Epigenetic reduction OF H3K9me3 and H3K27me3 by RK-701 and GSK 126 improves the developmental competence of bovine SCNT embryos.
Somatic cell nuclear transfer (SCNT) failure has largely been attributed to incomplete epigenetic reprogramming, particularly the dysregulation of repressive histone modifications such as H3K9me3 and H3K27me3. Reducing these repressive marks has been shown to improve reprogramming efficiency in SCNT embryos. Although histone demethylase mRNA injection has been used for this purpose, it is labor-intensive, technically demanding, and time-consuming. In this study, we investigated a simplified approach that combined RK-701 and GSK-126 to reduce H3K9me3 and H3K27me3 levels, respectively, in bovine SCNT embryos. Three experimental groups were established: IVF embryos (control), SCNT-control (SCNT-C) embryos, and inhibitor-treated SCNT embryos (SCNT-T). The IVF group was used as a reference standard. Fused one-cell SCNT embryos were treated with 2 μM RK-701 and 0.2 μM GSK-126 from the one-cell stage to the 16-cell stage. Gene expression analysis at the 16-cell stage revealed a significant reduction in histone methyltransferase (HMT) expression (p < 0.05), and immunofluorescence analysis confirmed marked decreases in H3K9me3 and H3K27me3 levels. In addition, the expression of genes associated with zygotic genome activation (ZGA) and pluripotency was significantly higher in SCNT-T embryos than in SCNT-C embryos. Assessment of blastocyst quality revealed reduced reactive oxygen species (ROS) levels, decreased expression of apoptosis-related genes, and improved mitochondrial membrane potential in the treated group, as indicated by JC1 staining. Overall, this approach effectively reduced repressive histone marks, enhanced epigenetic reprogramming, and improved ZGA, thereby increasing the developmental rate and adhesion potential of bovine SCNT embryos. These findings suggest that combined treatment with RK-701 and GSK-126 may provide a simple and practical strategy for improving the efficiency of bovine cloning.