The Role of cGMP in Oocyte Maturation of Zebrafish
Jianzhen Li*
College of Life Sciences, Northwest Normal University, Lanzhou, China
The role of cyclic guanosine monophosphate (cGMP) signal in the oocyte maturation attracted much attention in recent year, but its roles in fish reproduction is still largely unknown. Using zebrafish as a model, we have demonstrated for the first time in fish that cGMP is important in regulating oocyte maturation. In ovarian follicles, cGMP can be regulated by nitric oxide (NO) through soluble guanylate cyclase (sGC) to regulate oocyte maturation. Interestingly, using a variety of inhibitors and activators, we found that increase or decrease of the concentration of NO/sGC/cGMP in follicles could induce oocyte maturation through different signaling pathways. Furthermore, we found that the concentrations of NO and cGMP in follicular cells could be up-regulated by LH. During oocyte maturation, the concentration of cGMP in follicular cell layer were up-regulated, whereas the cGMP concentration in oocytes was down-regulated. These findings prompted us to propose a hypothesis on the role of cGMP in regulating oocyte maturation in zebrafish: LH signal stimulates NO and cGMP in follicular cells, thereby regulating some maturation promoting factors to induce oocyte maturation; meanwhile the cGMP in oocyte is decreased, then block the PDE3/cAMP to induce oocyte maturation. These findings would help us to understand the molecular mechanism of fish oocyte maturation.
Key Words: ovary; oocyte maturation; cGMP; nitric oxide; luteinizing hormone
Jianzhen Li*
College of Life Sciences, Northwest Normal University, Lanzhou, China
The role of cyclic guanosine monophosphate (cGMP) signal in the oocyte maturation attracted much attention in recent year, but its roles in fish reproduction is still largely unknown. Using zebrafish as a model, we have demonstrated for the first time in fish that cGMP is important in regulating oocyte maturation. In ovarian follicles, cGMP can be regulated by nitric oxide (NO) through soluble guanylate cyclase (sGC) to regulate oocyte maturation. Interestingly, using a variety of inhibitors and activators, we found that increase or decrease of the concentration of NO/sGC/cGMP in follicles could induce oocyte maturation through different signaling pathways. Furthermore, we found that the concentrations of NO and cGMP in follicular cells could be up-regulated by LH. During oocyte maturation, the concentration of cGMP in follicular cell layer were up-regulated, whereas the cGMP concentration in oocytes was down-regulated. These findings prompted us to propose a hypothesis on the role of cGMP in regulating oocyte maturation in zebrafish: LH signal stimulates NO and cGMP in follicular cells, thereby regulating some maturation promoting factors to induce oocyte maturation; meanwhile the cGMP in oocyte is decreased, then block the PDE3/cAMP to induce oocyte maturation. These findings would help us to understand the molecular mechanism of fish oocyte maturation.
Key Words: ovary; oocyte maturation; cGMP; nitric oxide; luteinizing hormone