Lefèvre B, Nagyova E, Pesty A, Testart J
AVCR (Czech Academy of Sciences), Libèchov, Czech Republic.
Exp Cell Res. 1997 Oct 10;236(1):193-200. doi: 10.1006/excr.1997.3720.
The meiosis resumption process has been related to spontaneous cytoplasmic InsP3-dependent calcium oscillations in fully grown mouse oocytes. Our purpose was to determine whether the acquisition of meiotic competence during the growth phase of oogenesis was associated with that of Ca2+ oscillations and whether these oscillations were dependent on the phosphoinositide cycle. We used confocal laser scanning microscopy to image free calcium ions in fluo-3/AM-loaded oocytes recovered from 12- to 26-day-old mice for 15 min following follicular release. As expected, oocytes isolated from 12-day-old mice were totally incompetent to undergo GVB in vitro, whereas the GVB rate increased progressively with mouse age and oocyte diameter. The percentage of oocytes exhibiting spontaneous calcium oscillations and that of oocytes resuming meiosis were similarly correlated with the female age, with incompetent oocytes failing to exhibit spontaneous Ca2+ oscillations. It is noteworthy that regardless of the stage of growth, thapsigargin induced an ooplasmic calcium release from the InsP3-sensitive stores when it was added to the culture medium. However, intracytoplasmic microinjection of InsP3 induced a shorter sequence of Ca2+ oscillations in 12-day-old mouse oocytes than in 15-day-old mouse oocytes and, whereas InsP3 increased the GVB rate at 15 days, it was unable to induce GVB at 12 days. These data lead us to conclude that the acquisition of meiotic competence is related to the functionality of the InsP3 pathway and, correspondingly, to the oocyte's ability to generate spontaneous cytoplasmic InsP3-dependent calcium oscillations.
减数分裂恢复过程与完全成熟的小鼠卵母细胞中自发的、依赖肌醇三磷酸（InsP3）的细胞质钙振荡有关。我们的目的是确定在卵子发生的生长阶段减数分裂能力的获得是否与钙离子振荡的获得相关，以及这些振荡是否依赖于磷酸肌醇循环。我们使用共聚焦激光扫描显微镜对从12至26日龄小鼠中回收的、用fluo-3/AM加载的卵母细胞中的游离钙离子进行成像，在卵泡释放后持续15分钟。正如预期的那样，从12日龄小鼠中分离出的卵母细胞在体外完全没有能力进行生发泡破裂（GVB），而GVB率随着小鼠年龄和卵母细胞直径的增加而逐渐升高。表现出自发钙振荡的卵母细胞百分比和恢复减数分裂的卵母细胞百分比与雌性年龄同样相关，没有能力的卵母细胞不会表现出自发的Ca2+振荡。值得注意的是，无论生长阶段如何，当毒胡萝卜素添加到培养基中时，它都会诱导从InsP3敏感储存库中释放卵质钙。然而，与15日龄小鼠卵母细胞相比，向12日龄小鼠卵母细胞中进行胞质内显微注射InsP3会诱导更短序列的Ca2+振荡，并且，虽然InsP3在15天时增加了GVB率，但在12天时它无法诱导GVB。这些数据使我们得出结论，减数分裂能力的获得与InsP3途径的功能相关，相应地，也与卵母细胞产生自发的、依赖细胞质InsP3的钙振荡的能力相关。
