title: 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.
authors.affiliation: Department of Neurology and Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. Electronic address: rabbit82@gmail.com.
authors.forename: Yu-yan
authors.initials: YY
authors.lastname: Tan
authors.affiliation: Department of Neurology and Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. Electronic address: breezy51@163.com.
authors.forename: Li
authors.initials: L
authors.lastname: Wu
authors.affiliation: Department of Neurology and Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. Electronic address: san_pi_love@126.com.
authors.forename: Zong-bo
authors.initials: ZB
authors.lastname: Zhao
authors.affiliation: Department of Neurology and Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. Electronic address: wang-ying@medmail.com.cn.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Neurology and Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. Electronic address: xiaoqin67@medmail.com.cn.
authors.forename: Qin
authors.initials: Q
authors.lastname: Xiao
authors.affiliation: Department of Neurology and Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. Electronic address: jly0520@hotmail.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Neurology and Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. Electronic address: wgneuron@hotmail.com.
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Neurology and Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. Electronic address: mjf74@163.com.
authors.forename: Jian-fang
authors.initials: JF
authors.lastname: Ma
authors.affiliation: Department of Neurology and Institute of Neurology, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. Electronic address: chen_sd@medmail.com.cn.
authors.forename: Sheng-di
authors.initials: SD
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000378:metabolism; D001921:Brain / Q000378:metabolism / Q000473:pathology; D018899:CpG Islands / Q000502:physiology; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000502:physiology*; D005260:Female; D006801:Humans; D000071158:Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; D007962:Leukocytes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D051844:alpha-Synuclein / Q000235:genetics / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D051844:alpha-Synuclein; D004247:DNA; C495280:LRRK2 protein, human; D000071158:Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; D017346:Protein Serine-Threonine Kinases
keywords: DNA methylation; LRRK2; Parkinson's disease; SNCA