A major goal of my research program is to identify molecules and metabolic pathways that participate in the control of oocyte maturation in mammals. It is well established that meioticallly competent mammalian oocytes are held in prophase I arrest by inhibitory levels of cAMP and that a fall in oocyte cAMP levels is required for meiotic resumption. In the mouse, the oocyte-specific phosphodiesterase PDE3 has been shown to be essential for meiotic resumption. It is generally thought that PDE3-mediated meiotic resumption is due to removal of cAMP and thus release of the inhibitory action of cAMP-dependent protein kinase on the oocyte. However, PDE3 cleavage of cAMP produces 5-AMP, which is a potent activator of the stress response enzyme, AMP-activated protein kinase (AMPK). In recent studies, we have established the presence of AMPK in mouse oocytes and have shown that it mediates meiotic resumption in mouse oocytes under a variety of stimuli, including hormones, modulation of AMP levels, and stress. While we have established a role for AMPK in germinal vesicle breakdown (GVB), little is known about its role throughout the maturation period.
In Specific Aim 1, we will determine the influence of AMPK from prophase I to Metaphase II and the association of the kinase with chromosomes and microtubules. We will also test the idea that, by promoting meiotic progression past metaphase I, AMPK prevents premature activation. Additional comparative experiments with rat oocytes will determine if, like in mouse oocytes, AMPK plays a role in meiotic maturation.
In Specific Aim 2, we will use an antisense morpholino approach to knock down AMPK catalytic subunit in mouse oocytes to determine whether meiotic induction in mice is absolutely dependent on AMPK. These results will help delineate specific metabolic pathways involved in meiotic maturation and will have important implications for both fertility and contraception. In addition, AMPK is an important component of overall body metabolism, and its regulation is a target for drug therapies aimed at alleviating type II diabetes and metabolic syndrome. Understanding its impact on reproduction may help in minimizing unwanted side effects in future therapies.
The experiments in this application will help advance our understanding of meiotic regulation in mammalian oocytes and will have important implications for both fertility and contraception. In addition, the enzyme under investigation, AMPK, is a crucial component in mechanisms controlling energy homeostasis and is a target for drug therapies aimed at alleviating type II diabetes and metabolic syndrome. Since the incidence of these conditions in the general population is increasing at alarming rates, understanding the impact of AMPK regulation on reproduction will provide important information that will help minimize unwanted side effects in future therapies.
