and the dopamine transporter (DAT) ligand [(11)C]FECIT to measure loss of nigrostriatal dopaminergic neurons in early phase of early onset (EOPD) and late onset Parkinson's disease (LOPD). The analysis was carried out with both regions of interest and voxelwise method (SPM2), at group and single subject levels. Genetic analysis tested for the mutations occurring most frequently in Caucasian population. A significant, bilateral, asymmetric DAT reduction was observed in both EOPD and LOPD. Noteworthy, the side and severity of DAT binding reduction significantly correlated with the severity and asymmetry of motor clinical scores. The two EOPD patients carrying mutations in the PARK2 and PARK6 genes, respectively, displayed the lowest values, bilaterally. This work demonstrates that severity of nigrostriatal damage in early disease phase of sporadic PD is not dependent on age at onset. Genetically determined PD is associated with more severe and widespread dopaminergic impairment.     

Identification of the novel D297fsX318 PINK1 mutation and phenotype variation in a family with early-onset Parkinson's disease

Herein we first describe a novel homozygous single nucleotide deletion in PINK1 exon 4 (889delG) which results in a loss of kinase domain on the PINK1 protein (D297fsX318). This mutation was identified in two brothers with early-onset Parkinson disease (EOPD) from a Sicilian consanguineous family. Of note, while one of the two patients developed mental deterioration and psychiatric problems, the other showed no cognitive decline. The present study supports the view that PINK1 is a pathogenic gene in some Italian families with EOPD and contributes to define the PINK1-associated phenotype.     

Transcranial imaging of substantia nigra hyperechogenicity in a Taiwanese cohort of Parkinson's disease.

Transcranial Doppler imaging (TCDI) has been used as a noninvasive diagnostic tool to differentiate Parkinson's disease (PD) from atypical parkinsonism by detecting hyperechogenicity in the substantia nigra (SN). To our knowledge, no TCDI data are available for Asian populations, and TCDI sensitivity is uncertain across populations. Early-onset PD (EOPD) represents a specific PD subtype based on clinical features and pathogenic mechanisms. It is not known if EOPD patients have abnormal echogenicity in SN comparable to late-onset PD (LOPD) patients. We assessed the area of SN hyperechogenicity (hyper-SN) and a ratio of hyper-SN over ipsilateral midbrain (S/M ratio) with TCDI in 164 healthy Taiwanese, 40 EOPD patients, and 40 LOPD patients. The upper 95th percentile values for hyper-SN and S/M ratio were 0.20 cm(2) and 0.07. Our results indicate that S/M ratio is a more sensitive measure than hyper-SN in diagnosing PD. Approximately 92.5% of the LOPD patients and 57.5% of the EOPD patients had S/M ratios >/= 0.07. Enlarged hyperechogenicity of SN is a common finding in LOPD, but not in EOPD. Iron-independent mechanisms of SN cell degeneration in EOPD distinct from that in LOPD might contribute to the sonographic findings.     

Subclinical sensory abnormalities in unaffected PINK1 heterozygotes

Background   Mutations in the PINK1 gene, encoding a mitochondrial protein kinase, represent the second cause of autosomal recessive parkinsonism (ARP) after Parkin. While homozygous or compound heterozygous mutations in these genes are unequivocally causative of ARP, the role of single heterozygous mutations is still largely debated. An intriguing hypothesis suggests that these mutations could represent a risk factor to develop parkinsonism, by contributing to nigral cell degeneration. Since the substantia nigra plays an important role in temporal processing of sensory stimuli, as revealed from studies in idiopathic PD, we sought to investigate whether any subclinical sensory abnormalities could be detected in patients with PINK1- related parkinsonism and in unaffected PINK1 heterozygous carriers. Methods   We adopted a psychophysical method, the temporal discrimination paradigm, to assess PINK1 homozygous patients, unaffected relatives who were heterozygous carriers of the same mutations and healthy control subjects. Temporal discrimination threshold (TDT) and temporal order judgement (TOJ) for pairs of tactile, visual or visuo-tactile stimuli were measured according to a standardized protocol. Findings   Higher mean tactile and visuo-tactile TDTs and TOJs were detected in PINK1 mutation carriers, including not only homozygous patients but also healthy heterozygotes, compared to control subjects (for all comparisons, p < 0.001). Interpretation   In clinically unaffected subjects, the mere presence of a heterozygous PINK1 mutation is sufficient to determine sensory alterations which can be disclosed by a psychophysical task. Deficits in temporal processing might be considered as subclinical signs of alteration at least in PINK1-related parkinsonism.