MicroRNA Regulation of Ovarian Function

描述(申请人提供)：避孕和不孕不育是育龄妇女面临的两个主要生活质量问题。可受精卵母细胞的排卵和功能性黄体的形成是生殖成功的绝对要求，是由黄体生成素(LH)周期中期激增引起的。黄体生成素分泌紊乱是导致不孕的主要原因，也是许多避孕方法的目标。大量的研究已经表征了黄体生成素作用下游的信号级联和转录反应；我们对黄体生成素及其受体如何能够调节排卵、恢复减数分裂和黄体化等复杂的生理过程的理解也取得了巨大的进展。然而，重要的问题仍然没有得到解决或探索，包括转录后基因表达调控在调节促黄体生成素作用中所起的作用。我们最近对Dicer1缺陷小鼠的研究表明，转录后调控，特别是microRNA介导的基因调控在排卵中起着关键作用。我们还发现miR-21是一种位于排卵周卵泡颗粒细胞内的由黄体生成素诱导的微小RNA(MiRNA)，并证明它通过促进整体翻译来抑制细胞凋亡和促进颗粒细胞肥大。此外，我们目前的体内研究表明，miR-21的缺失会降低排卵率。因此，这一建议的中心假设是miR-21在促黄体生成素诱导的卵巢功能中起关键作用。为了验证这一中心假设，在特定的Aim1中，我们确定了miR-21在排卵周卵泡颗粒细胞中的功能及其在排卵、黄体化和卵母细胞功能中的作用。在特定目标2中，我们确定了miR-21在排卵周颗粒细胞中调控的靶转录本和分子途径，而在特定目标3中，我们确定了哪些黄体生成素诱导的转录因子调节miR-21基因的表达。这项拨款申请中提出的研究将定义由miR-21介导的转录后基因调控的基因子集，并将从功能上将这种miRNA与对卵巢功能至关重要的生理和发育事件联系起来。这项研究的长期益处将增强我们对卵巢的了解，最终影响不孕不育治疗策略的发展和妇女新的避孕方法。

DESCRIPTION (provided by applicant): Contraception and infertility are two major quality of life issues facing women of reproductive age. Ovulation of a fertilizable oocyte and formation of a functional corpus luteum are absolute requirements for reproductive success and are induced by the mid-cycle surge of luteinizing hormone (LH). Disrupted LH actions are a leading cause of infertility and a target of many contraceptive methods. Numerous studies have characterized the signaling cascades and transcriptional responses downstream of LH action; and dramatic progress in our understanding of how LH and its receptor are able to regulate such complicated physiological processes such as ovulation, resumption of meiosis and luteinization have resulted. However, significant questions still remain unsolved or unexplored, including the role post-transcriptional regulation of gene expression plays in mediating LH action. Our recent studies with Dicer1 deficient mice have implicated post-transcriptional and specifically microRNA mediated gene regulation as playing a key role in ovulation. We have also identified miR-21 as an LH- induced microRNA (miRNA) within granulosa cells of the periovulatory follicle, and demonstrated that it suppresses apoptosis and enhances granulosa cell hypertrophy by promoting global translation. Furthermore, our current in vivo studies demonstrate that loss of miR-21 decreases ovulation rate. Therefore, the central hypothesis of this proposal is that miR-21 plays critical roles in the LH-induced ovarian function. To test this central hypothesis, in Specific Aim1, we determine the function of miR-21 within periovulatory follicular granulosa cells and its role in ovulation, luteinization and oocyte competence. In Specific Aim 2, we identify the target transcripts and molecular pathways miR-21 regulates within periovulatory granulosa cells, while in Specific Aim 3 we determine which LH-induced transcription factors modulate miR-21 gene expression. The studies proposed in this grant application will define a subset of genes regulated by miR-21 mediated post-transcriptional gene regulation and will functionally link this miRNA with physiologic and developmental events critical to ovarian function. The long-term benefits of this research will enhance our understanding of the ovary, ultimately impacting the development of treatment strategies for infertility and new contraceptive methods for women.