Ovaries of females of domestic mammals contain abundant population of growing oocytes. These oocytes did not develop meiotic competence or its meiotic competence is only partially acquired. These oocytes cannot be used in reproductive biotechnologies dueto their low developmental competence. Processes involved in the acquisition of meiotic competence are not fully understood. This project will test hypothesis that the acquisition of meiotic competence is at least partially regulated by protein phosphatase calcineurin. We will anylze mRNA for calcineurin A or calcineurin B in pig oocytes at different levels of meiotic competence. Expression of calcineurin proteins will be detected in growing pig oocytes and localization of these proteins will be detected. The role of calcineurin will be also investigated using oocyte culture with specific calcineurin inhibitors.