Association study of rs6812193 polymorphism with Parkinson's disease in a Greek population

The endo-lysosomal system in Parkinson's disease: expanding the horizon

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease, and its prevalence is increasing with age. A wealth of genetic evidence indicates that the endo-lysosomal system is a major pathway driving PD pathogenesis with a growing number of genes encoding endo-lysosomal proteins identified as risk factors for PD, making it a promising target for therapeutic intervention. However, detailed knowledge and understanding of the molecular mechanisms linking these genes to the disease are available for only a handful of them (e.g. LRRK2, GBA1, VPS35). Taking on the challenge of studying poorly characterized genes and proteins can be daunting, due to the limited availability of tools and knowledge from previous literature. This review aims at providing a valuable source of molecular and cellular insights into the biology of lesser-studied PD-linked endo-lysosomal genes, to help and encourage researchers in filling the knowledge gap around these less popular genetic players. Specific endo-lysosomal pathways discussed range from endocytosis, sorting, and vesicular trafficking to the regulation of membrane lipids of these membrane-bound organelles and the specific enzymatic activities they contain. We also provide perspectives on future challenges that the community needs to tackle and propose approaches to move forward in our understanding of these poorly studied endo-lysosomal genes. This will help harness their potential in designing innovative and efficient treatments to ultimately re-establish neuronal homeostasis in PD but also other diseases involving endo-lysosomal dysfunction.

Relationship between polymorphism of receptor SCARB2 gene and clinical severity of enterovirus-71 associated hand-foot-mouth disease

BACKGROUND

To investigate the relationship between polymorphism of scavenger receptor class B member 2 (SCARB2) gene and clinical severity of enterovirus (EV)-71 associated hand-foot-mouth disease (HFMD).

METHODS

Among the 100 recruited cases, 56 were in the severe HFMD group (case group) and 44 were in the general HFMD group (control group). By screening functional single nucleotide polymorphisms (SNPs) and hot SNPs, and performing SNP site optimization, some SNP sites of SCARB2 gene were selected for analysis. Genotyping was performed using a MassArray platform. PLINK software was used for statistical processing and analysis of the correlation differences between the mutant genotypes in the severe and general HFMD groups. The relationship between the SNPs and clinical severity of enterovirus (EV)-71 associated HFMD was assessed.

RESULTS

28 SNPs in SCARB2 were selected by site optimization. Then three loci were not in agreement with the minor allele frequency (MAF) in the 1000 Han Chinese in Beijing (CHB) dataset. Another three loci could not be detected. Nine loci were not suitable for further analysis (MAF < 0.01 and Hardy-Weinberg [HWE] P < 0.001). A total of 13 sites were subsequently analyzed. Through Fisher analysis, the frequency of the rs6812193 T allele was 0.134 and 0.034 in the severe and general HFMD groups, respectively (P 0.023 < 0.05, odds ratio [OR] 4.381 > 1). Logistic regression analysis of rs6812193 T alleles between the severe and general HFMD groups, respectively (P 0.023 < 0.05, OR 4.412 > 1, L95 1.210 > 1). Genotype logistic regression analysis of the rs6812193 alleles CT + TT versus CC gave an OR of 4.56 (95% confidence interval [95% CI] 1.22-17.04, P = 0.012).

CONCLUSION

The rs6812193 T allele was a susceptibility SNP for SHFMD, and the rs6812193 polymorphism might be significantly associated with the susceptibility to EV-71 infection.

Genetics variants and expression of the SCARB2 gene in the pathogenesis of Parkinson's disease in Russia

Lysosomal integral membrane protein-2 (LIMP-2), encoded by the SCARB2 gene, is the specific lysosomal receptor for glucocerebrosidase enzyme. Association between rs6812193 and rs68250047 of SCARB2 with PD has been shown in genetic studies, including large genome-wide association studies. The aim of the current study was to determine whether rs6812193 and rs8475 are associated with PD in Russia. rs6812193 and rs8475 were genotyped in a total of 604 PD patients (65 PD patients with positive (fPD) and 539 PD patients with negative family history (sPD)) and 413 controls and also in 17 patients with PD associated with GBA mutations (PD-GBA) and 18 asymptomatic GBA mutation carriers (GBA-Carriers). SCARB2 expression was measured by real-time PCR in CD45+ blood cells in part of individuals in the studied groups. No linkage disequilibrium was shown between rs6812193 and rs8475 in Russian population. Increased PD risk for TT variant of rs8475 (OR = 2.02; p < 0.001) was found in sPD patients but not in fPD. rs6812193 and rs8475 were not associated with age at onset (AAO) of PD. SCARB2 expression level was decreased in GBA-PD patients and GBA-Carriers compared to PD patients (padjusted = 0.02, padjusted = 0.003, respectively) and GBA-Carriers compared to controls (padjusted = 0.013) with no significant difference in PD patients and controls. SCARB2 expression was not modified with rs6812193 and rs8475. In conclusion, rs8475 was associated with PD status. rs6812193 and rs8475 are not genetic modifier of AAO of PD and do not influence on SCARB2 mRNA level in CD45+ blood cells in studied groups. SCARB2 expression could be modified with GBA mutations and is independent of PD status.

SCARB2 variants and glucocerebrosidase activity in Parkinson's disease

Mutations in glucocerebrosidase (GBA) are a common risk factor for Parkinson's disease (PD). The scavenger receptor class B member 2 (SCARB2) gene encodes a receptor responsible for the transport of glucocerebrosidase (GCase) to the lysosome. Two common SNPs in linkage disequilibrium with SCARB2, rs6812193 and rs6825004, have been associated with PD and Lewy Body Disease in genome-wide association studies. Whether these SNPs are associated with altered glucocerebrosidase enzymatic activity is unknown. Our objective was to determine whether SCARB2 SNPs are associated with PD and with reduced GCase activity. The GBA gene was fully sequenced, and the LRRK2 G2019S and SCARB2 rs6812193 and rs6825004 SNPs were genotyped in 548 PD patients and 272 controls. GCase activity in dried blood spots was measured by tandem mass spectrometry. We tested the association between SCARB2 genotypes and PD risk in regression models adjusted for gender, age, and LRRK2 G2019S and GBA mutation status. We compared GCase activity between participants with different genotypes at rs6812193 and rs6825004. Genotype at rs6812193 was associated with PD status. PD cases were less likely to carry the T allele than the C allele (OR=0.71; P=0.004), but GCase enzymatic activity was similar across rs6812193 genotypes (C/C: 11.88 μmol/l/h; C/T: 11.80 μmol/l/h; T/T: 12.02 μmol/l/h; P=0.867). Genotype at rs6825004 was not associated with either PD status or GCase activity. In conclusion, our results support an association between SCARB2 genotype at rs6812193 and PD, but suggest that the increased risk is not mediated by GCase activity.

No association of FAM47E rs6812193, SCARB2 rs6825004 and STX1B rs4889603 polymorphisms with Parkinson's disease in a Chinese Han population

Recently, a series of studies found that the single-nucleotide polymorphisms (SNPs) rs6812193 in the family with sequence similarity 47, member E (FAM47E), rs6825004 in the scavenger receptor class B member 2 (SCARB2) and rs4889603 in the Syntaxin1B (STX1B) genes increase the risk for Parkinson's disease (PD). However, the results of subsequent independent studies were inconsistent. To explore the associations between the three SNPs and PD in the Chinese population, a large cohort was analyzed in a case-control study. A total of 1994 subjects, including 1179 PD and 815 healthy controls (HCs), were investigated. All subjects were genotyped for rs6812193, rs6825004 and rs4889603 using the Sequenom iPLEX Assay. There was no significant difference in additive genetic model of rs6812193, rs6825004 and rs4889603 between PD and controls, even after being stratified by sex and age. In addition, no significant differences were found between other subgroups of PD patients with regard to clinical presentation. Our findings suggested that FAM47E rs6812193, SCARB2 rs6825004 and STX1B rs4889603 do not confer a significant risk for PD in Chinese population.

Association between rs6812193 polymorphism and sporadic Parkinson's disease susceptibility

Recently, the association of a single nucleotide polymorphism rs6812193 C/T with sporadic Parkinson's disease (PD) susceptibility has been widely evaluated, but the results remained inconsistent. This association should be clarified because of the importance of it on human health and quality of life. We performed a comprehensive meta-analysis to evaluate the association between the rs6812193 polymorphism and sporadic PD. PubMed was used to retrieve articles published up to June 2014 for all studies evaluating the rs6812193 polymorphism and PD in humans. Ethnicity-specific subgroup analysis was also performed based on ethnicity susceptibility. A total of 17 independent study samples (15 Caucasians and 2 Asians) including 17,956 cases and 52,751 controls were used in the presented study. The MAFT (minor allele T frequency) in PD patients of European descent is obviously higher than Asian cases (p < 0.01). The results suggested the rs6812193 polymorphism (allele T vs. C) is significantly associated with PD susceptibility among overall samples (OR 0.882, 95 % CI 0.856-0.908) and Caucasian population (OR 0.881, 95 % CI 0.856-0.907), but not in Asian samples (OR 0.918, 95 % CI 0.721-1.168). No evidence of publication bias was observed. Throughout our analysis, the rs6812193 polymorphism is significantly associated with sporadic PD susceptibility in Caucasian samples, and ethnicity might be the key point of inconsistency in rs6812193 studies. Further studies are warranted to re-examine the observed associations, especially in different ethnicities.