Inter- and Intra-Individual Variation in Allele-Specific DNA Methylation and Gene Expression in Children Conceived using Assisted Reproductive Technology

Abstract

Epidemiological studies have reported a higher incidence of rare disorders involving imprinted genes among children conceived using assisted reproductive technology (ART), suggesting that ART procedures may be disruptive to imprinted gene methylation patterns. We examined intra- and inter-individual variation in DNA methylation at the differentially methylated regions (DMRs) of the IGF2/H19 and IGF2R loci in a population of children conceived in vitro or in vivo. We found substantial variation in allele-specific methylation at both loci in both groups. Aberrant methylation of the maternal IGF2/H19 DMR was more common in the in vitro group, and the overall variance was also significantly greater in the in vitro group. We estimated the number of trophoblast stem cells in each group based on approximation of the variance of the binomial distribution of IGF2/H19 methylation ratios, as well as the distribution of X chromosome inactivation scores in placenta. Both of these independent measures indicated that placentas of the in vitro group were derived from fewer stem cells than the in vivo conceived group. Both IGF2 and H19 mRNAs were significantly lower in placenta from the in vitro group. Although average birth weight was lower in the in vitro group, we found no correlation between birth weight and IGF2 or IGF2R transcript levels or the ratio of IGF2/IGF2R transcript levels. Our results show that in vitro conception is associated with aberrant methylation patterns at the IGF2/H19 locus. However, very little of the inter- or intra-individual variation in H19 or IGF2 mRNA levels can be explained by differences in maternal DMR DNA methylation, in contrast to the expectations of current transcriptional imprinting models. Extraembryonic tissues of embryos cultured in vitro appear to be derived from fewer trophoblast stem cells. It is possible that this developmental difference has an effect on placental and fetal growth.

Primary epimutations introduced during intracytoplasmic sperm injection (ICSI) are corrected by germline-specific epigenetic reprogramming

“…Our results showed losses of methylation on the normally hypermethylated allele of imprinted genes but not gain of methylation on the normally hypomethylated allele in ART-generated offspring. These results are consistent with a study by Market-Velker et al (17) that analyzed offspring from mice subjected to ovarian stimulation, but contrast with the pattern of aberrant hypermethylation observed by Turan et al (18) in human tissues from offspring generated by ART.…”

Effect of sperm entry on blastocyst development after in vitro fertilization and intracytoplasmic sperm injection — mouse model

“…In human ART, concerns remain about whether fertilization techniques influence the distribution and expression of key transcription factors responsible for the developmental program of embryogenesis [7,22,51]. One of them, the POU-family transcription factor Oct4, is expressed throughout early embryonic development and becomes progressively restricted first to the entire inner cell mass (ICM) and then to the epiblast (EPI) at the blastocyst stage [35,46].…”

DOHaD et programmation pré- et péri-conceptionnelle

“…Outre l'atteinte métabolique, la mobilité spermatique Enfin, l'impact sur l'embryon des nouvelles procédures comme la maturation ovocytaire in vitro ou la vitrification ovocytaire 6 , n'a pas été évalué. [18,19]. Elles concernent des gènes impliqués dans des maladies métaboliques chroniques [42] et pourraient également être à l'origine de la diminution du développement trophoblastique et du poids foetal (IGF-2/H19, gènes soumis à l'empreinte [5]).…”

“…Le lien entre ces modifications épigénétiques et l'activation transcriptionnelle du génome embryonnaire n'est pas totalement élucidé. Toutefois, l'augmentation artificielle de l'acétylation des histones, comme l'inhibition de leur déméthyla-tion, perturbent l'activation du génome embryonnaire, montrant que la dynamique des modifications épigénétiques participe à cette [18,19]. Ces perturbations épigénétiques initiales, mémorisées par le génome embryonnaire, pourraient expliquer les effets de l'environnement de l'embryon préimplantatoire observés à long terme (voir plus loin).…”