Exogenous expression of OCT4 facilitates oocyte-mediated reprogramming in cloned porcine embryos

OCT4 is a well-established regulator of pluripotency and nuclear reprogramming. To determine if improving OCT4 abundance can facilitate oocyte-mediated reprogramming in cloned porcine embryos, we artificially increased OCT4 levels by co-incubating donor cells with 50 ng/µl OCT4 plasmid. We observed higher rates of blastocyst formation (P < 0.05) and lower levels of blastocyst apoptosis in nuclear-transfer-derived embryos carrying OCT4-incubated donor nuclei (OCT4-SCNT). The beneficial effect caused by exogenous expression of OCT4 involves epigenetic changes, wherein increased histone acetylation (AcH3K9) appeared in OCT4-SCNT embryos at the one-cell and blastocyst stages and reduced histone methylation (H3K9me2) was observed at the one-cell stage (P < 0.05). There was a transient increase in exogenous OCT4 and an up-regulation of endogenous OCT4 level in OCT4-SCNT embryos (P < 0.05), while the expression pattern of epigenetic enzymes was changed. These modifications were accompanied by an up-regulation of CDX2, whose interaction with OCT4 is instrumental for implantation, and a down-regulation of XIST, a negative indicator of reprogramming (P < 0.05). Taken together, our results support a role for exogenous expression of OCT4 in improving the efficiency of nuclear reprogramming while establishing a convenient and timesaving method to improve nuclear-transfer outcomes.