Regulation of Oocyte Viability by Granulosa Cell Contact

描述(申请人提供)：一旦原始卵泡的数量耗尽，就会发生更年期。此外，原始卵泡的迅速枯竭与年龄相关的生育力下降和卵巢早衰有关。据估计，大约70%的卵泡因卵母细胞死亡而丢失。除此之外，人们对这些小卵泡的维持机制知之甚少。深入了解影响原始卵泡的生存机制可能来自于了解这些卵泡是如何形成的。 在胚胎发育过程中，原始生殖细胞迁移到发育中的哺乳动物卵巢，增殖并进入减数分裂前期。在这个阶段，许多PGC通过一种称为细胞凋亡的特殊途径死亡。然而，一些原生殖细胞与体细胞(假定为颗粒细胞)建立联系以形成原始卵泡。这些PGC，现在被称为卵母细胞，似乎受到保护，不会发生凋亡。这一过程发生在包括人类在内的所有哺乳动物物种中。虽然几十年来人们一直知道细胞接触似乎可以保护卵母细胞免于死亡，但细胞接触促进卵母细胞存活的机制却完全不清楚。 已知颗粒细胞与卵母细胞的相互作用在一定程度上是由黏附蛋白E-和N-钙粘蛋白介导的。根据我们以前对颗粒细胞凋亡的研究，我们认为E和/或N-钙粘素介导的细胞接触刺激卵母细胞内的磷脂酰肌醇3激酶(PI3K)活性。进一步提出，PI3K最终起到维持卵母细胞活力的作用。 了解颗粒细胞如何与卵母细胞相互作用以保持卵母细胞的活力，可以为不孕不育的各个方面以及控制进入更年期的机制提供重要的见解。因此，我们将确定：1)颗粒细胞接触对卵母细胞体外凋亡率的影响；2)E和/或N-钙粘素介导的细胞接触是否调节卵母细胞的存活率；3)E和/或N-钙粘素介导的细胞接触是否刺激PI3K活性，从而维持卵母细胞的存活率。

DESCRIPTION (provided by applicant): Menopause occurs once the number of primordial follicles is depleted. Moreover, a rapid depletion of primordial follicles is associated with the age-related decline in fertility and premature ovarian failure. It has been estimated that about 70% of these follicles are lost because of oocyte death. Other than this, extremely little is known about the mechanism by which these small follicles are maintained. Insight into the survival mechanisms that influence primordial follicles could come from understanding how these follicles are formed. During embryonic development, primordial germ cells (PGCs) migrate into the developing mammalian ovary, proliferate and then enter meiotic prophase. At this stage, many of the PGCs die via a specific pathway known as apoptosis. However, some PGCs establish contact with somatic cells (presumptive granulosa cells) to form primordial follicles. These PGCs, now referred to as oocytes, appear to be protected from undergoing apoptosis. This process occurs in all mammalian species including humans. While it has been known for decades that cell contact seems to protect oocytes from dying, the mechanism through which cell contact promotes oocyte survival is completely unknown. It is known that granulosa cell-oocyte interaction is mediated, in part, by the adhesion proteins, E- and N-cadherin. Based on our previous studies of granulosa cell apoptosis, we propose that E- and/or N-cadherin mediated cell contact stimulates phosphatidylinositol 3 kinase (PI3K) activity within the oocyte. It is further proposed that PI3K ultimately acts to maintain the viability of the oocyte. Understanding how granulosa cells interact with oocytes to preserve oocyte viability could provide important insights into various aspects of infertility and the mechanisms that control entry into menopause. Therefore, we will determine: 1) the effect of granulosa cell contact on the rate at which oocytes undergo apoptosis in vitro; 2) whether E- and/or N-cadherin mediated cell contact regulates oocyte viability; and 3) whether E- and/or N-cadherin mediated cell contact stimulates PI3K activity and thereby maintains oocyte viability.