Genetic-epigenetic intersection in trophoblast differentiation: Implications for extraembryonic tissue function

DNA methylation in porcine preimplantation embryos developed in vivo and produced by in vitro fertilization, parthenogenetic activation and somatic cell nuclear transfer

“…51 A potential consequence of these aberrations may be deviant placentation resulting in placental abnormalities and associated embryonic loss, which is a frequent finding with SCNT in the pig. 29,52,53 Interestingly, 50 and 14% of SCNT early and late blastocysts, respectively, displayed a methylation level comparable to IV blastocysts, indicating that epigenomic reprogramming at SCNT is a stochastic phenomenon, 23,26,54,55 which may be associated with full term development. However, the lack of lineage-specific DNA methylation in SCNT IV-like late blastocysts hints the defective TE gene expression pattern putatively associated with placental abnormalities in cloned pigs.…”

Tracking the intermediate stages of epithelial-mesenchymal transition in epithelial stem cells and cancer

“…19,27 The main mechanisms of trophoblast epigenetic regulation include DNA methylation, histone modifications and X-chromosome inactivation. 46,47 In contrast to pluripotent embryonic stem cells responsible for the formation of the embryo, DNA of the trophoblast epigenome is hypomethylated. This hypomethylation is critical for implantation and trophoblast differentiation.…”

Is there a role for endogenous retroviruses to mediate long-term adaptive phenotypic response upon environmental inputs?

“…The H3K9 trimethylation-mediated silencing pathway might function to maintain the IAP elements in silenced state during this early developmental window when global DNA methylation is reprogrammed (reviewed in [37]). It is interesting to note that although the genomic DNA methylation levels remain constantly high in the embryo proper throughout development (once it is rewritten in the blastocyst), the extraembryonic tissues exhibit lower amount of DNA methylation, a phenomenon that appears to have a critical role in the embryonic and extraembryonic lineage commitment process (reviewed in [38]). Recent studies have further shed light on this issue by showing that the observed undermethylation in the extraembryonic lineage could be noted mostly in the intergenic and repeat regions, rather than displaying a pervasive pattern all over the genome [39].…”