title: Decreased placental methylation at the H19/IGF2 imprinting control region is associated with normotensive intrauterine growth restriction but not preeclampsia.
abstract: Many genes exhibiting genomic imprinting, parent-of-origin differences in gene expression, are involved in regulating placental and fetal growth. The goal of the present study was to assess whether abnormal regulation of imprinted genes is associated with intrauterine growth restriction (IUGR) and/or preeclampsia (PET).
  
  
  METHODS
  Genomic DNA was extracted from at least two whole villi samples from control (N=22), IUGR (N=13), PET (N=17), and PET+IUGR (N=21) placentas. Methylation was assessed using the Illumina GoldenGate Methylation Cancer Panel I array and Pyrosequencing and MS-SNuPE assays.
  
  
  RESULTS
  The 11p15.5 ICR1 (associated with H19 and IGF2) methylation showed considerable intra-placental variability. Nonetheless, average methylation at this site was significantly decreased in normotensive IUGR placentas (p<0.001), but not in any other group. Methylation at ICR2 (KvDMR1; associated with CDKN1C and other maternally expressed 11p15.5 genes) was not significantly altered in any group and no significant changes in expression levels were observed in the genes controlled by this region. There were no significant methylation changes observed in any candidate imprinted gene evaluated by the Illumina array. LINE-1 methylation, a marker of whole genome methylation, was also similar in all groups.
  
  
  CONCLUSIONS
  Reduced methylation of ICR1 is associated with normotensive IUGR but not IUGR associated with preeclampsia, suggesting a different etiology of IUGR in this group. A reduction in placental IGF2 could be an adaptive response to restrict fetal growth in the presence of abnormal placentation or a response to poor fetal growth itself.
authors.affiliation: Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada.
authors.forename: D K
authors.initials: DK
authors.lastname: Bourque
authors.forename: L
authors.initials: L
authors.lastname: Avila
authors.forename: M
authors.initials: M
authors.lastname: Peñaherrera
authors.forename: P
authors.initials: P
authors.lastname: von Dadelszen
authors.forename: W P
authors.initials: WP
authors.lastname: Robinson
mesh_terms: D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D005260:Female; D005317:Fetal Growth Retardation / Q000235:genetics / Q000378:metabolism*; D018392:Genomic Imprinting; D006801:Humans; D007231:Infant, Newborn; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism*; D010920:Placenta / Q000378:metabolism*; D011225:Pre-Eclampsia / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA
chemical_list: C094335:H19 long non-coding RNA; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D007335:Insulin-Like Growth Factor II