Chungbuk National University Cheongju-si/ Chungbuk national university, Ch'ungch'ong-bukto, Republic of Korea
Abstract: The phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway is known to be a key signaling pathway in various cell types, playing critical roles in cell proliferation, survival, and particularly in zygotic genome activation (ZGA) and anti-apoptosis. Although the role of the PI3K/AKT pathway in mouse embryonic development is well established, its function in porcine embryonic development remains unexplored. This study aimed to investigate the effects of the PI3K/AKT signaling pathway during preimplantation development in porcine embryos. We performed immunofluorescence to detect total and phosphorylated AKT (pAKT), as well as total and phosphorylated RPS6 (pRPS6), commonly used downstream markers of the PI3K/AKT pathway, throughout early development. Our results revealed that both AKT and pAKT were expressed during early embryonic development. Notably, pAKT translocated to the nucleus at the 2-cell stage, coinciding with minor ZGA, and was strongly expressed in the nucleus at the 4-cell stage during major ZGA. RPS6 and its phosphorylated form were localized in the cytoplasm, consistent with their role in translation. These results were consistent in embryos derived from both parthenogenetic activation (PA) and in vitro fertilization. Then, we treated early embryos with varying concentrations (0, 1, 10, and 100 µM) of LY294002, a PI3K inhibitor, during in vitro culture after PA. The cleavage rates were not significantly different, but the blastocyst formation rates were significantly decreased in 1 and 100 µM LY294002-treated groups compared to the control group. TUNEL assay revealed that total cell numbers in blastocysts decreased in a concentration-dependent manner with LY294002 treatment. While the number of apoptotic cells was not significantly different among groups, the apoptotic index was significantly increased in LY294002-treated groups. These findings demonstrate that the PI3K/AKT signaling pathway is essential for porcine preimplantation embryo development by regulating ZGA and apoptosis. Further studies will investigate the molecular mechanisms of PI3K/AKT signaling during ZGA.
Funding Source: “Technology Innovation Program funded by the MOTIE, Korea (20023068)”, and “IPET in Food, Agriculture, Forestry and Fisheries funded by MAFRA (RS-2024-00398561, RS-2024-00399475)", Republic of Korea.
