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MI arrest and MI pause in starfish oocytes

海星卵母细胞中的 MI 停滞和 MI 暂停

基本信息

批准号：
17370079
负责人：
CHIBA Kazuyoshi
金额：
$ 8.64万
依托单位：
Ochanomizu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17370079/
关键词：
MAPK Na+H+ exchanger starfish oocytes MI pause phosphorylation intracellular pH meiosis MI arrest H^+エクスチェンジャー p90RS 細胞・組織生体分子動物発生・分化

项目摘要

In many animals, oocytes arrest at metaphase of the first or second meiotic division (MI or MII) prior to fertilization. Meiosis reinitiation occurs after fertilization. Starfish oocytes were usually isolated from the ovary without stimulation, placed in seawater, and then treated with 1-MA in most studies. In this in vitro oocyte maturation, meiotic division of maturing oocytes proceeds without arrest, followed by formation of two polar bodies. However, when 1-MA is injected into the body cavity of the animal to induce in vivo oocyte maturation, GVBD occurs but polar bodies are not formed in the ovary, indicating that ovarian oocytes arrest at MI.In this study using starfish Asterina pectinifera, the duration of MI after spawning was~20 min and~30 min in fertilized and unfertilized oocytes, respectively. This prolongation of MI in unfertilized oocytes, referred to as the MI pause, was maintained by MAPK as well as low intracellular pH (~7.0). MI pause was released by intracellulat pH increase by Na^+/H^+ exchanger. MI arrest was not maintained by MAPK, since it was inactive in the oocytes arrested at MI in the ovary and activated immediately after spawning. Also cyclin B was not degraded at pH 6.7 in the cell-free preparation without MAPK activity, while it was degraded at pH 7.0, suggesting that MI arrest was solely maintained by lower pH (<7.0). Normal development occurred when the spawned oocytes were fertilized before the first polar body formation, while fertilization after the first polar body formation increased the rate of abnormal development. Thus, due to MI pause and MI arrest, the probability to be fertilized before the polar body formation could be increased, leading to normal development.

在许多动物中，卵母细胞在受精前的第一次或第二次减数分裂（MI或MII）中期停滞。减数分裂在受精后重新开始。大多数研究通常将海星卵母细胞从卵巢中分离出来，不进行刺激，置于海水中，然后用1-MA处理。在这种体外卵母细胞成熟过程中，成熟卵母细胞的减数分裂不受阻碍地进行，随后形成两个极体。然而，当将1-MA注入动物体腔诱导卵母细胞在体内成熟时，卵巢内发生GVBD，但未形成极体，表明卵巢卵母细胞在MI处停滞。本研究以海星Asterina pectinifera为研究对象，受精和未受精卵母细胞产卵后MI持续时间分别为~20 min和~30 min。在未受精的卵母细胞中，这种心肌梗死的延长被称为心肌梗死暂停，由MAPK和低细胞内pH值（~7.0）维持。Na^+/H^+交换剂使细胞内pH升高，从而释放心肌梗死暂停。由于MAPK在卵巢中被MI捕获的卵母细胞中不活跃，并在产卵后立即激活，因此MAPK不能维持MI捕获。此外，在无MAPK活性的无细胞制备中，细胞周期蛋白B在pH为6.7时未被降解，而在pH为7.0时被降解，这表明仅通过较低的pH（<7.0）才能维持心肌梗死的停止。在第一极体形成前受精卵发育正常，而在第一极体形成后受精卵发育异常的几率增加。因此，由于MI暂停和MI停止，可以增加极体形成前受精的可能性，从而导致正常发育。