LC3-Dependent Autophagy in Pig 2-Cell Cloned Embryos Could Influence the Degradation of Maternal mRNA and the Regulation of Epigenetic Modification

In this study, the distribution as well as the effect of autophagy on reprogramming in pig cloned embryos were observed immediately after somatic cell nuclear transfer. Results showed that the LC3 was at the highest level in cloned embryos at 2-cell stage, and it decreased with the development from 2-cell stage to blastocyst. Different to cloned embryos, the intensity of LC3 in parthenogenetic activation (PA) embryos was at the highest level at 4-cell stage. A markedly higher level of Bmp15, H1foo, and Dppa3 was shown in cloned embryos at 2-cell stage (p < 0.05 or p < 0.01), but a significantly lower level of LC3, Sox2, and eIF1A was observed at 4-cell stage (p < 0.05), compared with PA embryos. When the efficient interfering by the LC3 siRNA was performed on the cloned embryos (p < 0.01), not only the mRNA level of maternal Cyclin B, Bmp15, Gdf9, c-mos, H1foo, and Dppa3 was increased significantly (p < 0.05), but also the expression of Dnmt1 and Dnmt3b was obviously upregulated (p < 0.05). Although the expression of Sox2 and Oct4 is not changed, the expression of Stat3 decreased significantly (p < 0.05). Furthermore with the treatment of 200 nM rapamycin, the expression of eIF1A and Stat3 was significantly increased at 4-cell stage. In conclusion, the LC3-dependent autophagy mainly occurred in cloned embryos at 2-cell stage, but at 4-cell stage in PA embryos. In addition, the modulation of autophagy could affect genome activation by influencing the degradation of maternal mRNA and regulating the expression of DNA methyltransferase.