title: Chromosome-wide mapping of DNA methylation patterns in normal and malignant prostate cells reveals pervasive methylation of gene-associated and conserved intergenic sequences.
abstract: BACKGROUND
  DNA methylation has been linked to genome regulation and dysregulation in health and disease respectively, and methods for characterizing genomic DNA methylation patterns are rapidly emerging. We have developed/refined methods for enrichment of methylated genomic fragments using the methyl-binding domain of the human MBD2 protein (MBD2-MBD) followed by analysis with high-density tiling microarrays. This MBD-chip approach was used to characterize DNA methylation patterns across all non-repetitive sequences of human chromosomes 21 and 22 at high-resolution in normal and malignant prostate cells.
  
  
  RESULTS
  Examining this data using computational methods that were designed specifically for DNA methylation tiling array data revealed widespread methylation of both gene promoter and non-promoter regions in cancer and normal cells. In addition to identifying several novel cancer hypermethylated 5' gene upstream regions that mediated epigenetic gene silencing, we also found several hypermethylated 3' gene downstream, intragenic and intergenic regions. The hypermethylated intragenic regions were highly enriched for overlap with intron-exon boundaries, suggesting a possible role in regulation of alternative transcriptional start sites, exon usage and/or splicing. The hypermethylated intergenic regions showed significant enrichment for conservation across vertebrate species. A sampling of these newly identified promoter (ADAMTS1 and SCARF2 genes) and non-promoter (downstream or within DSCR9, C21orf57 and HLCS genes) hypermethylated regions were effective in distinguishing malignant from normal prostate tissues and/or cell lines.
  
  
  CONCLUSIONS
  Comparison of chromosome-wide DNA methylation patterns in normal and malignant prostate cells revealed significant methylation of gene-proximal and conserved intergenic sequences. Such analyses can be easily extended for genome-wide methylation analysis in health and disease.
authors.affiliation: Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. syegnasu@jhmi.edu
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Yegnasubramanian
authors.forename: Zhijin
authors.initials: Z
authors.lastname: Wu
authors.forename: Michael C
authors.initials: MC
authors.lastname: Haffner
authors.forename: David
authors.initials: D
authors.lastname: Esopi
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Aryee
authors.forename: Raghav
authors.initials: R
authors.lastname: Badrinath
authors.forename: Tony L
authors.initials: TL
authors.lastname: He
authors.forename: James D
authors.initials: JD
authors.lastname: Morgan
authors.forename: Benilton
authors.initials: B
authors.lastname: Carvalho
authors.forename: Qizhi
authors.initials: Q
authors.lastname: Zheng
authors.forename: Angelo M
authors.initials: AM
authors.lastname: De Marzo
authors.forename: Rafael A
authors.initials: RA
authors.lastname: Irizarry
authors.forename: William G
authors.initials: WG
authors.lastname: Nelson
mesh_terms: D001483:Base Sequence; D014408:Biomarkers, Tumor / Q000235:genetics; D045744:Cell Line, Tumor; D002877:Chromosomes, Human / Q000235:genetics*; D017124:Conserved Sequence; D019175:DNA Methylation / Q000235:genetics*; D021901:DNA, Intergenic / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D008280:Magnetics; D008297:Male; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D015345:Oligonucleotide Probes / Q000235:genetics; D011467:Prostate / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology; D017434:Protein Structure, Tertiary
chemical_list: D014408:Biomarkers, Tumor; D021901:DNA, Intergenic; D004268:DNA-Binding Proteins; C115368:MBD2 protein; D015345:Oligonucleotide Probes