title: Mutations and CpG islands among hepatitis B virus genotypes in Europe.
abstract: BACKGROUND
  Hepatitis B virus (HBV) genotypes have a distinct geographical distribution and influence disease progression and treatment outcomes. The purpose of this study was to investigate the distribution of HBV genotypes in Europe, the impact of mutation of different genotypes on HBV gene abnormalities, the features of CpG islands in each genotype and their potential role in epigenetic regulation.
  
  
  RESULTS
  Of 383 HBV isolates from European patients, HBV genotypes A-G were identified, with the most frequent being genotype D (51.96%) in 12 countries, followed by A (39.16%) in 7 countries, and then E (3.66%), G (2.87%), B (1.57%), F (0.52%) and C (0.26%). A higher rate of mutant isolates were identified in those with genotype D (46.7%) followed by G (45.5%), and mutations were associated with structural and functional abnormalities of HBV genes. Conventional CpG island I was observed in genotypes A, B, C, D and E. Conventional islands II and III were detected in all A-G genotypes. A novel CpG island IV was found in genotypes A, D and E, and island V was only observed in genotype F. The A-G genotypes lacked the novel CpG island VI. "Split" CpG island I in genotypes D and E and "split" island II in genotypes A, D, E, F and G were observed. Two mutant isolates from genotype D and one from E were found to lack both CpG islands I and III.
  
  
  CONCLUSIONS
  HBV genotypes A-G were identified in European patients. Structural and functional abnormalities of HBV genes were caused by mutations leading to the association of genotypes D and G with increased severity of liver disease. The distribution, length and genetic traits of CpG islands were different between genotypes and their biological and clinical significances warrant further study, which will help us better understand the potential role of CpG islands in epigenetic regulation of the HBV genome.
authors: Faculty of Science and Engineering, University Paul Sabatier, Toulouse, 31062, France. chengyao.zhong@gmail.com.
authors: Chengyao
authors: C
authors: Zhong
authors: Key Laboratory of Birth Defects and Reproductive Health of National Health and Family Planning Commission, Chongqing Research Institute for Population and Family Planning Science and Technology, Chongqing, 400020, China. desonny@163.com.
authors: Zhiwei
authors: Z
authors: Hou
authors: Jinxin Research Institute for Reproductive Medicine and Genetics, Chengdu Jinjiang Hospital for Maternal and Child Health Care, Chengdu, 610066, China. en_huang@sina.cn.
authors: Jihua
authors: J
authors: Huang
authors: Research Center for Reproductive Medicine, Shantou University Medical College, Shantou, 515041, China. qdxie@stu.edu.cn.
authors: Qingdong
authors: Q
authors: Xie
authors: Jinxin Research Institute for Reproductive Medicine and Genetics, Chengdu Jinjiang Hospital for Maternal and Child Health Care, Chengdu, 610066, China. yzhong2014@126.com.
authors: Ying
authors: Y
authors: Zhong
mesh_terms: D018899:CpG Islands / Q000235:genetics*; D019175:DNA Methylation; D044127:Epigenesis, Genetic / Q000235:genetics*; D005060:Europe; D016679:Genome, Viral; D005838:Genotype; D006509:Hepatitis B / Q000821:virology*; D006515:Hepatitis B virus / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D009154:Mutation / Q000235:genetics*
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