Methylation of α-synuclein and leucine-rich repeat kinase 2 in leukocyte DNA of Parkinson's disease patients

Abstract

Background: Recent studies highlight the role of DNA methylation in the pathogenesis of Parkinson's disease (PD). However, there is a paucity of studies exploring the role of blood-based DNA methylation in PD. We aimed to explore identifiable epigenetic biomarkers for PD by analyzing the methylation status of α-synuclein (SNCA) and leucine-rich repeat kinase 2 (LRRK2) in leukocytes.

Methods: Bisulfite Specific PCR-based Sequencing method was used for semi-quantitative detection of methylation status of CpG islands in SNCA and LRRK2 promoter regions. Bisulfite Specific Cloning-based Sequencing method was used for further quantitative examination of CpG-2 methylation of SNCA. mRNA level was also detected in leukocytes.

Results: Semi-quantitative detection showed that the methylation status of SNCA CpG-2 differed between PD patients and normal controls, while there was no difference in CpG-1 of SNCA or in LRRK2 promoter. Further quantitative analysis by clonal assay showed that the CpG-2 of SNCA was hypomethylated in PD patients compared with the normal control (5.90% versus 7.69%, P=0.034). Moreover, among the 14 CpG sites of CpG-2, the 2nd, 4th and 9th CpG sites were significantly hypomethylated in PD patients. In subgroups of PD, the methylation level decreased in the early-onset PD patients (P=0.001). RT-PCR examination showed that SNCA mRNA was increased in PD patients compared with normal control (P=0.003).

Conclusions: Our results indicated that the methylation level of SNCA CpG-2, especially that of the 2nd, 4th and 9th CpG sites in leukocytes might have great potential to be a useful and informative biomarker in PD diagnosis and treatment.

Keywords: DNA methylation; LRRK2; Parkinson's disease; SNCA.