Biogenesi Reproductive Medicine Centre, Istituti Clinici Zucchi, Via Zucchi, 24, Monza, Italy.
Mol Hum Reprod. 2014 Mar;20(3):200-7. doi: 10.1093/molehr/gat085. Epub 2013 Nov 20.
In mature mammalian oocytes, cortical f-actin distribution is polarized, as evidenced by a prominent cap subtended by the metaphase II (MII) spindle. Formation of a polarized actin cap is a consequence of a complex actomyosin-driven contractile process that directs polar body extrusion. Human mature oocytes also display a network of suboolemmal actin, but so far there has been no suggestion of an actin-rich domain in the vicinity of the spindle. By high-resolution confocal microscopy, we generated semi-quantitative data of the actin cytoskeleton in human mature and immature oocytes, with the aim to better understand the characteristics and remodelling of this cytoskeletal component in the female gamete. In mature MII oocytes, the cortical domain near the spindle showed a more intense actin signal in comparison to the opposite cortical domain (177.2±59.0 versus 126.8±61.0, P<0.0001; data expressed in arbitrary units). The extent of cortical f-actin polarity was comparable between in vivo and in vitro matured oocytes. However, both the degree of polarity and relative abundance of signal were diminished with increasing maternal age. Mean intensity of cytoplasmic actin was significantly higher in oocytes matured in vitro derived from in vitro maturation (IVM) cycle, in comparison to oocytes matured in vivo or in vitro obtained from controlled ovarian stimulation cycles (35.0±8.0, 21.1±12.4 and 25.9±8.6, respectively; P=0.025). In germinal vesicle (GV)-stage oocytes obtained from both IVM and controlled ovarian stimulation cycles, cortical actin did not appear polarized, irrespective of whether the GV was located centrally or asymmetrically. These data indicate that, during maturation, cortical actin acquires a polarized distribution involving an accumulation in the domain adjacent the spindle. They also propose new questions concerning the existence of cytoplasmic actin in mature oocytes. Finally, they are suggestive of an influence of maternal age on the actin cytoskeleton.
在成熟的哺乳动物卵母细胞中，皮质 F-肌动蛋白的分布是极化的，这可以从由中期 II（MII）纺锤体支撑的明显帽状结构得到证明。极化肌动蛋白帽的形成是一个复杂的肌动球蛋白驱动的收缩过程的结果，该过程指导极体挤出。人类成熟卵母细胞也显示出亚膜下肌动蛋白网络，但到目前为止，还没有关于纺锤体附近存在富含肌动蛋白的区域的建议。通过高分辨率共聚焦显微镜，我们生成了人类成熟和不成熟卵母细胞中肌动蛋白细胞骨架的半定量数据，旨在更好地了解雌性配子中这种细胞骨架成分的特征和重塑。在成熟的 MII 卵母细胞中，与纺锤体相对的皮质区域显示出比相反皮质区域更强的肌动蛋白信号（177.2±59.0 与 126.8±61.0，P<0.0001；数据以任意单位表示）。体内成熟和体外成熟卵母细胞的皮质 F-肌动蛋白极性程度相当。然而，随着母体年龄的增加，极性程度和相对信号丰度都降低了。与体内成熟或从控制性卵巢刺激周期获得的体外成熟卵母细胞相比，来自体外成熟（IVM）周期的成熟卵母细胞中的细胞质肌动蛋白的平均强度明显更高（分别为 35.0±8.0、21.1±12.4 和 25.9±8.6；P=0.025）。来自 IVM 和控制性卵巢刺激周期的GV 期卵母细胞中，皮质肌动蛋白似乎没有极化，无论 GV 是位于中央还是不对称位置。这些数据表明，在成熟过程中，皮质肌动蛋白获得了一种涉及纺锤体相邻区域积累的极化分布。它们还提出了有关成熟卵母细胞中细胞质肌动蛋白存在的新问题。最后，它们表明母体年龄对肌动蛋白细胞骨架有影响。
