The effect of valproic acid on bovine oocyte maturation and early embryonic development in vitro

From genome to epigenome: Who is a predominant player in the molecular hallmarks determining epigenetic mechanisms underlying ontogenesis?

Genetic factors are one of the basic determinants affecting ontogenesis in mammals. Nevertheless, on the one hand, epigenetic factors have been found to exert the preponderant and insightful impact on the intracellular mechanistic networks related to not only initiation and suppression, but also up- and downregulation of gene expression in all the phases of ontogenetic development in a variety of mammalian species. On the other hand, impairments in the epigenetic mechanisms underlying reprogramming of transcriptional activity of genes (termed epimutations) not only give rise to a broad spectrum of acute and chronic developmental abnormalities in mammalian embryos, foetuses and neonates, but also contribute to premature/expedited senescence or neoplastic transformation of cells and even neurodegenerative and mental disorders. The current article is focused on the unveiling the present knowledge aimed at the identification, classification and characterization of epigenetic agents as well as multifaceted interpretation of current and coming trends targeted at recognizing the epigenetic background of proper ontogenesis in mammals. Moreover, the next objective of this paper is to unravel the mechanistic insights into a wide array of disturbances leading to molecular imbalance taking place during epigenetic reprogramming of genomic DNA. The above-indicated imbalance seems to play a predominant role in the initiation and progression of anatomo-, histo-, and physiopathological processes throughout ontogenetic development. Conclusively, different modalities of epigenetically assisted therapeutic procedures that have been exemplified in the current article, might be the powerful and promiseful tools reliable and feasible in the medical treatments of several diseases triggered by dysfunctions in the epigenetic landscapes, e.g., myelodysplastic syndromes or epilepsy.

Histone deacetylase inhibitor during in vitro maturation decreases developmental capacity of bovine oocytes

This study aimed to evaluate the effect of scriptaid during pre-maturation (PIVM) and/or maturation (IVM) on developmental competence of bovine oocytes. Cumulus-oocyte complexes (COCs) were submitted to PIVM for 6 h in the presence or absence of scriptaid. COCs were distributed into five groups: T1-IVM for 22 h, T2-PIVM for 6 h and IVM for 22 h, T3-PIVM with scriptaid for 6 h and IVM for 22 h, T4-PIVM for 6 h and IVM with scriptaid for 22 h, and T5-PIVM with scriptaid for 6 h and IVM with scriptaid for 22 h. Nuclear maturation, gene expression, cumulus cells (CCs) expansion, and embryo development and quality were evaluated. At the end of maturation, all groups presented the majority of oocytes in MII (P>0.05). Only HAT1 gene was differentially expressed (P<0.01) in oocytes with different treatments. Regarding embryo development at D7, T4 (23%) and T5 (18%) had lower blastocyst rate (P<0.05) than the other treatments (T1 = 35%, T2 = 37% and T3 = 32%). No effect was observed when scriptaid in PIVM was used in less competent oocytes (P>0.05). In conclusion, presence of scriptaid in PIVM and/or IVM did not improve developmental competence or embryo quality.

Activation-induced cytidine deaminase selectively catalyzed active DNA demethylation in pluripotency gene and improved cell reprogramming in bovine SCNT embryo

DNA methylation in mammals is an epigenetic marker and necessary for normal embryogenesis. The global genomic demethylation of 5-methylcytosine occurs during the first cell cycle following fertilization. Activation-induced cytidine deaminase (AID), which is well-known for the function in antibody diversification, has been implicated to play a role in active demethylation, but its role in cell reprogramming and its crosstalk with other DNA demethylation mechanism need to be clarified. In this study, the dynamic epigenetic regulation of cell pluripotency and embryo development by AID in bovine preimplantation embryos was investigated. The analysis of an AID overexpressing transgenic cell line showed that AID overexpression did not change the global genomic methylation but did change the methylation status of the promoters of the OCT4, NANOG and SOX2 genes, thereby causing changes in their expression. The siRNA-mediated AID knockdown in early embryonic development indicated that AID interference did not affect oocyte maturation or the following embryo development after in vitro fertilization but influenced the DNA methylation status of OCT4 and NANOG. To clarify the role of AID in preimplantation embryos, SCNT embryos were obtained using AID-overexpressing cells as nuclear donors. Compared to the control group, the cleavage and blastocyst rates were both significantly improved in the AID-overexpression group. The expression of OCT4 and NANOG was increased in the SCNT embryos, whereas the methylation levels of their promoters were reduced. In conclusion, this study demonstrated that AID selectively catalyzes DNA demethylation of pluripotency genes to play a role in regulation their expression, improves bovine SCNT embryo development by increased expression levels.

Epigenetic reprogramming of human lung cancer cells with the extract of bovine parthenogenetic oocytes

The tumour suppressor gene silencing and proto-oncogene activation caused by epigenetic alterations plays an important role in the initiation and progression of cancer. Re-establishing the balance between the expression of tumour suppressor genes and proto-oncogenes by epigenetic modulation is a promising strategy for cancer treatment. In this study, we investigated whether cancer cells can be epigenetically reprogrammed by oocyte extract. H460 human lung cancer cells were reversibly permeabilized and incubated with the extract of bovine parthenogenetic oocytes. Bisulphite sequencing showed that bovine parthenogenetic oocyte extract induced significant demethylation at the promoters of the tumour suppressor genes RUNX3 and CDH1, but not at the promoter of the oncogenic pluripotency gene SOX2. Chromatin immunoprecipitation showed that the histone modifications at RUNX3 and CDH1 promoters were modulated towards a transcriptionally activating state, while those at SOX2 promoter towards a transcriptionally repressive state. Correspondingly, bovine parthenogenetic oocyte extract reversed the epigenetic silencing of RUNX3 and CDH1, and repressed the expression of SOX2. At the functional level, proliferation, anchorage-independent growth, migration and invasion of H460 cells was strongly inhibited. These results indicate that bovine parthenogenetic oocyte extract changes the expression patterns of tumour suppressor and oncogenic genes in cancer cells by remodelling the epigenetic modifications at their promoters. Bovine parthenogenetic oocyte extract may provide a useful tool for epigenetically reprogramming cancer cells and for dissecting the epigenetic mechanisms involved in tumorigenesis.