Reimer C L, Crawford B J
Department of Anatomy, University of British Columbia, Vancouver.
Dev Biol. 1995 Feb;167(2):439-57. doi: 10.1006/dbio.1995.1040.
The unfertilized oocyte contains various granules which serve as storage sites for proteins, the majority which are yolk granules or platelets. Yolk granules are thought to provide the developing embryo with nutrients essential for its survival, while other granules contain proteins such as enzymes and extracellular matrix components that are required for fertilization and perhaps for early development. This study uses immunofluorescence and immunogold techniques with two novel monoclonal antibodies against proteins found in egg yolk and cortical granules to study the localizations of these antigens during early starfish development. Partial biochemical characterizations using the anti-yolk antibody have revealed that there are a family of structurally related proteins in oocyte yolk granules and that while the molecular compositions of the yolk proteins change during embryogenesis, their depletion is not significant until the larval stage, suggesting these proteins are not required for early development. In addition, a large immunoreactive protein has been found in the intestine and coelomic fluid, suggesting that, as in other species, the starfish yolk proteins may be derived from a large precursor, such as vitellogenin. Analysis of the anti-cortical granule antibody has revealed that a 120-kDa antigen is stored in antibody has revealed that a 120-kDa antigen is stored in cortical granules of unfertilized eggs. Upon egg activation, the cortical granules located in the peripheral egg cytoplasm undergo exocytosis, and the 120-kDa antigen is released into the perivitelline space. However, other granules, which are also labeled by this antibody, remain dispersed throughout the egg cytoplasm and are still present in the early gastrula, where they appear to contribute to the extracellular matrices of the developing embryo. This suggests that starfish cortical granules play a dual function: At fertilization, where they help create a block to polyspermy, and in embryonic development, where they secrete extracellular matrix components.
未受精的卵母细胞含有各种颗粒，这些颗粒作为蛋白质的储存位点，其中大多数是卵黄颗粒或血小板。卵黄颗粒被认为为发育中的胚胎提供生存所必需的营养物质，而其他颗粒则含有蛋白质，如受精以及可能早期发育所需的酶和细胞外基质成分。本研究使用免疫荧光和免疫金技术，结合两种针对卵黄和皮质颗粒中发现的蛋白质的新型单克隆抗体，来研究这些抗原在海星早期发育过程中的定位。使用抗卵黄抗体进行的部分生化特性分析表明，卵母细胞卵黄颗粒中存在一族结构相关的蛋白质，并且虽然卵黄蛋白的分子组成在胚胎发生过程中会发生变化，但直到幼虫阶段它们的消耗才显著，这表明这些蛋白质在早期发育中并非必需。此外，在肠道和体腔液中发现了一种大量的免疫反应性蛋白质，这表明，与其他物种一样，海星卵黄蛋白可能源自一种大的前体，如卵黄生成素。对抗皮质颗粒抗体的分析表明，一种120 kDa的抗原储存在未受精卵的皮质颗粒中。卵子激活后，位于卵周质外周的皮质颗粒会发生胞吐作用，120 kDa的抗原会释放到卵周隙中。然而，也被这种抗体标记的其他颗粒仍分散在整个卵细胞质中，并且在早期原肠胚中仍然存在，它们似乎对发育中胚胎的细胞外基质有贡献。这表明海星皮质颗粒具有双重功能：在受精时，它们有助于形成多精受精阻断；在胚胎发育中，它们分泌细胞外基质成分。
