Is ART changing the epigenetic landscape of imprinting

Imprinted genes, which are epigenetically modified such that only a single parental allele is expressed, are often regulated by imprinting control regions (ICRs). ICRs typically are DNA methylated in the male or female germline and this DNA methylation is subsequently maintained, even when the genome is reprogrammed after fertilization. Many of the manipulations associated with Assisted Reproductive Technologies (ART) occur during periods of epigenetic reprogramming and it should, therefore, not be surprising that animal data show that loss of imprinting and loss of DNA methylation of ICRs is associated with procedures such as superovulation, in vitro fertilization and embryos culture and transfer. Less clear is whether there is an increase in loss of imprinting disorders associated with ART. Here we review the human and animal literature and discuss what it is necessary to address current controversies.