Fertilization-induced maturation of cortical ER clusters in oocytes; impact of maternal age

项目摘要/摘要 皮质内质网结构是卵母细胞质量的一个关键方面，在哺乳动物中就是一个例子，那里有独特的内质网簇。 放置在靠近质膜(PM)的位置。我们最近的活体研究表明 皮质肌动蛋白层中存在迄今未知的肌动蛋白窗，此外，内质网簇是 位于这些窗孔的中央，精子结合优先于这些窗孔。 另一个新的观察是，在精子融合时，卵母细胞内质网簇经历了成熟事件 涉及到体积的增加，停靠在肌动蛋白层的栅栏上。这让我们得出了一个假设，即首相 覆盖在ER簇上的精子结合蛋白丰富，促进精子之间的密切相互作用， 卵母细胞PM和内质网簇。时间和机制研究是必要的，以阐明 卵母细胞皮质肌动蛋白窗孔在建立精子结合部位以及精子中的作用 精子头释放ζ介导内质网簇成熟变化。.的存在 独特的肌动蛋白Fenestrae导致了第二个假说，即肌动蛋白重塑蛋白RhoA和cdc42可以 调节精子结合部位，通过肌动蛋白窗孔形成皮质内质网簇。最后，我们观察到， 老年雌性小鼠的卵母细胞表现出异常的内质网结构，其形成能力也有很大差异 ER簇对受精的响应。这一发现导致我们提出了第三个假说，即母体衰老 扰乱肌动蛋白窗孔和钙离子振荡，导致内质网簇成熟缺陷和生育力下降。 我们的发现提出了一种新的范式，即卵母细胞通过内质网簇对精子结合/融合做出反应 成熟，然后在精子进入卵子的过程中与精子建立密切的相互作用。测试 这项提案中提出的假设将使人们对受精过程有更深入的了解， 以及改进辅助生殖技术的潜在机制，如ICSI和 生殖老化的卵母细胞以及潜在的阻止受精的新避孕目标。

PROJECT SUMMARY/ABSTRACT Cortical ER structure is a key aspect of oocyte quality as exemplified in mammals where unique `ER clusters' become positioned in close proximity to the plasma membrane (PM). Our recent in vivo studies demonstrate the presence of hereto unknown actin fenestrae within cortical actin layer, in addition the ER clusters were centrally located within these fenestrae and sperm binding occurred preferentially over these fenestrae. Another novel observation was that upon sperm fusion the oocyte ER clusters undergo a maturational event involving an increase in volume, docking to fenestrae in the actin layer. This led us to a hypothesis that the PM overlying ER clusters is enriched in sperm binding proteins that promote close interaction between the sperm, oocyte PM, and the ER cluster. Temporal and mechanistic studies are necessary to elucidate the role of the oocyte cortical actin fenestrae in the establishment of sperm binding sites as well as the role of the sperm PLCζ released from the sperm head in mediating the ER cluster maturational changes. The presence of unique actin fenestrae led to a second hypothesis that actin remodeling proteins, RhoA and cdc42, could modulate sperm binding sites, cortical ER cluster formation via the actin fenestrae. Lastly, we observed that oocytes from aged female mice exhibited abnormal ER structure and varied considerably in their ability to form ER clusters in response to fertilization. This finding led us to propose a third hypothesis where maternal aging disrupts actin fenestrae and Ca2+ oscillations, causing defects in ER cluster maturation and reduced fertility. Our findings suggest a new paradigm wherein the oocyte responds to sperm binding/fusion by ER cluster maturation, then establishes close interaction with the sperm during its incorporation into the egg. Testing of the hypotheses presented in this proposal will lead to an enhanced understanding of the fertilization process, and potential mechanisms for improving Assisted Reproduction Technologies such as ICSI and protocols for reproductively aged oocytes as well as potential new contraceptive targets that block fertilization.