Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, 5650871, Japan.
Graduate School of Medicine, Osaka University, Suita, Osaka, 5650871, Japan.
Sci Rep. 2018 Jan 22;8(1):1315. doi: 10.1038/s41598-018-19497-6.
Sperm entry in mammalian oocytes triggers intracellular Ca oscillations that initiate resumption of the meiotic cell cycle and subsequent activations. Here, we show that phospholipase C zeta 1 (PLCζ1) is the long-sought sperm-borne oocyte activation factor (SOAF). Plcz1 gene knockout (KO) mouse spermatozoa fail to induce Ca changes in intracytoplasmic sperm injection (ICSI). In contrast to ICSI, Plcz1 KO spermatozoa induced atypical patterns of Ca changes in normal fertilizations, and most of the fertilized oocytes ceased development at the 1-2-cell stage because of oocyte activation failure or polyspermy. We further discovered that both zona pellucida block to polyspermy (ZPBP) and plasma membrane block to polyspermy (PMBP) were delayed in oocytes fertilized with Plcz1 KO spermatozoa. With the observation that polyspermy is rare in astacin-like metalloendopeptidase (Astl) KO female oocytes that lack ZPBP, we conclude that PMPB plays more critical role than ZPBP in vivo. Finally, we obtained healthy pups from male mice carrying human infertile PLCZ1 mutation by single sperm ICSI supplemented with Plcz1 mRNA injection. These results suggest that mammalian spermatozoa have a primitive oocyte activation mechanism and that PLCζ1 is a SOAF that ensures oocyte activation steps for monospermic fertilization in mammals.
精子进入哺乳动物卵母细胞会引发细胞内钙离子振荡，从而启动减数分裂细胞周期的恢复和随后的激活。在这里，我们表明，磷脂酶 C ζ1（PLCζ1）是长期寻找的精子携带的卵母细胞激活因子（SOAF）。Plcz1 基因敲除（KO）小鼠精子无法诱导胞质内单精子注射（ICSI）中的钙离子变化。与 ICSI 相反，Plcz1 KO 精子在正常受精中诱导了非典型的钙离子变化模式，并且由于卵母细胞激活失败或多精受精，大多数受精卵在 1-2 细胞阶段停止发育。我们进一步发现，Plcz1 KO 精子受精的卵母细胞中，透明带多精受精阻断（ZPBP）和质膜多精受精阻断（PMBP）均被延迟。由于缺乏 ZPBP 的 astacin 样金属内肽酶（Astl）KO 雌性卵母细胞中多精受精很少见，我们得出结论，PMBP 在体内比 ZPBP 发挥更关键的作用。最后，我们通过用 Plcz1 mRNA 注射补充的单精子 ICSI，从携带人类不育 PLCZ1 突变的雄性小鼠中获得了健康的幼崽。这些结果表明，哺乳动物精子具有原始的卵母细胞激活机制，而 PLCζ1 是一种 SOAF，可确保哺乳动物单精受精的卵母细胞激活步骤。
