title: CpG islands or CpG clusters: how to identify functional GC-rich regions in a genome?
abstract: BACKGROUND
  CpG islands (CGIs), clusters of CpG dinucleotides in GC-rich regions, are often located in the 5' end of genes and considered gene markers. Hackenberg et al. (2006) recently developed a new algorithm, CpGcluster, which uses a completely different mathematical approach from previous traditional algorithms. Their evaluation suggests that CpGcluster provides a much more efficient approach to detecting functional clusters or islands of CpGs.
  
  
  RESULTS
  We systematically compared CpGcluster with the traditional algorithm by Takai and Jones (2002). Our comparisons of (1) the number of islands versus the number of genes in a genome, (2) the distribution of islands in different genomic regions, (3) island length, (4) the distance between two neighboring islands, and (5) methylation status suggest that Takai and Jones' algorithm is overall more appropriate for identifying promoter-associated islands of CpGs in vertebrate genomes.
  
  
  CONCLUSIONS
  The generation of genome sequence and DNA methylation data is expected to accelerate greatly. The information in this study is important for its extensive utility in gene feature analysis and epigenomics including gene prediction and methylation chip design in different genomes.
authors.affiliation: Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA 23298, USA. hanl2@vcu.edu
authors.forename: Leng
authors.initials: L
authors.lastname: Han
authors.forename: Zhongming
authors.initials: Z
authors.lastname: Zhao
mesh_terms: D000465:Algorithms; D000818:Animals; D018899:CpG Islands / Q000235:genetics*; D019175:DNA Methylation; D005819:Genetic Markers; D016678:Genome; D006801:Humans; D051379:Mice; D011401:Promoter Regions, Genetic
chemical_list: D005819:Genetic Markers