Epigenetic Reprogramming in Mammalian Develop-ment

Epigenetic modifications established during gametogenesis reg-ulate transcription and other nuclear processes in gametes, but also have influences in the zygote, embryo and postnatal life. The best-studied epigenetic modification is DNA methylation, which established at discrete regions of the oocyte and sperm genomes and governs genomic imprinting. Genomic imprint-ing is referred to an allele-specific methylation marking pro-cess that causes a sex-dependent monoallelic expression. These methylation marks remain on the paternal and maternal alleles into the next generation as a lifelong memory of parental origin. DNA methylation undergoes dramatic reprogramming after fer-tilization. The impairment of DNA methylation reprogramming behind assisted reproductive technologies (ART) and the rec-ognition of most vulnerable sequence elements are new debat-ing topics. Some studies showed the effect of culture media, ovarian stimulation or embryo transfer on the methylation pat-tern of embryos emphasizing the need to face ART-associated defects and search for strategies to mitigate adverse effects on the health of ART-derived children.