卵母细胞与次黄嘌呤协同调控猪卵泡颗粒细胞G2/M期转变的分子机制

卵泡发育过程中，卵母细胞被抑制在双线期，而卵泡颗粒细胞却能够活跃增殖。卵泡液中的次黄嘌呤（Hx）通过抑制磷酸二酯酶的活性提高cAMP水平，从而抑制卵母细胞促成熟因子（MPF）活性维持卵母细胞减数分裂抑制。颗粒细胞的增殖同样需要MPF活性，次黄嘌呤对颗粒细胞增殖的影响却未见报道。项目前期研究证实，生理浓度的Hx能够通过抑制MPF活性，将颗粒细胞阻断在G2期，并且这种抑制作用的解除依赖于TGF-β1的添加，而不是FSH、LH、IGF1、EGF等激素或生长因子。GDF9和BMP15是卵母细胞分泌促进颗粒细胞增殖的TGF-β超家族成员，卵母细胞是否通过分泌GDF9和BMP15解除Hx对颗粒细胞有丝分裂的抑制以及是否通过ERK-Cdc25B/Wee1/Myt1-CDK1-MPF信号通路发挥作用是本项目关键科学问题。项目研究结果对于深入了解卵泡发育机制以及发展促进卵泡发育的技术方法都具有重要意义。

During follicular development, oocyte is inhibited in the diplotene stage, while granulosa cells in the same environment can actively proliferate. Hypoxanthine (Hx) in follicular fluid increases the level of cAMP by inhibiting the activity of phosphodiesterase, thus inhibiting the activity of oocyte maturation promoting factor (MPF) to maintain the meiosis inhibition of oocyte. The proliferation of granulosa cells also requires MPF activity. The effect of hypoxanthine in follicular fluid on the proliferation of granulosa cells has not been reported. Previous studies have confirmed that Hx at physiological concentration can block the cell cycle of granulosa cells in G2 phase by inhibiting MPF activity, and the elimination of this inhibition depends on the addition of TGF-beta 1, rather than hormones or growth factors, such as FSH, LH, IGF1, EGF. GDF9 and BMP15 are members of the TGF-beta superfamily that oocyte secretes and promotes granulosa cell proliferation. Whether oocyte secretes GDF9 and BMP15 to relieve the inhibition of Hx on granulosa cell mitosis and whether they play a role through ERK-Cdc25B/Wee1/Myt1-CDK1-MPF signaling pathway is the key scientific issue and research focus of this project. The results of the project will be of great significance for further understanding the mechanism of follicular development and developing the technical methods to promote follicular development.