Short communicationExpressions of the circadian genes Per2, Bmal1, Clock and Cry1 during the different stages of follicular development and their regulation by FSH in bovine granulosa cells from small follicles

Circadian clock genes are involved in mammalian reproductive physiology. We examined the expression of circadian clock genes such as Per2, Bmal1, Clock and Cry in granulosa cells from follicles at different developmental stages and in follicle-stimulating hormone (FSH)-treated granulosa cells. The expression of Clock mRNA was significantly increased in granulosa cells from pre-selection follicles as compared to that in the granulosa cells from other follicles. In contrast, the expression of Per2 mRNA was significantly increased in the granulosa cells from preovulatory follicles as compared to that in the granulosa cells from other follicles. Bmal1 and Cry mRNA expressions did not change across different follicular stages. FSH stimulated the expression of Clock mRNA in the cultured granulosa cells. The expression of Bmal1, Cry and Per2 mRNAs was not affected by FSH. Our results suggested that Clock may be associated with follicular development in the bovine ovary. In summary, our results suggested that circadian clock genes play an important role during follicular development in the bovine ovary.