Abstract
Coenzyme Q10 is an important molecule for mitochondrial respiration and as an antioxidant. Maintenance of the ovum in a good condition is considered to be important for successful fertilization and development, which has been reported to be promoted by coenzyme Q10. In this study, we investigated the level of coenzyme Q10 during ovum fertilization and maturation. We attempted to analyze coenzyme Q10 levels during ovum development in species that use coenzyme Q10 but not coenzyme Q9. It was shown that medaka produces coenzyme Q10. We then measured the amount of coenzyme Q10 after fertilization of medaka ovum and found that it increased. The amount of free cholesterol biosynthesized from acetyl CoA as well as coenzyme Q10 increased during development, but the increase in coenzyme Q10 was more pronounced. The mRNA expression level of coq9 also increased during embryonic development, but the mRNA expression levels of other coenzyme Q10 synthases did not. These results suggest that the coq9 gene is upregulated during the development of medaka ovum after fertilization, resulting in an increase in the amount of coenzyme Q10 in the ovum. Medaka, which like humans has coenzyme Q10, is expected to become a model animal for coenzyme Q10 research.