In Discoglossus pictus eggs, only the dimple contains ionic channels active at fertilization; in particular, chloride channels are found in the central portion of the dimple, which is also the site of sperm penetration. Moreover the dimple hosts an imposing cytoskeleton, consisting of a cortical network and bundles of microfilaments extending from the microvilli. Since spectrin cross links actin and is connected through ankyrin to anion transporters in the plasma membrane of erythrocytes as well as to anion channels in other cells, we studied, in D. pictus egg, the relationship between the localization of spectrin and the high polarization of ionic channels and cytoskeletal organization. By means of immunocytochemistry, we localized spectrin exclusively in the egg dimple. In an attempt to trace back the source of spectrin localization, we immunostained sections of D. pictus ovary and localized spectrin in the nuclei of previtellogenic oocytes, where actin is also present. Antispectrin staining remained until germinal vesicle breakdown. By contrast, a cortical localization was found only when the oocytes divided into two hemispheres and into the germinative area (GA), which, after germinal vesicle breakdown, gives rise to the dimple. At this stage the antispectrin signal was particularly strong in the GA. Using Rho-pialloidin, we also established that spectrin is generally present where F-actin is found. However, spectrin and F-actin do not have the same pattern of fluorescence. In conclusion, our data suggest that spectrin may play a role in oocyte and egg polarity. In eggs, it could be instrumental in anchoring to the cytoskeleton membrane proteins such as receptors and ionic channels, including chloride-permeable channels.

译文

:在盘pic蛋中,只有酒窝中含有在受精时活跃的离子通道;特别地,在酒窝的中央部分发现了氯离子通道,这也是精子穿透的部位。此外,酒窝有一个气势旺盛的细胞骨架,由皮质网络和从微绒毛延伸出来的微丝束组成。由于血影蛋白交联肌动蛋白并通过锚蛋白连接至红细胞质膜中的阴离子转运蛋白以及其他细胞中的阴离子通道,因此我们在D. pictus卵中研究了血影蛋白的定位与高蛋白极化之间的关系。离子通道和细胞骨架组织。通过免疫细胞化学,我们将血影蛋白仅定位在蛋酒窝中。为了追溯血影蛋白定位的来源,我们对D. pictus卵巢的切片进行了免疫染色,并在前玻璃化卵母细胞的核中定位了血影蛋白,那里也存在肌动蛋白。保留抗谱蛋白染色直至生发囊泡破裂。相比之下,仅当卵母细胞分为两个半球并进入发芽区域(GA)时才发现皮层定位,在发芽囊泡破裂后会形成酒窝。在此阶段,GA中的抗谱蛋白信号特别强。使用Rho-pialloidin,我们还确定在发现F-肌动蛋白的地方通常存在血影蛋白。然而,血影蛋白和F-肌动蛋白没有相同的荧光模式。总之,我们的数据表明血影蛋白可能在卵母细胞和卵的极性中起作用。在卵中,它可能有助于锚定细胞骨架膜蛋白,例如受体和离子通道,包括氯离子可渗透通道。

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