|
Oocyte (or ovum/egg) activation is a series of processes that occur in the oocyte during fertilization. Sperm entry causes calcium release into the oocyte. In mammals, this has been proposed to be caused by the introduction of phospholipase C isoform zeta (PLCζ) from the sperm cytoplasm, although this remains to be established definitively. Activation of the ovum includes the following events: * Cortical reaction to block against other sperm cells * Activation of egg metabolism * Reactivation of meiosis * DNA synthesis ==Sperm trigger of egg activation== The sperm may trigger egg activation via the interaction between a sperm protein and an egg surface receptor. Izumo is the sperm cell signal, that will trigger the egg receptor Juno. This receptor is activated by the sperm binding and a possible signalling pathway could be the activation of a tyrosine kinase which then activates phospholipase C (PLC). The inositol signaling system has been implicated as the pathway involved with egg activation. IP3 and DAG are produced from the cleavage of PIP2 by phospholipase C. However, another hypothesis is that a soluble 'sperm factor' diffuses from the sperm into the egg cytosol upon sperm-oocyte fusion. The results of this interaction could activate a signal transduction pathway that uses second messengers. A novel PLC isoform, PLCζ, may be the equivalent of the mammalian sperm factor. A 2002 study demonstrated that mammaliam sperm contain PLC zeta which can start the signaling cascade. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Oocyte activation」の詳細全文を読む スポンサード リンク
|