Novel GIGYF2 gene variants in patients with Parkinson's disease in Chinese population

The Grb10-Interacting GYF Protein-2 gene (GIGYF2), located in the chromosomal region 2q36-q37, has been reported as a PARK11 gene with a causal role in familial Parkinson's disease (PD) in Italian and French populations. However, there is no comprehensive study of GIGYF2 gene conducted in Chinese patients with PD from mainland China. The 27 coding exons and intron/exon boundaries of the GIGYF2 gene were sequenced in 300 sporadic patients with Parkinson's disease. Eight heterozygous and one homozygous novel missense variants were identified in nine patients with PD, and not in 300 controls. p.Leu580Phe locates in the GYF domain and might interrupt the potentially function of GIGYF2 protein. Another variant Gln979stop encodes a truncated protein. In conclusion, we identified nine novel variants in GIGYF2 gene, which might be associated with PD in the Chinese population.     

GIGYF2 Asn56Ser mutation is rare in Chinese Parkinson's disease patients

Grb10-Interacting GYF Protein-2 gene (GIGYF2) has been suggested as a candidate gene for PARK11 locus since seven different GIGYF2 missense mutations were identified in familial Parkinson's disease (PD) patients of European descent. To evaluate the frequency and distribution of GIGYF2 Asn56Ser mutation in Chinese PD patients, we analyzed 469 patients with PD from mainland China, including 36 cases with familial PD and 433 cases with sporadic PD. A total of 451 subjects without neurological disorders from the same region in China were set as a control group. The result showed that the GIGYF2 Asn56Ser mutation was not present in all subjects. Our finding suggests that the GIGYF2 Asn56Ser mutation is rare in Chinese PD patients.     

Clinicogenetic study of GBA mutations in patients with familial Parkinson's disease

The glucocerebrosidase gene (GBA) is a known risk factor of Parkinson's disease (PD). We sequenced entire coding exons and exon/intron boundaries of GBA in 147 Japanese familial PD (FPD) patients from 144 families and 100 unrelated control subjects. Twenty-seven of 144 (18.8%) of index patients were heterozygous for known Gaucher disease mutations, suggesting that GBA heterozygous mutations are strongly associated with FPD (odds ratio = 22.9, 95% confidence interval = 3.1–171.2). The frequency was significantly higher in autosomal dominant PD (ADPD) compared with autosomal recessive PD. According to clinical assessments, PD patients with GBA mutations exhibited typical manifestations of PD or dementia with Lewy bodies (DLB), such as L-dopa responsive parkinsonism with psychiatric problems and/or cognitive decline. Interestingly, they also presented with reduced myocardial ¹²³I-metaiodobenzylguanidine uptake. Our findings suggest that heterozygous GBA mutations are strong risk factors in FPD, especially for autosomal dominant PD. Some patients with GBA heterozygous mutations develop clinical features of DLB. We speculate that GBA dysfunction may promote Lewy body formation, resulting in more severe PD or DLB phenotypes that are inherited in families.     

Lack of association between ATP13A2 Ala746Thr variant and Parkinson's disease in Han population of mainland China

ATP13A2 (PARK9) mutations are related to Kufor-Rakeb syndrome (KRS). We performed genetic analysis of the Ala746Thr variant in an independent cohort of the patients with PD and healthy controls from mainland China. The Ala746Thr variant was present in 1/532 (0.19%) of PD compared with 1/480 (0.21%) of healthy controls (odds ratio = 0.90, 95% CI 0.06, 14.39, P = 1.00). The two subjects carried the heterozygous genotype. Subset analysis in the group ≤50 years of age revealed a prevalence of 0.7% in PD compared with 0% in healthy controls and in the group >50 years of age showed 0% in PD versus 0.3% in healthy controls. We did not observe a significant association between Ala746Thr and Parkinson's disease in Han Chinese population, even after stratification by age at onset. The results suggested that Ala746Thr variant was not a major susceptible factor for PD in Han Chinese people.     

Mutation analysis of parkin and PINK1 genes in early-onset Parkinson's disease in China

A series of 69 Han Chinese PD patients (including 66 index cases and 3 relatives) with early-onset Parkinson's disease (EOPD) were studied to assess the frequency of parkin and PINK1 gene mutations. Mutation analysis of the parkin gene was performed by real-time quantitative polymerase chain reaction (QPCR), denaturing high-performance liquid chromatography (DHPLC) and DNA sequencing. For the PINK1 gene, DHPLC and DNA sequencing were used. Nineteen patients (including one relative) had mutation in the parkin gene, and the c.2T > C (p.M1T) was not reported previously. No mutation of the PINK1 gene was found. The onset age of the patients with mutations in the parkin was earlier than that of those without mutation (p < 0.05). We concluded that mutations in parkin gene are common in Chinese EOPD patients, and mainly are exon rearrangements, while mutation in PINK1 might be not common in Chinese EOPD patients.     

Mutational screening and zebrafish functional analysis of GIGYF2 as a Parkinson-disease gene

The Grb10-Interacting GYF Protein-2 (GIGYF2) gene has been proposed as the Parkinson-disease (PD) gene underlying the PARK11 locus. However, association of GIGYF2 with PD has been challenged and a functional validation of GIGYF2 mutations is lacking.In this frame, we performed a mutational screening of GIGYF2 in an Italian PD cohort. Exons containing known mutations were analyzed in 552 cases and 552 controls. Thereafter, a subset of 184 familial PD cases and controls were subjected to a full coding-exon screening. These analyses identified 8 missense variations in 9 individuals (4 cases, 5 controls).Furthermore, we developed a zebrafish model of gigyf2 deficiency. Abrogation of gigyf2 function in zebrafish embryos did not lead to a drastic cell loss in diencephalic dopaminergic (DA) neuron clusters, suggesting that gigyf2 is not required for DA neuron differentiation. Notably, gigyf2 functional abrogation did not increase diencephalic DA neurons susceptibility to the PD-inducing drug MPP+.These data, together with those recently reported by other groups, suggest that GIGYF2 is unlikely to be the PARK11 gene.     

Mutational analysis of FBXO7 gene in Parkinson's disease in a Taiwanese population

Mutations in the FBXO7 gene cause an autosomal-recessive early-onset parkinsonism with pyramidal tract signs. Its role in typical Parkinson's disease (PD) without pyramidal features is unclear. We assayed FBXO7 gene in 900 participants comprising 448 PD patients and 452 age- and sex-matched control subjects from Taiwan. The entire FBXO7 coding region and intron-exon boundaries were sequenced. We identified 2 novel missense substitutions, p.Ile87Thr and p.Asp328Arg, in a single heterozygous state in 2 early-onset PD patients individually (1.1% early-onset PD). These 2 variants were not observed in control subjects with a total of 904 normal alleles. Additionally, we also found 1 noncoding variant, exon 1 IVS-329C>T, modestly associated with PD. The frequency of the CT/TT genotype was higher in PD patients compared with control subjects (odds ratio, 1.43; 95% confidence interval, 1.02–2.01; p = 0.04). The clinical phenotypes of genetic variant carriers are similar to that seen in idiopathic PD. We conclude that FBXO7 gene contributes little to typical PD in our population. Further studies in other ethnic cohorts will be important to address its potential pathophysiological role in PD.     

Low frequency of common LRRK2 mutations in Mexican patients with Parkinson's disease

Mutations in leucine-rich repeat kinase 2 gene (LRRK2) account for as much as 5–6% of familial Parkinson's disease (PD) and 1–2% of sporadic PD. These mutations represent the most frequent cause of autosomal dominant PD, particularly in certain ethnic groups. In this first report concerning LRRK2 mutations in Mexican-mestizos, we screened 319 consecutive PD patients (186 males; 133 females; mean age at onset: 52.4 years) for LRRK2 mutations in exons 31 and 41 and for the mutation in exon 35, which produces the Y1699C substitution. Three (0.94%) patients, two with sporadic PD and one with familial PD (disease mean age at onset, 53.3 years), were heterozygous for LRRK2 mutations. Of these three, two patients had one of two different mutations in exon 31 (R1441G and R1441H, respectively); the other patient carried the G2019S mutation in exon 41. The Y1699C mutation was absent from this PD sample. Four additional subjects, unaffected relatives of one PD patient with a mutation in LRRK2, were subsequently genetically tested. None of the three LRRK2 mutations identified was present in 200 neurologically healthy Mexican control individuals. These findings have important implications for molecular testing of LRRK2 mutations in Mexican PD patients.     

Phactr2 and Parkinson's disease

Attempts at replicating the first genome-wide association study (GWAS) in Parkinson's disease (PD) have not successfully identified genetic risk factors. The present study reevaluates data from the first GWAS and focuses on the SNP (rs11155313, located in the Phactr2 gene) with the lowest P-value in the Tier 2 patient-control series. We employed four case-control series to examine the nominated SNP rs11155313 and identified association in US (OR: 1.39, P = 0.032), Canadian (OR: 1.41, P = 0.014) and Irish (OR: 1.44, P = 0.034) patient-control series, but not in the Norwegian series (OR: 1.15, P = 0.27). When combining all four series the observed trend was statistically significant (OR: 1.30, P < 0.001). This study shows that reappraisal of publicly available results of GWAS may help nominate new risk factors for PD.     

A novel LRRK2 mutation in a mainland Chinese patient with familial Parkinson's disease

Mutations in the leucine-rich repeat kinase 2 gene (LRRK2) are known to cause typical, late-onset familial Parkinson's disease in different geographic origins. However, there was no report about mutations of LRRK2 gene in mainland China. The 51 coding exons and intron/exon boundaries of the LRRK2 gene were sequenced in nine families with Parkinson's disease. A novel LRRK2 missense mutation resulting in a single amino acid substitution K616R was present in one family with a dominant form of PD, and not in 200 controls. The patient presented with slowly progressive resting tremor, dyskinesia, and responded well to l-dopa. In conclusion, we identified a novel mutation in LRRK2 gene, which was the first mutation of LRRK2 found in the mainland Chinese population with familial Parkinson's disease.     

Mutation analysis of LRRK2, SCNA, UCHL1, HtrA2 and GIGYF2 genes in Chinese patients with autosomal dorminant Parkinson's disease

Autosomal dorminant Parkinson's disease (ADPD) has been associated with mutations in the SCNA, LRRK2, UCHL1, HtrA2 and GIGYF2 genes. We studied the prevalence of variants in all five genes in 12 Chinese unrelated families with ADPD and 4 families with both essential tremor (ET) and Parkinson's disease (PD) phenotypes using direct sequencing analysis. We found 27 variants in the LRRK2 gene, eight in GIGYF2 gene, three in the SCNA and UCHL1 gene respectively, in which five variants were novel. However, no pathogenic mutations in the five genes were found in these families. Our result indicated that SCNA, LRRK2, UCHL1, HtrA2 and GIGYF2 genes' mutations might not be a main reason for Chinese ADPD.     

No evidence for pathogenic role of GIGYF2 mutation in Parkinson disease in Japanese patients

Grb10-Interacting GYF Protein-2 (GIGYF2) is a candidate gene for PARK11 locus. To date, seven different GIGYF2 missense mutations have been identified in patients with familial Parkinson disease (PD) of European descent. To clarify the pathogenic role of GIGYF2 in PD, we analyzed the frequency of GIGYF2 mutations in 389 Japanese patients with PD (including 93 patients with late-onset familial PD, 276 with sporadic PD, and 20 with a single heterozygous mutation in the PD-associated genes), and 336 Japanese normal controls, by direct sequencing and/or high-resolution melting analysis. None of the reported GIGYF2 mutations or digenic mutations were detected. Two novel non-synonymous variants were identified (p.Q1211delQ and p.H1023Q), however, we could not determine their roles in PD. In summary, we found no evidence for PD-associated roles of GIGYF2 mutations. Our data suggest that GIGYF2 is unlikely to play a major role in PD in Japanese patients, similar to other populations.     

ATP13A2 variability in Taiwanese Parkinson's disease

Mutations in ATP13A2 have been reported to associate with Parkinson's disease (PD). This study investigates the contribution of genetic variants in ATP13A2 to Taiwanese PD. ATP13A2 cDNA fragments from 65 early onset PD (onset <50 years) were sequenced. The identified variants were validated in a cohort of PD (n = 493) and ethnically matched controls (n = 585). A novel heterozygous G1014S, located at the conserved seventh transmembrane domain of ATP13A2 protein, was identified in an early onset PD patient, which was absent in 585 normal controls. Additionally, a reported heterozygous A746T was found in two PD patients and four controls. The clinical features and 99mTc‐TRODAT‐1 single photon emission computed tomography (SPECT) image of the patients carrying G1014S and A746T were similar to that of idiopathic PD. One normal control with A746T showed an asymmetric reduction of 99mT TRODAT‐1 uptake in the right striatum. Under oxidative stress or apoptotic stimulus, lymphoblastoid cells carrying either A764T or G1014S showed increased caspase 3 activity compared with the controls. The rates of decay for G1014S and A746T proteins were more or less reduced in cycloheximide chase experiment. In silico modeling of G1014S exhibited a more stable feature than wild‐type, and G1014S is mislocalized mainly in the intralysosomal space, which is coherent with the prediction of prohibiting N‐myristoylation and membrane association. We therefore hypothesize that rare variants of ATP13A2 may contribute to PD susceptibility in Taiwan. The role played by ATP13A2 variants in PD remains to be clarified. © 2011 Wiley‐Liss, Inc.     

MAPT IVS1+124 C>G modifies risk of LRRK2 G2385R for Parkinson's disease in Chinese individuals

Variants of the MAPT gene have been suggested to be associated with Parkinson's disease (PD) and to modify the risk for leucine-rich repeat kinase 2 (LRRK2) Parkinsonism. However, this has not been confirmed in Asians with ethnicity-specific variants of MAPT and LRRK2. In this study, Asian-specific LRRK2 p.G2385R variant and IVS1+124 C>G, a functional single-nucleotide polymorphism located in the MAPT promoter region, were genotyped in 561 Chinese PD patients and 556 control subjects. Allelic and genotypic frequencies of the 2 variants were compared between cases and control subjects independently and in combination. As a result, the LRRK2 p.G2385R variant alone was associated with an increased risk for PD (Odds ratio, 1.86; 95% confidence intervals, 1.08–3.19; p = 0.014), whereas MAPT IVS1+124 C>G was not (p = 0.34). However, the coexistence of MAPT IVS1+124C>G significantly enhanced the LRRK2 G2385R-conferred risk for PD (Odds ratio, 2.30; 95% confidence intervals, 1.14–4.54; p = 0.012). These results provide further evidence supporting the interaction between MAPT and LRRK2 genes, which increases the susceptibility to PD in Chinese individuals.     

Decreased expression of Bmal2 in patients with Parkinson's disease

Bmal1 is one of the central regulators of the clock machinery. Recently, we examined the expression profile of Bmal1 in total leukocytes for a 12h duration during the evening, overnight, and the morning, in subjects with Parkinson's disease (PD) and healthy controls. The results indicate that the expression of Bmal1 is significantly lower in PD patients versus control subjects. However, it is still unclear whether other key regulators of the clock machinery, especially Bmal2, the paralog of Bmal1, are also expressed differently in PD. To address this issue, the expression profiles of Bmal2, Clock, and Dec1 were examined in the same samples using real-time RT-PCR assay. The results show a difference in the expression pattern of Bmal2, but not Clock and Dec1. The expression of Bmal2 is significantly lower in PD at 21:00 h (p=0.005) and 00:00 h (p=0.025). These results together with our previous findings suggest that the molecular clock in total leukocytes is disturbed in PD patients.     

PINK1 polymorphism IVS1−7 A → G,exposure to environmental risk factors and anticipation of disease onset in Brazilian patients with early-onset Parkinson's Disease

Parkinson's disease (PD) etiology has been attributed both to genetic and environmental factors, although the exact mechanisms of its pathogenesis remains elusive. We investigated Brazilian early-onset PD (EOPD) patients with PINK1 polymorphisms (SNPs) in order to find possible correlations between SNPs, environmental exposure, and disease age of onset. We enrolled 48 patients and 61 controls. PINK1 SNPs and environmental exposure (living in rural areas, well-water drinking, exposure to pesticides, herbicides and organic solvents and smoking) were investigated in both groups. We divided our group of patients into four subgroups, according to the presence/absence of PINK1 SNP IVS1−7 A → G and the presence/absence of environmental factors exposure. We found a significant decrease (ANOVA test: p = 0.02) of age at disease onset in those patients that had the IVS1−7 A → G SNP and were exposed to environmental risk factors. Our data suggest that the interaction of PINK1 SNP IVS1−7 A → G and environmental risk factors together have an important role in EOPD: each of them individually has a minor influence, whereas their interaction is associated with a significant effect in anticipating the disease clinical onset.     

Investigation of TREM2, PLD3, and UNC5C variants in patients with Alzheimer's disease from mainland China

Recently, 3 rare coding variants significantly associated with Alzheimer's disease (AD) risk have been identified in western populations using whole exome sequencing method, including p.R47H in TREM2, p.V232M in PLD3, and p.T835M in UNC5C. To examine whether these variants are genetic risk factors in patients with AD from mainland China, we sequenced exon 2 of TREM2, exon 9 of PLD3, and exon 15 of UNC5C in Chinese Han population including 360 patients with AD and 400 control individuals. As a result, none of these 3 variants were identified in all subjects, however, 1 novel variant (p.A130V) in TREM2 and 4 novel variants (p.Q860H, p.T837K, p.S843G, and p.V836V) in UNC5C were detected in unrelated patients with late-onset AD. These findings suggest the 3 rare coding variants might not play an important role in AD risk in mainland China.     

Association between PARK16 and Parkinson's disease in the Han Chinese population: a meta-analysis

PARK16 was reported to alter the risk for Parkinson's disease (PD) in the Japanese population. However, its role in Han Chinese PD patients has not been well established. Herein, we investigated the effect of 4 single-nucleotide polymorphisms (SNPs) within the PARK16 locus, including rs823128, rs947211, rs823156, and rs11240572, on the risk of PD by genotyping 497 Taiwanese patients with PD and 500 age-matched control subjects. The results were then meta-analyzed with available genetic association studies in the same population. The meta-analysis showed that PD patients demonstrated a lower frequency of the rs823128 G allele (11.93%) than control subjects (14.04%; odds ratio [OR] 0.83, 95% confidence interval [CI] 0.72–0.96, p = 0.010). The frequency of the rs947211 A allele (40.35%) in PD patients was lower than in control subjects (43.01%; OR 0.90, 95% CI 0.80–0.99, p = 0.047). The rs823156 G allele was less frequently seen in PD patients (17.32%) than in control subjects (21.35%; OR 0.77, 95% CI 0.69–0.86, p < 0.001). A lower frequency of the rs11240572 A allele was found in PD patients (14.01%) than in control subjects (17.66%; OR 0.76, 95% CI 0.66–0.88, p < 0.001). Our results indicate a robust protective effect of PARK16 in Han Chinese PD patients. Functional approaches are needed to elucidate the effects of these SNPs on the regulation of gene expression.