Mechanisms of Xenopus oocyte maturation

Abstract

Publisher Summary This chapter discusses the mechanisms of xenopus oocyte maturation. Although many aspects of the meiotic cell cycle are similar to the mitotic cell cycle, the differences between them are critical for the accurate reduction of genetic material. The immature stage VI oocytes of Xenopus are arrested in prophase of meiosis I; this arrest can last several months until maturation is initiated with the hormone progesterone. Meiotic maturation consists of entry into and completion of meiosis I, entry into meiosis II, and arrest at metaphase of meiosis II. The metaphase arrest is maintained until fertilization, which releases the arrest and initiates the series of rapid embryonic cell cycles. The meiotic cell cycle consists of two consecutive M phases without an intervening S phase. The first meiotic division is the reductive division: The two pairs of sister chromatids align at M phase and the bivalent pairs separate at anaphase I. The sister chromatids do not separate at this division. The second meiotic division is similar to mitosis: One pair of sister chromatids aligns at M phase and anaphase II results in the separation of individual chromatids.