SNCA polymorphisms, smoking, and sporadic Parkinson’s disease in Japanese

Resequencing the complete SNCA locus in Indian patients with Parkinson's disease

The genetic loci implicated in familial Parkinson's disease (PD) have limited generalizability to the Indian PD population. We tested mutations and the frequency of known mutations in the SNCA gene in a PD cohort from India. We selected 298 PD cases and 301 age-matched controls for targeted resequencing (before QC), along with 363 PD genomes of Indian ancestry and 1029 publicly available whole genomes from India as healthy controls (IndiGenomes), to determine the frequency of monogenic SNCA mutations. The raw sequence reads were analyzed using an in-house analysis pipeline, allowing the detection of small variants and structural variants using Manta. The in-depth analysis of the SNCA locus did not identify missense or structural variants, including previously identified SNCA mutations, in the Indian population. The familial forms of SNCA gene variants do not play a major role in the Indian PD population and this warrants further research in the under-represented population.

Failure of diet-induced transcriptional adaptations in alpha-synuclein transgenic mice

Nutritional influences have been discussed as potential modulators of Parkinson's disease (PD) pathology through various epidemiological and physiological studies. In animal models, a high-fat diet (HFD) with greater intake of lipid-derived calories leads to accelerated disease onset and progression. The underlying molecular mechanisms of HFD-induced aggravated pathology, however, remain largely unclear. In this study, we aimed to further illuminate the effects of a fat-enriched diet in PD by examining the brainstem and hippocampal transcriptome of alpha-synuclein transgenic mice exposed to a life-long HFD. Investigating individual transcript isoforms, differential gene expression and co-expression clusters, we observed that transcriptional differences between wild-type (WT) and transgenic animals intensified in both regions under HFD. Both brainstem and hippocampus displayed strikingly similar transcriptomic perturbation patterns. Interestingly, expression differences resulted mainly from responses in WT animals to HFD, while these genes remained largely unchanged or were even slightly oppositely regulated by diet in transgenic animals. Genes and co-expressed gene groups exhibiting this dysregulation were linked to metabolic and mitochondrial pathways. Our findings propose the failure of metabolic adaptions as the potential explanation for accelerated disease unfolding under exposure to HFD. From the identified clusters of co-expressed genes, several candidates lend themselves to further functional investigations.

Alpha-Synuclein Aggregation in Parkinson's Disease

Parkinson's disease (PD), a neurodegenerative disorder characterized by distinct aging-independent loss of dopaminergic neurons in substantia nigra pars compacta (SNpc) region urging toward neuronal loss. Over the decade, various key findings from clinical perspective to molecular pathogenesis have aided in understanding the genetics with assorted genes related with PD. Subsequently, several pathways have been incriminated in the pathogenesis of PD, involving mitochondrial dysfunction, protein aggregation, and misfolding. On the other hand, the sporadic form of PD cases is found with no genetic linkage, which still remain an unanswered question? The exertion in ascertaining vulnerability factors in PD considering the genetic factors are to be further dissevered in the forthcoming decades with advancement in research studies. One of the major proponents behind the prognosis of PD is the pathogenic transmutation of aberrant alpha-synuclein protein into amyloid fibrillar structures, which actuates neurodegeneration. Alpha-synuclein, transcribed by SNCA gene is a neuroprotein found predominantly in brain. It is implicated in the modulation of synaptic vesicle transport and eventual release of neurotransmitters. Due to genetic mutations and other elusive factors, the alpha-synuclein misfolds into its amyloid form. Therefore, this review aims in briefing the molecular understanding of the alpha-synuclein associated with PD.

Genetic Analysis and Literature Review of SNCA Variants in Parkinson's Disease

Parkinson's disease (PD) is the fastest-growing neurodegenerative disorder. Aging, environmental factors, and genetics are considered as risk factors. The alpha-synuclein gene (SNCA), the first pathogenic gene identified in a familial form of PD, was indisputably involved as a heritable component for familial and sporadic PD. In this study, whole-exome sequencing and Sanger sequencing were performed to evaluate the association between the SNCA gene variants and PD. The genetic data of 438 clinically diagnosed patients with PD and 543 matched control populations of the Han Chinese were analyzed. The literature review of SNCA variants for 231 cases reported in 89 articles was extracted from the PubMed and the Movement Disorder Society Genetic mutation database. No potentially causative variant(s) in the SNCA gene, excepting two single-nucleotide nonsynonymous variants c.158C>T (p.A53V, rs542171324) and c.349C>T (p.P117S, rs145138372), were detected. There was no statistically significant difference in the genotypic or allelic frequencies for either variant between the PD group and the control group (all P > 0.05). No copy number variants of the SNCA gene were detected. The results of this study suggest that the variants in the exons of the SNCA gene may have less or no role in the development of PD in the Han Chinese populations. The literature review suggests that psychiatric signs and cognitive decline/dementia were more common among patients with SNCA duplication or triplication (psychiatric signs: χ² = 7.892, P = 0.005; cognitive decline/dementia: χ² = 8.991, P = 0.003).

α-syn and SNP rs356219 as a potential biomarker in blood for Parkinson's disease in Mexican Mestizos

Clinical criteria diagnose Parkinson's disease (PD), therefore, it is crucial to find biological elements that could support diagnosis or even act as prognostic tools of PD. The SNCA gene codifies a protein called α - synuclein; several studies associate genetic and biochemical factors of SNCA with PD, including transcript and plasmatic protein levels, however, contradictory evidence indicates inconclusive results. We aim to compare SNCA mRNA expression, plasmatic α-syn protein and rs356219 SNP between PD cases and a control group, and to identify a potential biomarker in Mexican mestizos', focusing on these three components determined in blood. We included 88 PD patients and 88 age-matched controls. We observed higher α-syn protein and decreased SNCA mRNA levels in PD subjects, compared to control group (p = 0.044 and p < 0.001, respectively). A statistically significant difference was found in allelic and genotypic frequencies of SNP rs356219 between PD patients and normal subjects (p = 0.006 and p = 0.023, respectively). Logistic regression analysis determined as optimal predictors of PD the GG genotype of SNP rs356219 (OR 2.49; p = 0.006) in a recessive model and α-syn protein (OR 1.057; p = 0.033). Furthermore, the G allele of SNP rs356219 was associated with higher plasmatic α-syn and mRNA levels in PD subjects. The receiver operating curves (ROC) distinguished PD from healthy controls with good sensitivity and specificity considering the plasmatic α-syn protein (AUC = 0.693, Sensitivity = 66.7 %, Specificity = 63.9 %) or a predictive probability of plasmatic α-syn protein and SNP rs356219 in a single model (AUC = 0.692, Sensitivity = 62.3 %, Specificity = 62.5 %). The performance of this classifier model in PD at early stage (n = 31) increase the discriminant power in both, plasmatic α-syn protein (AUC = 0.779, Sensitivity = 72.7 %, Specificity = 73.9 %) and predictive probability (AUC = 0.707, Sensitivity = 63.6 %, Specificity = 62.5 %). We propose that α-syn protein and SNP rs356219 together may work as a good signature of PD, and they can be suggested as a non-invasive biomarker of PD risk.

Alpha synuclein (SNCA) rs7684318 variant contributes to Parkinson's disease risk by altering transcription factor binding related with Notch and Wnt signaling

In view of inconsistencies in the association studies of alpha synuclein (SNCA) rs7684318 (chr4: 90655003 T > C) with Parkinson's disease (PD), we conducted a meta-analysis to establish the association of this variant with PD and examined changes in transcription factor binding. SNCA rs7684318 C-allele was identified as genetic risk factor for PD in fixed (OR: 1.53, 95 % CI: 1.40-1.68, p < 0.0001) and random effect (OR: 1.65, 95 % CI: 1.30-2.09, p = 0.0003) models. Heterogeneity was observed in association (Tau²: 0.0576, H: 2.32, I²: 0.815, Q: 21.64, p = 0.0002). Egger's test showed no evidence of publication bias (p = 0.37). Subgroup analysis showed that rs7684318 is contributing to PD risk in Japanese (OR: 1.46, 95 % CI: 1.30-1.64) and Indian (OR: 2.63, 95 % CI: 1.79-3.86) populations while showing no significant association in Chinese population (OR: 1.68, 95 % CI: 0.93-3.02). Sensitivity analysis showed that exclusion of any one of the studies has no significant impact on the association, which justifies the robustness of the analysis. Tissue-specific DNase foot print analysis revealed that this variant contributes to increased transcription factor binding in midbrain, putamen and caudate nucleus. The substitution of T > C increased binding of RBPJ and GATA-family transcription factors; and decreased binding of NKX2 family, SNAI2, SNAI3, DMRT1, HOXA13, HOXB13, HOXC13, HOXD13, WT1, POU4F1, POU4F2, POU4F3 transcriptional factors. TRANSFAC and DNA curvature analyses substantiate the association of this variant with increased binding of GATA1 that contribute to intensity of DNA curvature peaks and splitting pattern. These studies along with the meta-analysis strongly suggest that the rs7684318 variant contributes to the pathophysiology of PD by modulating binding of transcription factors related to Notch and Wnt signalling pathways that are likely to impair dopmanergic transmission.

Interaction between SNCA gene polymorphisms and T2DM with Parkinson's disease

AIMS

To investigate the association of several single nucleotide polymorphisms (SNPs) within alpha-synuclein (SNCA) gene and additional gene-environment interaction with Parkinson's disease (PD) risk.

METHODS

Hardy-Weinberg equilibrium (HWE) is tested for controls using SNPstats (http://bioinfo.iconcologia.net/SNPstats). Logistic regression is used to calculate the ORs (95% CI) for relations between the four SNPs and PD risk. The generalized multifactor dimensionality reduction (GMDR) model is used to evaluate the synergy between gene and environment.

RESULTS

A total of 1161 people were included in this study, including 386 cases of PD and 775 normal controls. In this study, the genotype frequency of the control group was consistent with HWE distribution. Rs356219-G allele frequency was 30.0% in patients and 19.8% in control group. The rs356221-T allele frequency was 29.7% in the patients and 20.8% in the control group. Rs356219-G and rs356221-T alleles were associated with increased PD risk, with adjusted ORs (95% CI) of 1.92 (1.28-2.52) and 1.52 (1.05-2.02), respectively. We also found no significant correlation between rs2301134 and rs2301135 and susceptibility to PD. The best gene-environment interaction models were determined by GMDR analysis, which shown a significant gene-T2DM interaction combinations, but the gene-alcohol drinking interaction combinations were all not significant. We also conducted stratified analysis for interaction effect using logistic regression. We found that T2DM patients with rs356221-AT/ TT genotype have the highest PD risk, compared to subjects with rs356219-AA genotype, OR (95%CI) = 2.67 (1.83-3.46).

CONCLUSIONS

The rs356219-G and rs356221-T, gene-environment interaction between rs356221 and T2DM were all associated with increased PD risk.

Association between SNCA rs356220 polymorphism and Parkinson's disease: A meta-analysis

Several studies have investigated the correlation between single nucleotide polymorphism (SNP) rs356220 in the α-synuclein (SNCA) gene and Parkinson's disease (PD) with inconsistent results. Herein, a meta-analysis was conducted to ascertain the association of the SNCA rs356220 polymorphism with the risk of PD. Six eligible articles involving 5333 PD cases and 5477 controls were included in this meta-analysis. The pooled odds ratios (OR) and 95 % confidence interval (CI) were calculated to estimate the association. The fixed or random effect was selected based on the homogeneity among studies. Heterogeneity was detected by I². We performed sensitivity analysis to test the stablility of the results. Publication bias was evaluated by Funnel plot and Begg's test. The pooled results showed a significant association between SNCA rs356220 gene polymorphism and PD susceptibility in the codominant (FEM: OR = 1.31, 95 % CI = 1.24-1.39), dominant (FEM: OR = 1.38, 95 % CI = 1.27-1.49) and recessive (FEM: OR = 1.52, 95 % CI = 1.38-1.68) models. Furthermore, in the subgroup analysis stratified by ethnicity, increased risk of PD was identified in both Caucasian and Asian populations. Overall, the present meta-analysis provided evidence supporting that SNCA rs356220 polymorphism might act as a genetic susceptibility factor for PD.

A Comprehensive Analysis of the Association Between SNCA Polymorphisms and the Risk of Parkinson's Disease

Background: Various studies have reported associations between synuclein alpha (SNCA) polymorphisms and Parkinson's disease (PD) risk. However, the results are inconsistent. We conducted a comprehensive meta-analysis of the associations between SNCA single-nucleotide polymorphisms (SNPs) and PD risk in overall populations and subpopulations by ethnicity.

Methods: Standard meta-analysis was conducted according to our protocol with a cutoff point of p < 0.05. To find the most relevant SNCA SNPs, we used a cutoff point of p < 1 × 10⁻⁵ in an analysis based on the allele model. In the subgroup analysis by ethnicity, we divided the overall populations into five ethnic groups. We conducted further analysis on the most relevant SNPs using dominant and recessive models to identify the contributions of heterozygotes and homozygotes regarding each SNP.

Results: In our comprehensive meta-analysis, 24,075 cases and 22,877 controls from 36 articles were included. We included 16 variants in the meta-analysis and found 12 statistically significant variants with p < 0.05. After narrowing down the variants using the p < 1 × 10⁻⁵ cutoff, in overall populations, seven SNPs increased the risk of PD (rs2736990, rs356220, rs356165, rs181489, rs356219, rs11931074, and rs2737029, with odds ratios [ORs] of 1.22–1.38) and one SNP decreased the risk (rs356186, with an OR of 0.77). In the East Asian group, rs2736990 and rs11931074 increased the risk (with ORs of 1.22–1.34). In the European group, five SNPs increased the risk (rs356219, rs181489, rs2737029, rs356165, and rs11931074, with ORs of 1.26–1.37) while one SNP decreased the risk (rs356186, with an OR of 0.77). The heterozygotes and homozygotes contributed differently depending on the variant.

Conclusions: In summary, we found eight SNCA SNPs associated with PD risk, which had obvious differences between ethnicities. Seven SNPs increased the risk of PD and one SNP decreased the risk in the overall populations. In the East Asian group, rs2736990 and rs11931074 increased the risk. In the European group, rs356219, rs181489, rs2737029, rs356165, and rs11931074 increased the risk while rs356186 decreased the risk. Variants with the highest ORs and allele frequencies in our analysis should be given priority when carrying out genetic screening.

Association between SNCA rs2736990 polymorphism and Parkinson's disease: a meta-analysis

Emerging evidence suggests that the SNP rs2736990 of SNCA is a susceptibility factor for idiopathic Parkinson's disease (PD) in different populations, but the studies which examined the association have provided inconsistent results. Therefore, we performed a meta-analysis of some case-control studies to obtain a more exact estimation of there associations. All the relevant studies were extracted from PubMed, Embase, EBSCO, Chineses national knowledge infrastructure, Google Scholar and Wanfang databases (up to February 2017). A total of six studies with 2525 PD cases and 2165 controls were eventually enrolled in the present meta-analysis based on the strict inclusion and exclusion criteria. The pooled analysis showed that there is a significant association between rs2736990 polymorphism and PD susceptibility in all genetic models (T vs. C: OR=0.772, 95%CI: 0.709-0.840, P=0.001; TT vs. CC: OR=0.586, 95%CI: 0.490-0.701, P=0.001; TC vs. CC: OR=0.814, 95%CI: 0.716-0.925, P=0.002; TT+TC vs. CC: OR=0.752, 95%CI: 0.666-0.848, P=0.001; TT vs. TC+CC: OR=0.658, 95%CI: 0.561-0.772, P=0.001). Our meta-analysis provides evidence that the T allele, TT and TC genotype of rs2736990(C/T) polymorphism may decrease the risk of PD.

Genetic Variants in SNCA and the Risk of Sporadic Parkinson's Disease and Clinical Outcomes: A Review

There is increasing evidence of the contribution of genetic susceptibility to the etiology of Parkinson's disease (PD). Genetic variations in the SNCA gene are well established by linkage and genome-wide association studies. Positive associations of single nucleotide polymorphisms (SNPs) in SNCA and increased risk for PD were found. However, the role of SNCA variants in individual traits or phenotypes of PD is unknown. Here, we reviewed the current literature and identified 57 studies, performed in fourteen different countries, that investigated SNCA variants and susceptibility to PD. We discussed the findings based on environmental factors, history of PD, clinical outcomes, and ethnicity. In conclusion, SNPs within the SNCA gene can modify the susceptibility to PD, leading to increased or decreased risk. The risk associations of some SNPs varied among samples. Of notice, no studies in South American or African populations were found. There is little information about the effects of these variants on particular clinical aspects of PD, such as motor and nonmotor symptoms. Similarly, evidence of possible interactions between SNCA SNPs and environmental factors or disease progression is scarce. There is a need to expand the clinical applicability of these data as well as to investigate the role of SNCA SNPs in populations with different ethnic backgrounds.

Nicotine from cigarette smoking and diet and Parkinson disease: a review

Evidence from epidemiological studies suggest a relationship between cigarette smoking and low risk of Parkinson disease (PD). As a major component of tobacco smoke, nicotine has been proposed to be a substance for preventing against PD risk, with a key role in regulating striatal activity and behaviors mediated through the dopaminergic system. Animal studies also showed that nicotine could modulate dopamine transmission and reduce levodopa-induced dyskinesias. However, previous clinical trials yield controversial results regarding nicotine treatment. In this review, we updated epidemiological, preclinical and clinical data, and studies on nicotine from diet. We also reviewed interactions between genetic factors and cigarette smoking. As a small amount of nicotine can saturate a substantial portion of nicotine receptors in the brain, nicotine from other sources, such as diet, could be a promising therapeutic substance for protection against PD.

Variants in SNCA Gene Are Associated with Parkinson's Disease Risk and Cognitive Symptoms in a Brazilian Sample

Genetic susceptibility contributes to the etiology of sporadic Parkinson's Disease (PD) and worldwide studies have found positive associations of polymorphisms in the alpha-synuclein gene (SNCA) with the risk for PD. However, little is known about the influence of variants of SNCA in individual traits or phenotypical aspects of PD. Further, there is a lack of studies with Latin-American samples. We evaluated the association between SNCA single nucleotide polymorphisms (single nucleotide polymorphisms, SNPs - rs2583988, rs356219, rs2736990, and rs11931074) and PD risk in a Brazilians sample. In addition, we investigated their potential interactions with environmental factors and specific clinical outcomes (motor and cognitive impairments, depression, and anxiety). A total of 105 PD patients and 101 controls participated in the study. Single locus analysis showed that the risk allele of all SNPs were more frequent in PD patients (p < 0.05), and the associations of SNPs rs2583988, rs356219, and rs2736990 with increased PD risk were confirmed. Further, the G-rs356219 and C-rs2736990 alleles were associated with early onset PD. T-rs2583988, G-rs356219 and C-2736990 alleles were significantly more frequent in PD patients with cognitive impairments than controls in this condition. In addition, in a logistic regression model, we found an association of cognitive impairment with PD, and the practice of cognitive activity and smoking habits had a protective effect. This study shows for the first time an association of SNCA polymorphism and PD in a South-American sample. In addition, we found an interaction between SNP rs356219 and a specific clinical outcome, i.e., the increased risk for cognitive impairment in PD patients.

SNCA rs356182 variant increases risk of sporadic Parkinson's disease in ethnic Chinese

PURPOSE

A genome-wide association study (GWAS) has recently identified a novel single nucleotide polymorphism (SNP) rs356182 at SNCA that can modulate the risk of Parkinson's disease (PD) in Caucasian ancestry. The present study was designed to clarify the strength of the association in ethnic Chinese population.

METHODS

Using a case-control methodology, we genotyped the SNP rs356182 to investigate the association with risk of PD. A total of 2205 ethnic Han Chinese study subjects comprising 1053 sporadic PD patients (581 males, 472 females) and 1152 controls (604 males, 548 females) were recruited from Mainland China. Additionally, the SHEsis software platform was applied for linkage disequilibrium (LD) analysis between rs356182 and another PD-associated synuclein SNP rs356219 we previously reported.

RESULTS

The frequency of SNCA rs356182-G allele was significantly higher in PD group than that in controls (odds ratio (OR)=1.470, 95% confidence interval (CI): 1.284-1.683, P=2.306E-8). Subjects carrying GG/AG genotype had an increased risk compared with the AA carriers (OR=1.162, 95% CI: 1.143-2.274, P=0.006). Among all the genotypes of rs356182, GG genotype showed the strongest association with risk of PD (GG vs. AG/AA, OR=1.620, 95% CI: 1.368-1.919, P=2.001E-8). However, the gender, onset age, disease duration, Hoehn-Yahr stage, UPDRS scores and other clinical features were similar between GG genotype carriers and non-carriers. No LD between rs356182 and rs356219 was found in our population (r(2)=0.016 and D'=0.163).

CONCLUSION

Our study firstly demonstrates that SNCA rs356182 variant has an increased risk of susceptibility to PD in Han Chinese population. Further functional analysis is required to determine the role of this SNP in development of PD.

SNCA Gene Polymorphism may Contribute to an Increased Risk of Alzheimer's Disease

BACKGROUND

The purpose of this study is to elucidate the association between α-synuclein (SNCA) polymorphisms and the risk of Alzheimer's disease (AD).

METHODS

The PCR-RFLP was applied to detect SNCA gene rs6532190, rs3775430, and rs10516846 polymorphisms in 98 AD patients and 105 healthy elderly.

RESULTS

The GG frequency of rs10516846 was evidently increased in AD group than control group (P < 0.05). There was a significant difference in SNCA level between the AD and control groups (P < 0.01). In the AD group, the SNCA level in cerebrospinal fluid of GG (rs10516846) carriers was increased as compared with AA carriers (P < 0.05). The GG (rs10516846) frequency of the early-onset AD group is significantly higher than that of the late-onset AD group (P < 0.05). The frequency of rs3775430 GG was lower in the early-onset group than that in the late-onset group (0% vs. 16.7%). The SNCA level in cerebrospinal fluid of GG (rs10516846) carriers in the early-onset AD group is higher than that of AA carriers (P < 0.05).

CONCLUSION

SNCA gene polymorphism may be associated with an increased risk of AD and GG genotype of rs10516846 and elevated SNCA level in CSF may increase the risk of early-onset AD.

Genetic Profile, Environmental Exposure, and Their Interaction in Parkinson's Disease

The discovery of causative mutations for Parkinson's disease (PD) as well as their functional characterization in cellular and animal models has provided crucial insight into the pathogenesis of this disorder. Today, we know that PD pathogenesis involves multiple related processes including mitochondrial dysfunction, oxidative and nitrative stress, microglial activation and inflammation, and aggregation of α-synuclein and impaired autophagy. However, with the exception of a few families with Mendelian inheritance, the cause of PD in most individuals is yet unknown and the identified genetic susceptibility factors have only small effect size. Epidemiologic studies have found increased risk of PD associated with exposure to environmental toxicants such as pesticides, organic solvents, metals, and air pollutants, while reduced risk of PD associated with smoking cigarettes and coffee consumption. The role of environmental exposure, as well as the contribution of single genetic risk factors, is still controversial. In most of PD cases, disease onset is probably triggered by a complex interplay of many genetic and nongenetic factors, each of which conveys a minor increase in the risk of disease. This review summarizes the current knowledge on causal mutation for PD, susceptibility factors increasing disease risk, and the genetic factors that modify the impact of environmental exposure.

SNCA variants rs2736990 and rs356220 as risk factors for Parkinson's disease but not for amyotrophic lateral sclerosis and multiple system atrophy in a Chinese population

Previous studies found that polymorphisms rs2736990 and rs356220 in the alpha-synuclein (SNCA) gene increase the risk for Parkinson's disease (PD) in a Caucasian population. In consideration of the overlapping of clinical manifestations and pathologic characteristics among PD, amyotrophic lateral sclerosis (ALS), and multiple system atrophy (MSA), the possible associations of these 2 polymorphisms and 3 neurodegenerative diseases were studied in the Chinese population. A total of 1011 PD, 778 sporadic ALS (SALS), 264 MSA patients, and 721 healthy controls (HCs) were studied. All subjects were genotyped for the 2 polymorphisms using polymerase chain reaction and direct sequencing. Significant differences in the genotype frequencies (p = 0.0188 and 0.0064, respectively) and minor allele frequencies (MAFs) (p = 0.0065 and 0.0095, respectively) of rs2736990 and rs356220 were observed between the PD patients and HCs. Moreover, significant differences were found between the early-onset PD patients (<50 years) and matched controls but not in the late-onset PD patients (≥50 years). However, no differences were observed between subgroups with regard to clinical features, such as sex, onset symptoms (tremor or rigidity), cognition (normal or abnormal), and anxiety and depression (presence or absence). No significant differences were found in the genotype frequencies and MAFs of these 2 single-nucleotide polymorphisms between SALS patients and HCs and between MSA patients and HCs. No significant differences were found between subgroups with regard to the clinical presentation of SALS and MSA. Our results show that rs2736990 and rs356220 in SNCA decreased the risk for PD in a Chinese population. These candidate polymorphisms were unlikely to be the causes of SALS and MSA in this population.

Neuropathology of cigarette smoking

It is well established that cigarette smoking is hazardous to health and is a risk factor for many chronic diseases. However, its impact on the brain, whether it be from prenatal exposure to maternal cigarette smoking, cerebrovascular disease, Alzheimer's disease (AD) or Parkinson's disease, is still not very clear. Neuroimaging and neuropathological investigations suggest that there are heterogeneous effects of cigarette smoking on the brain. On the one hand, it is quite clear that cigarette smoking causes damage to endothelial cells, resulting in increased risk of cerebrovascular disease. On the other hand, it seems to be associated with different Alzheimer's pathologies in post-mortem brains and experimental models, despite the fact that epidemiological studies clearly indicate a positive correlation between cigarette smoking and increased risk for AD. Interestingly, cigarette smoking appears to be associated with reduced Parkinson's pathology in post-mortem brains. However, although nicotine in cigarettes may have some neuroprotective actions, the effects of all the other toxic compounds in cigarettes cannot be ignored. It is, therefore, our aim to summarize what is known about the neuropathology of cigarette smoking and, in particular, its implications for neurodegenerative diseases.

Analysis of genome-wide association study-linked loci in Parkinson's disease of Mainland China

BACKGROUND

Genome-wide association studies (GWAS) have identified numerous single-nucleotide polymorphisms (SNPs) that can modulate the risk of developing Parkinson's disease (PD).

METHODS

We investigated the association of previously identified loci in a Mainland Chinese population to identify a possible ethnic-specific effect with GWAS analysis. Seventeen SNPs were genotyped from those loci using case-control methodology to analyze a total of 1,737 individuals.

RESULTS

Strong evidence of an association for reference SNP 894278 (rs894278) and rs11931074 on 4q22 throughout the α synuclein (SNCA) region was observed in our study. The SNP rs894278 confers risk via a dominant model and an additive model, whereas the minor allele G of rs11931074 reduces the risk of PD progression. The minor allele frequency of rs11724635 produced weaker signals for PD, but this was not replicated in the genotype after adjusting for age and sex.

CONCLUSIONS

This study yields new clues about GWAS-linked data in patients with PD from Mainland China.

SNCA rs356219 variant increases risk of sporadic Parkinson's disease in ethnic Chinese

Alpha-synuclein gene (SNCA) polymorphisms have been associated with Parkinson's disease (PD). A recently published genome-wide association study (GWAS) meta-analysis from the USA and Europe found a strong association between SNCA rs356219 and PD. Considering the population-specific heterogeneity, we investigated the role of SNCA rs356219 as PD susceptibility in a large Han Chinese population of 685 patients and 569 controls. The SNCA rs356219-G allele was found to increase the risk to develop PD (OR = 1.81, 95% CI: 1.54-2.13, P = 5.71E-13). The meta-analysis revealed that the frequency of AG + GG genotypes higher in PD than in control subjects (OR = 1.85, 95% CI: 1.56-2.19, P = 0.00001) in the Asian population. PD patients with AG + GG genotypes were associated with earlier age at onset compared with those with AA genotype. No such significant association was observed in the clinical presentation for gender, age at onset, and onset symptoms. Our study provides strong support for the susceptibility role of SNCA rs356219 in sporadic PD in a Han Chinese population from mainland China and the meta-analysis also revealed a similar finding in the Asian population.

UCHL1 S18Y variant is a risk factor for Parkinson's disease in Japan

Background

A recent meta-analysis on the UCHL1 S18Y variant and Parkinson’s disease (PD) showed a significant inverse association between the Y allele and PD; the individual studies included in that meta-analysis, however, have produced conflicting results. We examined the relationship between UCHL1 S18Y single nucleotide polymorphism (SNP) and sporadic PD in Japan.

Methods

Included were 229 cases within 6 years of onset of PD, defined according to the UK PD Society Brain Bank clinical diagnostic criteria. Controls were 357 inpatients and outpatients without neurodegenerative disease. Adjustment was made for sex, age, region of residence, smoking, and caffeine intake.

Results

Compared with subjects with the CC or CA genotype of UCHL1 S18Y SNP, those with the AA genotype had a significantly increased risk of sporadic PD: the adjusted OR was 1.57 (95 % CI: 1.06 − 2.31). Compared with subjects with the CC or CA genotype of UCHL1 S18Y and the CC or CT genotype of SNCA SNP rs356220, those with the AA genotype of UCHL1 S18Y and the TT genotype of SNP rs356220 had a significantly increased risk of sporadic PD; the interaction, however, was not significant. Our previous investigation found significant inverse relationships between smoking and caffeine intake and PD in this population. There were no significant interactions between UCHL1 S18Y and smoking or caffeine intake affecting sporadic PD.

Conclusions

This study reveals that the UCHL1 S18Y variant is a risk factor for sporadic PD. We could not find evidence for interactions affecting sporadic PD between UCHL1 S18Y and SNCA SNP rs356220, smoking, or caffeine intake.