In mammals, the mature ovulated egg is arrested in metaphase II of the first meiotic division. The signal that triggers the transition from meiosis to mitosis is provided by the fertilising sperm and takes the form of a series of Ca 2+ oscillations. The pattern of Ca 2+ oscillations is imposed by maternal control mechanisms that ensure Ca 2+ transients occur during M-phase of meiosis II and during the first mitotic division. The transition from meiosis to mitosis involves a major re-organisation. The unfertilised egg is polarised with the meiotic spindle located in the cortex of the animal pole and clusters of endoplasmic reticulum in the vegetal hemisphere. By the time of the first mitotic division some 20 h later the spindle has formed in the centre of the embryo and is surrounded by endoplasmic reticulum. These changes in organisation have implications for the inheritance of ER in meiotic and mitotic cell divisions and may reflect different roles and requirements for Ca 2+ in meiosis and mitosis.
|Journal||European Journal of Obstetrics & Gynecology and Reproductive Biology|
|Publication status||Published - 1 Jul 2004|
|Event||Genesis and Fate of the Preimplantation Embryo - Sorreno, Italy|
Duration: 29 Sep 2003 → 1 Oct 2003