Obox4-silencing-activated STAT3 and MPF/MAPK signaling accelerate nuclear membrane breakdown in mouse oocytes
Obox4-silencing-activated STAT3 and MPF/MAPK signaling accelerate nuclear membrane breakdown in mouse oocytes
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DOI：
10.1530/rep-15-0020
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发表时间：
2016-04-01
期刊：
影响因子：
3.8
通讯作者：
Lee, Kyung-Ah
中科院分区：
文献类型：
--
作者：
Lee, Hyun-Seo;Kim, Kyeoung-Hwa;Lee, Kyung-Ah
小鼠卵母细胞从卵泡中分离后开始体外成熟。以前，我们表明，卵母细胞特异性同源框4（Obox 4）是维持完整的核膜的胚泡（GV）在卵母细胞和完成减数分裂中期I-II（MI-MII）过渡的关键。本研究进一步探讨了OBOX 4调控GV核膜破裂的分子机制。成熟促进因子（MPF）和丝裂原活化蛋白激酶（MAPK）在GV期卵母细胞中通常是无活性的，但在体外经3-异丁基-1-甲基黄嘌呤（IBMX）处理后，它们在GV期卵母细胞中被过早激活。此外，信号转导和转录激活因子3（STAT 3）被Obox 4 RNAi显著激活。我们证实，这种Obox 4 RNAi诱导的过早的STAT 3和MPF/MAPK在GV阶段的激活引起随后的GV破坏（GVBD），尽管在补充IBMX的培养基中高cAMP的相反力维持完整的GV。当卵丘-卵母细胞复合体暴露于干扰素α（IFNA）（一种STAT 3激活剂）时，卵母细胞成熟，卵丘细胞在补充IBMX的培养基中扩增以恢复核成熟，这表明STAT 3激活足以刺激减数分裂的继续。使用Stattic，一种特异性的STAT 3抑制剂，我们证实了GVBD涉及在Obox 4沉默的卵母细胞中的STAT 3激活。基于这些发现，我们得出结论：i）Obox 4是MPF/MAPK和STAT 3信号传导的重要上游调节剂，并且ii）Obox 4是卵母细胞中GV停滞机制的关键调节剂。
Mouse oocytes begin to mature in vitro once liberated from ovarian follicles. Previously, we showed that oocyte-specific homeobox 4 (Obox4) is critical for maintaining the intact nuclear membrane of the germinal vesicle (GV) in oocytes and for completing meiosis at the metaphase I-II (MI-MII) transition. This study further examines the molecular mechanisms of OBOX4 in regulating GV nuclear membrane breakdown. Maturation-promoting factor (MPF) and MAPK are normally inactive in GV stage oocytes but were activated prematurely in arrested GV stage oocytes by 3-isobutyl-1-metyl-xanthine (IBMX) in vitro after Obox4 RNA interference (RNAi). Furthermore, signal transducer and activator of transcription 3 (STAT3) was significantly activated by Obox4 RNAi. We confirmed that this Obox4 RNAi-induced premature STAT3 and MPF/MAPK activation at the GV stage provoked subsequent GV breakdown (GVBD) despite the opposing force of high cAMP in the IBMX-supplemented medium to maintain intact GV. When cumulus-oocyte complexes were exposed to interferon alpha (IFNA), a STAT3 activator, oocytes matured and cumulus cells expanded to resume nuclear maturation in IBMX-supplemented medium, suggesting that STAT3 activation is sufficient for stimulating the continuation of meiosis. Using Stattic, a specific STAT3 inhibitor, we confirmed that GVBD involves STAT3 activation in Obox4-silenced oocytes. Based on these findings, we concluded that i) Obox4 is an important upstream regulator of MPF/MAPK and STAT3 signaling, and ii) Obox4 is a key regulator of the GV arrest mechanism in oocytes.