title: CpG methylation patterns of human mitochondrial DNA.
abstract: The epigenetic modification of mitochondrial DNA (mtDNA) is still in controversy. To clarify this point, we applied the gold standard method for DNA methylation, bisulfite pyrosequencing, to examine human mtDNA methylation status. Before bisulfite conversion, BamHI was used to digest DNA to open the loop of mtDNA. The results demonstrated that the linear mtDNA had significantly higher bisulfite conversion efficiency compared with circular mtDNA. Furthermore, the methylation values obtained from linear mtDNA were significantly lower than that of circular mtDNA, which was verified by SEQUENOM MassARRAY. The above impacts of circular structure were also observed in lung DNA samples but not in saliva DNA samples. Mitochondrial genome methylation of blood samples and saliva samples from 14 unrelated individuals was detected. The detected regions covered 83 CpG sites across mtDNA including D-loop, 12 S rRNA, 16 S rRNA, ND1, COXI, ND3, ND4, ND5, CYTB. We found that the average methylation levels of nine regions were all less than 2% for both sample types. In conclusion, our findings firstly show that the circular structure of mtDNA affects bisulfite conversion efficiency, which leads to overestimation of mtDNA methylation values. CpG methylation in human mtDNA is a very rare event at most DNA regions.
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, No. 361 Zhong Shan Road, Shijiazhuang, Hebei 050017, People's Republic of China.
authors.forename: Baojing
authors.initials: B
authors.lastname: Liu
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, No. 361 Zhong Shan Road, Shijiazhuang, Hebei 050017, People's Republic of China.
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Du
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, No. 361 Zhong Shan Road, Shijiazhuang, Hebei 050017, People's Republic of China.
authors.forename: Lu
authors.initials: L
authors.lastname: Chen
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, No. 361 Zhong Shan Road, Shijiazhuang, Hebei 050017, People's Republic of China.
authors.forename: Guangping
authors.initials: G
authors.lastname: Fu
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, No. 361 Zhong Shan Road, Shijiazhuang, Hebei 050017, People's Republic of China.
authors.forename: Shujin
authors.initials: S
authors.lastname: Li
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, No. 361 Zhong Shan Road, Shijiazhuang, Hebei 050017, People's Republic of China.
authors.forename: Lihong
authors.initials: L
authors.lastname: Fu
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, No. 361 Zhong Shan Road, Shijiazhuang, Hebei 050017, People's Republic of China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, No. 361 Zhong Shan Road, Shijiazhuang, Hebei 050017, People's Republic of China.
authors.forename: Chunling
authors.initials: C
authors.lastname: Ma
authors.affiliation: Hebei Key Laboratory of Forensic Medicine, Department of Forensic Medicine, Hebei Medical University, No. 361 Zhong Shan Road, Shijiazhuang, Hebei 050017, People's Republic of China.
authors.forename: Cong
authors.initials: C
authors.lastname: Bin
mesh_terms: D018899:CpG Islands; D019175:DNA Methylation; D004272:DNA, Mitochondrial / Q000235:genetics*; D044127:Epigenesis, Genetic; D006801:Humans
chemical_list: D004272:DNA, Mitochondrial