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Abstract：
UNASSIGNED: Much of the scientific knowledge on oocyte maturation, fertilization, and embryonic development has come from the experiments using gametes of marine organisms that reproduce by external fertilization. In particular, echinoderm eggs have enabled the study of structural and biochemical changes related to meiotic maturation and fertilization owing to the abundant availability of large and transparent oocytes and eggs. Thus, in vitro studies of oocyte maturation and sperm-induced egg activation in starfish are carried out under experimental conditions that resemble those occurring in nature. During the maturation process, immature oocytes of starfish are released from the prophase of the first meiotic division, and acquire the competence to be fertilized through a highly programmed sequence of morphological and physiological changes at the oocyte surface. In addition, the changes in the cortical and nuclear regions are essential for normal and monospermic fertilization. This review summarizes the current state of research on the cortical actin cytoskeleton in mediating structural and physiological changes during oocyte maturation and sperm and egg activation in starfish and sea urchin. The common denominator in these studies with echinoderms is that exquisite rearrangements of the egg cortical actin filaments play pivotal roles in gamete interactions, Ca2+ signaling, exocytosis of cortical granules, and control of monospermic fertilization. In this review, we also compare findings from studies using invertebrate eggs with what is known about the contributions made by the actin cytoskeleton in mammalian eggs. Since the cortical actin cytoskeleton affects microvillar morphology, movement, and positioning of organelles and vesicles, and the topography of the egg surface, these changes have impacts on the fertilization process, as has been suggested by recent morphological studies on starfish oocytes and eggs using scanning electron microscopy. Drawing the parallelism between vitelline layer of echinoderm eggs and the zona pellucida of mammalian eggs, we also discuss the importance of the egg surface in mediating monospermic fertilization.
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摘要：
■许多关于卵母细胞成熟的科学知识，受精,胚胎发育来自使用通过外部受精繁殖的海洋生物配子的实验。特别是,由于大量透明的卵母细胞和卵，棘皮动物卵能够研究与减数分裂成熟和受精有关的结构和生化变化。因此，在与自然界相似的实验条件下，对海星中卵母细胞成熟和精子诱导的卵激活进行了体外研究。在成熟过程中,海星的未成熟卵母细胞从第一次减数分裂的前期释放，并通过卵母细胞表面高度程序化的形态和生理变化序列获得受精的能力。此外,皮质和核区的变化对正常和单精子受精至关重要。本文综述了皮质肌动蛋白细胞骨架在介导海星和海胆卵母细胞成熟和精子和卵激活过程中的结构和生理变化的研究现状。与棘皮动物的这些研究的共同点是，卵皮质肌动蛋白丝的精致重排在配子相互作用中起关键作用，Ca2+信号，皮质颗粒的胞吐作用，和控制单精子受精。在这次审查中,我们还将使用无脊椎动物卵的研究结果与哺乳动物卵中肌动蛋白细胞骨架的作用进行了比较。由于皮质肌动蛋白细胞骨架影响微绒毛形态，运动,细胞器和囊泡的定位，和鸡蛋表面的地形，这些变化对施肥过程有影响，正如最近使用扫描电子显微镜对海星卵母细胞和卵进行的形态学研究所表明的那样。绘制棘皮动物卵的卵黄层与哺乳动物卵的透明带之间的平行度，我们还讨论了卵子表面在介导单精子受精中的重要性。
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