Down-Regulation of H3K4me3 by MM-102 Facilitates Epigenetic Reprogramming of Porcine Somatic Cell Nuclear Transfer Embryos

Abstract

Background/Aims: Aberrantly high levels of H3K4me3, caused by incomplete epigenetic reprogramming, likely cause a low efficiency of somatic cell nuclear transfer (SCNT). Smal molecule inhibitors aimed at epigenetic modification can be used to improve porcine SCNT embryo development. In this study, we examined the effects of MM-102, an H3K4 histone methyltransferase inhibitor, on porcine SCNT preimplantation embryos to investigate the mechanism by which H3K4 methylation regulated global epigenetic reprograming during SCNT. Methods: MM-102 was added to the SCNT embryos culture system and the global levels of various epigenetic modifications were measured by immunofluorescence (IF) staining and were quantified by Image J software. Relative genes expression levels were detected by quantitative real-time PCR. Results: MM-102 (75 μM) treatment reduced global H3K4, H3K9 methylation and 5mC levels especially at the zygotic gene activation (ZGA) and blastocyst stages. MM-102 treatment mainly down-regulated a series of DNA and histone methyltransferases, and up-regulated a number of hitone acetyltransferases and transcriptional activators. Furthermore, MM-102 treatment positively regulated the mRNA expression of genes related to pluripotency (OCT4, NANOG, CDX2) and apoptosis (BCL2). Conclusion: Down-regulation of H3K4me3 with MM-102 rescued aberrant gene expression patterns of a series of epigenetic chromatin modification enzymes, pluripotent and apoptotic genes at the ZGA and blastocyst stages, thereby greatly improving porcine SCNT efficiency and blastocyst quality, making them more similar to in vivo embryos (IVV).