Peculiarities of the Mammalian Oocyte Cell Cycle

Oocyte meiosis, the process of egg cell formation, requires a highly regulated cell cycle with many unique features compared to somatic cell division. On the journey to create a healthy embryo, this special cell carries a heavy responsibility and must navigate a remarkable number of complex challenges. Most oocytes will never complete this journey; less than 0.1% are ever ovulated, and fewer are viable. However, the few that do complete it manage by the execution of a series of extraordinary adaptations through two rounds of cell division. In this review, we discuss some of these challenges and the adaptations that have evolved to mitigate them. This is not intended to be a comprehensive review of the cell cycle in oocyte meiosis but to highlight some of the differences between oocyte meiosis and a typical mitosis. We discuss features that make this cell unique and the cell cycle regulatory mechanisms that support them. We salute the few that make it and those that are sacrificed along the way.