Halet Guillaume, Viard Patricia, Carroll John
Department of Physiology, University College London, Gower Street, London WC1E 6BT, UK.
Development. 2008 Feb;135(3):425-9. doi: 10.1242/dev.014894. Epub 2007 Dec 19.
Mammalian preimplantation embryos develop in the oviduct as individual entities, and can develop and survive in vitro, in defined culture media lacking exogenous growth factors or serum. Therefore, early embryos must generate intrinsic signals that promote their development and survival. In other cells, activation of class I phosphoinositide 3-kinase (PI3K) is a universal mechanism to promote cell proliferation and survival. Here, we examined whether PI3K is intrinsically activated during preimplantation development. Using GFP-tagged pleckstrin homology domains to monitor PtdIns(3,4,5)P(3) synthesis, we show that PI3K is constitutively activated in mouse preimplantation embryos. E-cadherin ligation promotes PtdIns(3,4,5)P(3) synthesis at sites of blastomere adhesion at all cleavage stages. In addition, in culture conditions that promote autocrine signalling, a second pool of PtdIns(3,4,5)P(3) is generated in the apical membrane of early stage blastomeres. We show that constitutive PtdIns(3,4,5)P(3) synthesis is necessary for optimal development to blastocyst and to prevent large-scale apoptosis at the time of cavitation.
哺乳动物植入前胚胎在输卵管中作为独立个体发育，并且能够在缺乏外源性生长因子或血清的特定培养基中体外发育和存活。因此，早期胚胎必须产生促进其发育和存活的内在信号。在其他细胞中，I类磷酸肌醇3激酶（PI3K）的激活是促进细胞增殖和存活的普遍机制。在此，我们研究了PI3K在植入前发育过程中是否被内在激活。利用绿色荧光蛋白标记的普列克底物蛋白同源结构域监测磷脂酰肌醇（3,4,5）三磷酸（PtdIns(3,4,5)P(3)）的合成，我们发现PI3K在小鼠植入前胚胎中持续被激活。E-钙黏蛋白连接在所有卵裂阶段的卵裂球黏附部位促进PtdIns(3,4,5)P(3)的合成。此外，在促进自分泌信号传导的培养条件下，早期卵裂球的顶膜会产生第二池PtdIns(3,4,5)P(3)。我们表明，持续的PtdIns(3,4,5)P(3)合成对于最佳发育至囊胚以及防止空泡化时的大规模细胞凋亡是必要的。
