Genome-wide DNA methylation patterns of bovine blastocysts derived from in vivo embryos subjected to in vitro culture before, during or after embryonic genome activation

Abstract

BackgroundAberrant DNA methylation patterns of genes required for development are common in in vitro produced embryos. In this regard, we previously identified altered DNA methylation patterns of in vivo developed blastocysts from embryos which spent different stages of development in vitro, indicating carryover effects of suboptimal culture conditions on epigenetic signatures of preimplantation embryos. However, epigenetic responses of in vivo originated embryos to suboptimal culture conditions are not fully understood. Therefore, here we investigated DNA methylation patterns of in vivo derived bovine embryos subjected to in vitro culture condition before, during or after major embryonic genome activation (EGA). For this, in vivo produced 2-, 8- and 16-cell stage embryos were cultured in vitro until the blastocyst stage and blastocysts were used for genome-wide DNA methylation analysis.ResultsThe 2- and 8-cell flushed embryo groups showed lower blastocyst rates compared to the 16-cell flush group. This was further accompanied by increased numbers of differentially methylated genomic regions (DMRs) in blastocysts of the 2- and 8-cell flush groups compared to the complete in vivo control ones. Moreover, 1623 genomic loci including imprinted genes were hypermethylated in blastocyst of 2-, 8- and 16-cell flushed groups, indicating the presence of genomic regions which are sensitive to the in vitro culture at any stage of embryonic development. Furthermore, hypermethylated genomic loci outnumbered hypomethylated ones in blastocysts of 2- and 16-cell flushed embryo groups, but the opposite occurred in the 8-cell group. Moreover, DMRs which were unique to blastocysts of the 2-cell flushed group and inversely correlated with corresponding mRNA expression levels were involved in plasma membrane lactate transport, amino acid transport and phosphorus metabolic processes, whereas DMRs which were specific to the 8-cell group and inversely correlated with corresponding mRNA expression levels were involved in several biological processes including regulation of fatty acids and steroid biosynthesis processes.ConclusionIn vivo embryos subjected to in vitro culture before and during major embryonic genome activation (EGA) are prone to changes in DNA methylation marks and exposure of in vivo embryos to in vitro culture during the time of EGA increased hypomethylated genomic loci in blastocysts.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4826-3) contains supplementary material, which is available to authorized users.

Extracellular Vesicles Function as Bioactive Molecular Transmitters in the Mammalian Oviduct: An Inspiration for Optimizing in Vitro Culture Systems and Improving Delivery of Exogenous Nucleic Acids during Preimplantation Embryonic Development

“…In addition, supplementation of IVC media with OVS also improved embryo development and cryosurvival [10,11]. Although suboptimal IVC conditions might lead to epigenetic effects on embryo developmental potential [83][84][85], supplementation of IVC media with OVS containing mRNAs linked to chromatin modification, such as histone methyltransferases, histone demethylases or DNA methyltransferase, will also partly revert the abnormal epigenetic modifications [13]. Thus, adding OVS into IVC media could deliver a cocktail of specific bioactive molecule into embryos and mimic the communication between oviductal epithelium and embryos and overcome the deficiencies in IVC systems.…”

Mitochondria in early development: linking the microenvironment, metabolism and the epigenome

“…The amino acid methionine is the precursor of the universal methyl donor S-adenosylmethionine (SAM), catalysed by methionine adenosyltransferases (MATs), that acts as a co-factor in methylation reactions (Finkelstein 1990). Methionine has been found to be essential for mouse and bovine blastocyst formation, as omission of methionine from culture reduces mouse blastocyst formation, and morula and blastocyst H3K4me3 (Sun et al 2018), while addition of the methionine antagonist ethionine following embryonic genome activation (EGA) impairs blastocyst development and cell number (Menezo et al 1989, Ikeda et al 2012, Kudo et al 2015 accompanied by a reduction in H3K9me3 modification of Nanog and Tead4 (Kudo et al 2015). Importantly, this loss in developmental potential coincides with the increase in SAM synthesis that occurs following compaction (Menezo et al 1989), suggesting a requirement for appropriate metabolite availability at the time of EGA.…”

Maturação oocitária: Eventos que suportam etapas subsequentes do desenvolvimento

“…Metabolism in the oocyte is characterized by transcription and active translation during the pre-ovulatory period. However, gene transcription ceases before ovulation, so the oocyte, zygote, and embryo (Figure 3), with less than 16 blastomeres (bovine), are dependent on the pool of mRNAs and proteins accumulated during the period of growth and maturation (Meirelles et al, 2004;Salilew-Wondim et al, 2018). Oocytes depend on the synthesis and activation of a variety of proteins so they can enter and continue the process of oocyte maturation (Soeda et al, 2013;Chen et al, 2016).…”