Hachem Alaa, Godwin Jonathan, Ruas Margarida, Lee Hoi Chang, Ferrer Buitrago Minerva, Ardestani Goli, Bassett Andrew, Fox Sebastian, Navarrete Felipe, de Sutter Petra, Heindryckx Björn, Fissore Rafael, Parrington John
Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Development. 2017 Aug 15;144(16):2914-2924. doi: 10.1242/dev.150227. Epub 2017 Jul 10.
Activation of the egg by the sperm is the first, vital stage of embryogenesis. The sperm protein PLCζ has been proposed as the physiological agent that triggers the Ca oscillations that normally initiate embryogenesis. Consistent with this, recombinant PLCζ induces Ca oscillations in eggs and debilitating mutations in the gene are associated with infertility in men. However, there has been no evidence that knockout of the gene encoding PLCζ abolishes the ability of sperm to induce Ca oscillations in eggs. Here, we show that sperm derived from male mice fail to trigger Ca oscillations in eggs, cause polyspermy and thus demonstrate that PLCζ is the physiological trigger of these Ca oscillations. Remarkably, some eggs fertilized by PLCζ-null sperm can develop, albeit at greatly reduced efficiency, and after a significant time-delay. In addition, males are subfertile but not sterile, suggesting that in the absence of PLCζ, spontaneous egg activation can eventually occur via an alternative route. This is the first demonstration that fertilization without the normal physiological trigger of egg activation can result in offspring. PLCζ-null sperm now make it possible to resolve long-standing questions in fertilization biology, and to test the efficacy and safety of procedures used to treat human infertility.
精子对卵子的激活是胚胎发生的第一个关键阶段。精子蛋白磷脂酶Cζ（PLCζ）被认为是触发正常启动胚胎发生的钙离子振荡的生理因子。与此一致的是，重组PLCζ可诱导卵子中的钙离子振荡，而该基因的功能丧失性突变与男性不育有关。然而，尚无证据表明编码PLCζ的基因敲除会消除精子诱导卵子中钙离子振荡的能力。在此，我们表明，源自基因敲除雄性小鼠的精子无法触发卵子中的钙离子振荡，会导致多精受精，从而证明PLCζ是这些钙离子振荡的生理触发因子。值得注意的是，一些由缺乏PLCζ的精子受精的卵子尽管效率大大降低且有明显的时间延迟，但仍能发育。此外，基因敲除雄性小鼠生育力低下但并非不育，这表明在没有PLCζ的情况下，自发的卵子激活最终可通过另一条途径发生。这是首次证明在没有卵子激活的正常生理触发因子的情况下受精也能产生后代。缺乏PLCζ的精子现在使得解决受精生物学中长期存在的问题以及测试用于治疗人类不育的程序的有效性和安全性成为可能。
