Biological significance of sperm-independent calcium oscillations in immature oocytes of mice.

Sperm-independent Ca 2+ oscillations are induced in immature oocytes, and presumably contribute to oocyte quality; however, its physiological role remains unclear. We studied the significance of Ca 2+ oscillations in ovarian functions using extramitochondrial citrate synthase ( eCs )-deficient (KO) female mice. In wild-type mice, the percentage of Ca 2+ oscillation-induced oocytes gradually decreased during their juvenile period, and dropped at the beginning of their adult period, whereas its percentage reduced more slowly in juvenile eCs -KO mice. Moreover, ovarian follicles containing two oocytes were frequently observed in ovaries of adult eCs -KO female mice. We assume that eCS suppresses spontaneous Ca 2+ oscillations, probably maintaining ovarian functions.