This study aimed to produce high-quality blastocysts and establish appropriate microinjection conditions for the introduction of target gene. First, we identified embryo development to the blastocyst stage after microinjection using the CRISPR/Cas9 system on the Cas9 protein or mRNA. As a result, we confirmed that blastocyst development in the Cas9 mRNA injected group significantly increased when compared to the Cas9 protein injected group (p<0.05). However, the blastocyst gene targeting rate increased in the Cas9 protein injected group when compared to the Cas9 mRNA injected group (p<0.05). Next, we treated the injection medium with 10 μg/ml of cytochalasin B (CB), and the microinjected embryos were cultured in CR1-aa medium supplemented with 0.1 μM of melatonin (Mela). Consequently, the blastocyst formation rate significantly increased in the CB treated group (p<0.05). After microinjecting embryos with the CB treated injection medium, we investigated blastocyst formation and quality via Mela treatment. Consequently, the Mela treated group demonstrated significantly increased blastocyst formation rates when compared to the non-treated group (p<0.05). Furthermore, immunofluorescence assay using RAD51 (DNA repair detection protein) and H2AX139ph (DNA damage detection protein) showed an increase in RAD51 positive cells in Mela treated embryos. Therefore, we verified the improvement in knock-in efficiency in microinjected bovine embryos using Cas9 protein. These results also demonstrated that the positive effect of the CB and Mela treatments improved the embryonic developmental competence and blastocyst qualities in genetically-edited bovine embryos.

The increase in the meat quality and milk production of cows, which breed Korean Native Cow (KNC) and Holstein cow, is not improving reproductive efficiency. In this study, we examined the effect of interferon (IFN) supplementation on motility of frozen-thawed semen and pregnancy rate after artificial insemination of KNC and Holstein cow. In experiment 1, we investigated the effect of IFN-tau concentration (10,000 IU and 20,000 IU) on the percentage of total motility (TM) and progressive motility (PM) of frozen-thawed spermatozoa. In experiment 2, KNC were infused 20,000 IU IFN-tau at insemination or after insemination. In experiment 3, KNC or Holstein cow were inseminated with frozen-thawed semen and infused 20,000 IU IFN-gamma or -tau after insemination. In experiment 1, the average of TM (23.9% to 30.9%) and PM (18.5% to 21.9%) were similar between control and treatments. In experiment 2, the pregnancy rates of IFN infusing times were not different from 45.8% to 53.6%. In experiment 3, the pregnancy rates of Holstein cow infused different kinds of IFN were similar (control, IFN-gamma, IFN-tau; 42.9%, 40.5%, 48.0%). In the case of KNC, however, the pregnancy rate of control was 55.6%, which was significantly lower than that of IFN-gamma (68.9%; p<0.05). Thus, IFN is effective on the improvement of reproductive efficiency, but further study is needed.