The mean age of first-time mothers is on the rise, with serious consequences for maternal health and that of their offspring. Older maternal age is strongly associated with birth defects, miscarriage, and infertility. These poor reproductive outcomes can frequently be traced back to defects in follicular and oocyte quantity and quality that occur with ovarian aging. A continuous decline in the quantity of ovarian follicles (i.e. the ?ovarian reserve?) occurs during reproductive aging, as the pool of primordial follicles is continuously depleted. Additionally, oocyte quality declines as follicles and oocytes accumulate DNA damage over time, a process which accelerates even more rapidly when the ovary is exposed to gonadotoxins. There is therefore an urgent need to better understand the mechanisms that control follicular and oocyte quantity and quality in order to support the health of women and their children. The noncoding RNAs H19 and let-7 play essential roles in mammalian development, but little is known about their role in ovarian follicle growth and oocyte function. We have uncovered a plausible mechanism for noncoding-RNA-based regulation of follicular health via the H19/let-7 pair. We previously showed that H19 binds and antagonizes the miRNA let-7. We also demonstrated that in the absence of H19, ovarian AMH expression is decreased, follicular recruitment is accelerated, and fertility is compromised. We have observed that AMH has a functional let-7 binding site, suggesting a ncRNA-mediated mechanism for AMH regulation by H19 via let-7. Moreover, our preliminary data suggests altered response to DNA damage in the absence of H19. Thus, there is plausible mechanistic insight into, and strong support for, the role of H19 and let- 7 in the regulation of follicular/oocyte recruitment and function.
In Aim 1, we will determine the role of H19 in E2- and AMH-mediated regulation of follicle quantity.
In Aim 2, we will determine whether ovaries of H19KO mice are more susceptible to DNA damage than their WT counterparts. Lastly, for Aim 3, we will determine whether the abnormal follicular development and expression of DNA damage genes observed in H19KO mice is mediated via let-7 and identify changes in the transcriptome of somatic cells and oocytes related to loss of H19. Our approach is innovative because it represents a substantive departure from the status quo by defining noncoding RNAs (ncRNAs) as major regulators of oocyte quantity and quality, and has the potential to lead to novel, ncRNA-based treatments for a broad range of reproductive disease states.
Reproductive health issues as serious as miscarriage, birth defects, and the loss of fertility due to advancing age or exposure to gonadotoxic agents can frequently be traced back to a decline in oocyte quality and/or quantity. We have discovered that the noncoding RNAs H19 and let-7 regulate genes involved in follicular recruitment and DNA repair, processes whose regulation is essential for the maintenance and growth of an adequate population of healthy oocytes. Our proposed studies have the potential to define noncoding RNAs as major regulators of ovarian reserve, and are directly related to the NIH Fertility and Infertility Branch?s mission of supporting research that enhances our understanding of normal reproduction and reproductive pathophysiology.