A study of an egg-activating molecule in the sperm cytoplasm

在我们的研究中，我们发现了以下主要结果。蝾螈（Cynops pyrrhogaster）的未受精卵在第二个减数分裂中期被捕获。[Ca^<2+>]_i的短暂增加由受精精子触发，并以Ca^<2+>波的形式在卵子皮层传播，是导致卵子激活的主要信号。将Cynops精子提取物（SE）注射到未受精卵中，诱导波浪状的[Ca^<2+>]_i升高，随后卵被激活并恢复减数分裂。在se注射的卵中，不仅细胞周期蛋白B1降解，而且DNA复制得到证实。注射前将SE煮沸或用蛋白酶K处理，使其失去激活鸡蛋的活性。在se注射前预注射Ca^<2+>-螯合剂BAPTA抑制卵子活化。这些结果表明，精子细胞质中的一种热不稳定蛋白因子诱导了卵子激活所必需的[Ca^<2+>]_i的短暂增加。未受精卵注射IP_3可引起[Ca^<2+>]_i升高，激活卵子，而注射cadp -核糖则无此作用。此外，预注射肝素（一种IP_3受体抑制剂）可阻止受精精子或se注射激活卵子。结果表明，除受精外，硒注射通过IP_3受体诱导[Ca^<2+>]_i升高，而不是通过titan rianodine受体。

In our study, we have found the following major results. Unfertilized eggs of the newt, Cynops pyrrhogaster, are arrested at the second meiotic metaphase. A transient increase of [Ca^<2+>]_i, which is triggered by fertilizing sperm and propagates over the egg cortex as Ca^<2+> wave, is a primary signal to cause egg activation. The injection of an extract of Cynops sperm (SE) into the unfertilized eggs induced the wave-like [Ca^<2+>]_i increase, and then the eggs underwent activation and resumption of meiosis. In the SE-injected eggs, not only degradation of cyclin B1, but also DNA replication was confirmed. When SE had been boiled or treated with Proteinase K before injection, the activity to cause egg activation was lost. Preinjection of Ca^<2+>-chelator BAPTA before SE-injection inhibited egg activation. These results indicate that a heat-labile and proteinous factor in sperm cytoplasm induces a transient increase of [Ca^<2+>]_i indispensable for egg activation. Injection of IP_3 into unfertilized eggs caused [Ca^<2+>]_i increase and egg activation, but injection of cADP-ribose did not. In addition, preinjection of heparin, an inhibitor of IP_3 receptors, prevented egg activation by fertilizing sperm or by SE-injection. These results indicate that not only fertilization, but also SE-injection induces [Ca^<2+>]_i increase through the IP_3 receptors, rather titan rianodine receptors.