title: Placental expression of imprinted genes varies with sampling site and mode of delivery.
abstract: Imprinted genes, which are monoallelically expressed by virtue of an epigenetic process initiated in the germline, are known to play key roles in regulating fetal growth and placental development. Numerous studies are investigating the expression of these imprinted genes in the human placenta in relation to common complications of pregnancy such as fetal growth restriction and preeclampsia. This study aimed to determine whether placental sampling protocols or other factors such as fetal sex, gestational age and mode of delivery may influence the expression of imprinted genes predicted to regulate placental signalling.
  
  
  METHODS
  Term placentas were collected from Caucasian women delivering at University Hospital of Wales or Royal Gwent Hospital within two hours of delivery. Expression of the imprinted genes PHLDA2, CDKN1C, PEG3 and PEG10 was assayed by quantitative real time PCR. Intraplacental gene expression was analysed (N = 5). Placental gene expression was compared between male (N = 11) and female (N = 11) infants, early term (N = 8) and late term (N = 10) deliveries and between labouring (N = 13) and non-labouring (N = 21) participants.
  
  
  RESULTS
  The paternally expressed imprinted genes PEG3 and PEG10 were resilient to differences in sampling site, fetal sex, term gestational age and mode of delivery. The maternally expressed imprinted gene CDKN1C was elevated over 2-fold (p < 0.001) in placenta from labouring deliveries compared with elective caesarean sections. In addition, the maternally expressed imprinted gene PHLDA2 was elevated by 1.8 fold (p = 0.01) in samples taken at the distal edge of the placenta compared to the cord insertion site.
  
  
  CONCLUSIONS
  These findings support the reinterpretation of existing data sets on these genes in relation to complications of pregnancy and further reinforce the importance of optimising and unifying placental collection protocols for future studies.
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Cardiff, Wales, CF10 3AX, UK.
authors.forename: A B
authors.initials: AB
authors.lastname: Janssen
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Cardiff, Wales, CF10 3AX, UK.
authors.forename: S J
authors.initials: SJ
authors.lastname: Tunster
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital Wales, Cardiff, Wales CF144XW, UK.
authors.forename: N
authors.initials: N
authors.lastname: Savory
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital Wales, Cardiff, Wales CF144XW, UK.
authors.forename: A
authors.initials: A
authors.lastname: Holmes
authors.affiliation: Department of Obstetrics and Gynaecology, Royal Gwent Hospital, Newport, Wales NP202UB, UK.
authors.forename: J
authors.initials: J
authors.lastname: Beasley
authors.affiliation: Department of Obstetrics and Gynaecology, Royal Gwent Hospital, Newport, Wales NP202UB, UK.
authors.forename: S A R
authors.initials: SA
authors.lastname: Parveen
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital Wales, Cardiff, Wales CF144XW, UK.
authors.forename: R J A
authors.initials: RJ
authors.lastname: Penketh
authors.affiliation: Cardiff School of Biosciences, Cardiff University, Cardiff, Wales, CF10 3AX, UK. Electronic address: JohnRM@Cardiff.ac.uk.
authors.forename: R M
authors.initials: RM
authors.lastname: John
mesh_terms: D000328:Adult; D051017:Apoptosis Regulatory Proteins; D050761:Cyclin-Dependent Kinase Inhibitor p57 / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins; D036861:Delivery, Obstetric / Q000379:methods*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D018392:Genomic Imprinting; D005865:Gestational Age; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000235:genetics* / Q000378:metabolism; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins; D012737:Sex Factors; D055815:Young Adult
chemical_list: D051017:Apoptosis Regulatory Proteins; D050761:Cyclin-Dependent Kinase Inhibitor p57; D004268:DNA-Binding Proteins; D051741:Kruppel-Like Transcription Factors; D009687:Nuclear Proteins; C432965:PEG10 protein, human; C490820:PEG3 protein, human; D011506:Proteins; D016601:RNA-Binding Proteins; C109277:TSSC3 protein
keywords: Delivery mode; Imprinted genes; Placenta; Sampling