We previously demonstrated that intracytoplasmic sperm injection (ICSI), a type of assisted reproductive technology (ART), can induce epimutations and/or epimutant phenotypes in somatic tissues of adult mice produced by this method. In the present study, we compared the occurrence of epimutations in mice produced by natural conception, ICSI and somatic cell nuclear transfer. Surprisingly, we observed the highest frequency of epimutations in somatic tissues from ICSI-derived mice. We also observed a delay in reprogramming of the maternal allele of the imprinted H19 gene in spermatogonia from juvenile ICSI-derived male mice. These observations led us to hypothesize that the exposure of the maternal gametic genome to exogenous gonadotropins during the endocrine stimulation of folliculogenesis (superovulation) may contribute to the disruption of the normal epigenetic programming of imprinted loci in somatic tissues and/or epigenetic reprogramming in the germ line of ensuing offspring. To test this hypothesis, we uncoupled superovulation from ICSI by subjecting female mice to gonadotropin stimulation and then allowing them to produce offspring by natural mating. We found that mice produced in this way also exhibited epimutations and/or epimutant phenotypes in somatic tissues and delayed epigenetic reprogramming in spermatogenic cells, providing evidence that gonadotropin stimulation contributes to the induction of epimutations during ART procedures. Our results suggest that gonadotropin stimulation protocols used in conjunction with ART procedures should be optimized to minimize the occurrence of epimutations in offspring produced by these methods.
The use of assisted reproductive technologies (ART) has become increasingly common worldwide and is now responsible for 2-3% of children born in developed countries. Multiple reports have suggested that ART-conceived children are more likely to develop rare epigenetic disorders such as Beckwith-Wiedemann Syndrome or Angelman Syndrome, both of which involve dysregulation of imprinted genes. Anecdotal reports suggest that animals produced with ART that manifest apparent epigenetic defects typically do not transmit these epimutations to subsequent generations when allowed to breed naturally, but this hypothesis has not been directly studied. We analyzed allele-specific DNA methylation and expression at three imprinted genes, H19, Snrpn, and Peg3, in somatic cells from adult mice generated with the use of intracytoplasmic sperm injection (ICSI), a type of ART. Epimutations were detected in most of the ICSI-derived mice, but not in somatic cells of their offspring produced by natural mating. We examined germ cells from the ICSI mice that exhibited epimutations in their somatic cells and confirmed normal epigenetic reprogramming of the three imprinted genes analyzed. Collectively, these results confirm that ART procedures can lead to the formation of primary epimutations, but while such epimutations are likely to be maintained indefinitely in somatic cells of the ART-derived individuals, they are normally corrected in the germ line by epigenetic reprogramming and thus, not propagated to subsequent generations.gametogenesis | transgenerational inheritance E arly embryos and germ cells are unique in that they must undergo extensive epigenetic reprogramming to reestablish developmental potency during each generation. This reprogramming entails erasure of most inherited epigenetic modifications followed by the acquisition and subsequent maintenance of new epigenetic profiles (1). Genomic imprinting is an epigenetic phenomenon found in eutherian and metatherian mammals (2) that results in parent-of-origin-specific, monoallelic expression of a subset of genes (3). This functional asymmetry of imprinted genes is conferred through differential DNA methylation patterns established during gametogenesis in each parent that distinguish the maternal and paternal alleles in the ensuing offspring (4, 5). These regions are known as differentially methylated regions (DMRs), and the differential methylation profiles at these genetic elements play an important role in regulating allele-specific expression of imprinted genes (3).Because the epigenome is distinct in each cell type and is readily reversible by developmental reprogramming, it is particularly susceptible to disruption by environmental influences (6). Such epigenetic defects are known as "epimutations" and can be of two types-primary epimutations or secondary epimutations (7). Primary epimutations result from a direct disruption of an epigenetic parameter such as DNA methylation that is then propagated through DNA replication to subsequent cells. Secondary epimutations result...
An imprint of resistance to HDM challenge in nonatopic, nonallergic adults was muted T-cell activation in the peripheral blood and inflammatory response in the nasal compartment, coupled with upregulation of genes that promote epidermal/epithelial cell barrier function.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.