PDF(Pubmed)
Abstract：
The vitelline layer (VL) of a sea urchin egg is an intricate meshwork of glycoproteins that intimately ensheathes the plasma membrane. During fertilization, the VL plays important roles. Firstly, the receptors for sperm reside on the VL. Secondly, following cortical granule exocytosis, the VL is elevated and transformed into the fertilization envelope (FE), owing to the assembly and crosslinking of the extruded materials. As these two crucial stages involve the VL, its alteration was expected to affect the fertilization process. In the present study, we addressed this question by mildly treating the eggs with a reducing agent, dithiothreitol (DTT). A brief pretreatment with DTT resulted in partial disruption of the VL, as judged by electron microscopy and by a novel fluorescent polyamine probe that selectively labelled the VL. The DTT-pretreated eggs did not elevate the FE but were mostly monospermic at fertilization. These eggs also manifested certain anomalies at fertilization: (i) compromised Ca2+ signaling, (ii) blocked translocation of cortical actin filaments, and (iii) impaired cleavage. Some of these phenotypic changes were reversed by restoring the DTT-exposed eggs in normal seawater prior to fertilization. Our findings suggest that the FE is not the decisive factor preventing polyspermy and that the integrity of the VL is nonetheless crucial to the egg\'s fertilization response.
摘要：
海胆卵的卵黄层（VL）是复杂的糖蛋白网状物，紧密包裹质膜。在受精过程中,VL起着重要的作用。首先,精子的受体位于VL上。其次,皮质颗粒胞吐后，VL升高并转化为受精包膜(FE)，由于挤出材料的组装和交联。由于这两个关键阶段涉及VL，它的改变预计会影响施肥过程。在本研究中,我们通过用还原剂温和地处理鸡蛋来解决这个问题，二硫苏糖醇(DTT)。用DTT的短暂预处理导致VL的部分破坏，通过电子显微镜和选择性标记VL的新型荧光多胺探针判断。DTT预处理的卵并没有提高FE，但在受精时大多是单精子的。这些卵在受精时也表现出某些异常：（i）Ca2信号受损，（ii）皮质肌动蛋白丝的阻断易位，和(iii)受损的卵裂。通过在受精前在正常海水中恢复暴露于DTT的卵，可以逆转其中一些表型变化。我们的研究结果表明，FE并不是阻止多精子症的决定性因素，VL的完整性对卵子的受精反应至关重要。
