DNA Methylation Analysis Of SNCA Gene In Peripheral Blood Of Patients With Sporadic Parkinson's Disease

Objective:SNCA is a pathogenic gene identified in rare familial PD, and over-expression of SNCA was suggested in the pathogenesis of familial PD as well as sporadic PD. Allele length variability in Rep1of SNCA modulates susceptibility to sporadic PD and affects SNCA expression levels in both brains and peripheral blood mononuclear cells (PBMCs) of patients with sporadic PD. DNA methylation in SNCA intron-1is also involved in the regulation of SNCA expression and hypomethylation of this region was observed in postmortem brains of patients with sporadic PD. In this study, we studied the methylation status of SNCA intron-1, SNCA mRNA levels and Rep1genotypes in PBMCs of sporadic PD patients and controls and explored the relationship between DNA methylation, mRNA expression and Rep1genotypes.Methods:Peripheral blood mononuclear cells (PBMCs) from65sporadic PD patients and63healthy controls were isolated by density gradient centrifugation; DNA methylation level of SNCA intron-1was determined by bisulfite sequencing; mRNA level of SNCA was meatured by real-time quantitative PCR; Rep1polymorphism was examined by direct sequencing.Results:Hypomethylation of SNCA intron-1was detected in PBMCs of PD patients (p=0.024). And DNA methylation levels were associated with Rep1alleles and genotypes. The longest allele (271bp) was associated with lower level of methylation, while the shortest allele (267bp) was associated with higher level of methylation. Genotype 271bp/271bp showed significantly lower methylation levels than genotype267bp/267bp and269bp/269bp (p=0.014and0.043respectively). No significant difference of SNCA mRNA level was observed between PD and controls (p=0.107), and no correlation was observed between SNCA mRNA level and methylation level of SNCA intron-1or Rep1polymorphism.