The epigenetic control of transposable elements and imprinted genes in newborns is affected by the mode of conception: ART versus spontaneous conception without underlying infertility
Résumé
STUDY QUESTION
Do assisted reproductive technologies alter DNA methylation and/or transcription of transposable elements and imprinted genes in cord blood and placenta?
SUMMARY ANSWER
After ART, DNA methylation and/or transcription changes of some transposable elements and imprinted genes were found in placenta samples while transcription modifications for some transposable elements were also discovered in cord blood.
WHAT IS KNOWN ALREADY
Recent studies have confirmed the increased risk of placenta-related adverse pregnancy outcomes and the excess of imprinted disorders with abnormal methylation patterns after ART, which raises the issue of a potential ART-induced epigenetic risk.
STUDY DESIGN, SIZE, DURATION
A total of 51 IVF/ICSI (15 conventional and 36 ICSI) singleton pregnancies were prospectively included from January 2013 to April 2015 and compared to 48 spontaneously conceived singleton pregnancies.
PARTICIPANTS/MATERIALS, SETTING, METHODS
The DNA methylation and transcription of three imprinted loci (H19/IGF2, KCNQ1OT1 and SNURF DMRs) and four transposon families (LINE-1, ERVFRD, AluYa5 and ERVW) in cord blood and placenta obtained at birth were assessed by pyrosequencing and quantitative RT-PCR, respectively. All data were adjusted for gestational age at delivery, sex of the newborn, parity and maternal age.
MAIN RESULTS AND THE ROLE OF CHANCE
DNA methylation levels of H19/IGF2, KCNQ1OT1, LINE-1Hs and ERVFRD-1 were significantly lower in IVF/ICSI placentas than in control placentas, while there was no difference for cord blood. Moreover, the expression of ERVFRD-1 and LINE-1 ORF2 in cord blood and ERVFRD-1 in placenta was lower in the IVF/ICSI group than in controls. The expression of ERVFRD-1 in placenta correlated positively with birth weight and placenta weight, but only in the control group, thus pointing to the potential deregulation of syncytin function after ART.
LARGE SCALE DATA
N/A.
LIMITATIONS, REASONS FOR CAUTION
The control group of fertile couples having conceived within 1 year prevented us from deciphering the distinct roles of ART and infertility.
WIDER IMPLICATIONS OF THE FINDINGS
These novel findings of ERVFRD (syncytin-2) expression correlating with birth weight and placenta weight suggest that more research on syncytins and pregnancy-associated diseases could lead to them being used as biomarkers or even as therapeutic targets. The epigenetic modifications in placenta for sequences involved in foetal development raise the question of their potential effects on pregnancy and future life. These results should encourage us to analyse the exact causes and consequences of epigenetic changes and strive to minimize these variations in the interests of epigenetic safety after ART.
STUDY FUNDING/COMPETING INTEREST(S)
The study was funded by a grant from Besançon and Dijon University Hospitals. The authors have no conflicts of interest to declare.