Dragovic Rebecca A, Ritter Lesley J, Schulz Samantha J, Amato Fred, Thompson Jeremy G, Armstrong David T, Gilchrist Robert B
Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, Medical School, University of Adelaide, Adelaide, South Australia 5005, Australia.
Biol Reprod. 2007 May;76(5):848-57. doi: 10.1095/biolreprod.106.057471. Epub 2006 Dec 27.
Expansion of the mouse cumulus-oocyte complex (COC) is dependent on oocyte-secreted paracrine factors. Transforming growth factor beta (TGFB) superfamily molecules are prime candidates for the cumulus expansion-enabling factors (CEEFs), and we have recently determined that growth differentiation factor 9 (GDF9) alone is not the CEEF. The aim of this study was to examine oocyte paracrine factors and their signaling pathways that regulate mouse cumulus expansion. Using RT-PCR, oocytes were found to express the two activin subunits, Inhba and Inhbb, and activin A and activin B both enabled FSH-induced cumulus expansion of oocytectomized (OOX) complexes. Follistatin, an activin-binding protein, neutralized activin-induced expansion but had no effect on oocyte-induced expansion. The type I receptors for GDF9 and activin are activin receptor-like kinase 5 (ALK5) and ALK4, respectively, both of which activate the same SMAD 2/3 signaling pathway. We examined the requirement for this signaling system using an ALK 4/5/7 inhibitor, SB-431542. SB-431542 completely ablated FSH-stimulated GDF9-, activin A-, activin B-, and oocyte-induced cumulus expansion. Moreover, SB-431542 also antagonized epidermal growth factor-stimulated, oocyte-induced cumulus expansion. Using real-time RT-PCR, SB-431542 also attenuated GDF9-, activin A-, and oocyte-induced OOX expression of hyaluronan synthase 2, tumor necrosis factor alpha-induced protein 6, prostaglandin synthase 2, and pentraxin 3. This study provides evidence that the CEEF is composed of TGFB superfamily molecules that signal through SMAD 2/3 to enable the initiation of mouse cumulus expansion.
小鼠卵丘-卵母细胞复合体（COC）的扩展依赖于卵母细胞分泌的旁分泌因子。转化生长因子β（TGFB）超家族分子是促使卵丘扩展因子（CEEFs）的主要候选分子，并且我们最近确定单独的生长分化因子9（GDF9）并非CEEF。本研究的目的是检测调节小鼠卵丘扩展的卵母细胞旁分泌因子及其信号通路。使用逆转录聚合酶链反应（RT-PCR）发现，卵母细胞表达两种激活素亚基，抑制素βA（Inhba）和抑制素βB（Inhbb），并且激活素A和激活素B均能使促卵泡激素（FSH）诱导的去卵母细胞（OOX）复合体的卵丘扩展。卵泡抑素是一种激活素结合蛋白，可中和激活素诱导的扩展，但对卵母细胞诱导的扩展没有影响。GDF9和激活素的I型受体分别是激活素受体样激酶5（ALK5）和ALK4，二者均激活相同的SMAD 2/3信号通路。我们使用ALK 4/5/7抑制剂SB-431542检测了该信号系统的需求。SB-431542完全消除了FSH刺激的GDF9、激活素A、激活素B以及卵母细胞诱导的卵丘扩展。此外，SB-431542还拮抗表皮生长因子刺激的、卵母细胞诱导的卵丘扩展。使用实时RT-PCR，SB-431542还减弱了GDF9、激活素A以及卵母细胞诱导的OOX中透明质酸合酶2、肿瘤坏死因子α诱导蛋白6、前列腺素合酶2和五聚素3的表达。本研究提供了证据表明，CEEF由通过SMAD 2/3信号传导的TGFB超家族分子组成，从而启动小鼠卵丘扩展。
