Methylation profiling in individuals with uniparental disomy identifies novel differentially methylated regions on chromosome 15

  1. Stylianos E. Antonarakis1
  1. 1 Department of Genetic Medicine and Development, University of Geneva, Geneva 1211, Switzerland;
  2. 2 Swiss Institute of Bioinformatics, Lausanne 1015, Switzerland;
  3. 3 Institute of Medical Genetics, University of Zurich, Zurich 8603, Switzerland;
  4. 4 Wessex Regional Genetics Laboratory, Salisbury SP2 8BJ, United Kingdom;
  5. 5 Human Genetics Division, Southampton University School of Medicine, Southampton SO16 6YD, United Kingdom;
  6. 6 Department of Pathology, Seconda Universita' di Napoli, Naples 80138, Italy;
  7. 7 Department of Gynaecology, Obstetrics and Reproductive Medicine, Seconda Universita' di Napoli, Naples 80138, Italy;
  8. 8 Department of Human Genetics, University Medical Center Nijmegen, Nijmegen 6525GA, The Netherlands
    • 9 Present address: Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, NY 10029, USA.

    Abstract

    The maternal and paternal genomes possess distinct epigenetic marks that distinguish them at imprinted loci. In order to identify imprinted loci, we used a novel method, taking advantage of the fact that uniparental disomy (UPD) provides a system that allows the two parental chromosomes to be studied independently. We profiled the paternal and maternal methylation on chromosome 15 using immunoprecipitation of methylated DNA and hybridization to tiling oligonucleotide arrays. Comparison of six individuals with maternal versus paternal UPD15 revealed 12 differentially methylated regions (DMRs). Putative DMRs were validated by bisulfite sequencing, confirming the presence of parent-of-origin-specific methylation marks. We detected DMRs associated with known imprinted genes within the Prader-Willi/Angelman syndrome region, such as SNRPN and MAGEL2, validating this as a method of detecting imprinted loci. Of the 12 DMRs identified, eight were novel, some of which are associated with genes not previously thought to be imprinted. These include a site within intron 2 of IGF1R at 15q26.3, a gene that plays a fundamental role in growth, and an intergenic site upstream of GABRG3 that lies within a previously defined candidate region conferring an increased maternal risk of psychosis. These data provide a map of parent-of-origin-specific epigenetic modifications on chromosome 15, identifying DNA elements that may play a functional role in the imprinting process. Application of this methodology to other chromosomes for which UPD has been reported will allow the systematic identification of imprinted sites throughout the genome.

    Footnotes

    • Received March 31, 2010.
    • Accepted June 16, 2010.
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