Mehlmann L M, Terasaki M, Jaffe L A, Kline D
Department of Biological Sciences, Kent State University, Ohio 44242, USA.
Dev Biol. 1995 Aug;170(2):607-15. doi: 10.1006/dbio.1995.1240.
The endoplasmic reticulum (ER) of live metaphase II mouse eggs and prophase I-arrested oocytes was compared using the fluorescent, lipophilic dicarbocyanine dye, DiI. DiL, dissolved in soybean oil, was microinjected into oocytes and eggs; the dye diffused throughout the cytoplasm to label the ER, which was imaged by confocal microscopy. The mature egg had a fine reticular network of ER throughout the cell and numerous dense accumulations of membrane in the cortex. These ER accumulations, 1-2 microns in diameter, were generally absent deeper in the cytoplasm. A similar staining pattern was observed when the eggs were fixed within 1 min of injection, providing evidence that the cortical accumulations of membrane are part of a continuous ER membrane system, since membrane trafficking could not occur in a fixed egg. Cortical ER accumulations were localized to the same region of the egg as the cortical granules and were not observed in the cortical granule-free region adjacent to the meiotic spindle. In contrast, ER accumulations were rarely found in the cortex of the immature, prophase I-arrested oocyte, but larger and less well-defined membrane clusters were found throughout the deeper cytoplasm of the oocyte. The appearance of ER clusters in the egg cortex following oocyte maturation correlates with an increased ability of the mature egg to release calcium at fertilization. Since the ER is a calcium store, structural reorganization of the ER may be necessary to permit the large release of calcium and resulting cortical granule exocytosis at fertilization.
利用荧光亲脂性双羰花青染料DiI，对处于有丝分裂中期II的活小鼠卵母细胞和处于减数分裂前期I停滞状态的卵母细胞的内质网（ER）进行了比较。将溶解于大豆油中的DiI显微注射到卵母细胞和卵子中；染料扩散到整个细胞质中，标记内质网，然后通过共聚焦显微镜成像。成熟卵子在整个细胞内有精细的内质网网状网络，在皮质中有大量密集的膜聚集物。这些内质网聚集物直径为1 - 2微米，通常在细胞质较深处不存在。在注射后1分钟内固定卵子时，观察到类似的染色模式，这表明皮质膜聚集物是连续内质网膜系统的一部分，因为在固定的卵子中不会发生膜运输。皮质内质网聚集物与皮质颗粒位于卵子的同一区域，而在减数分裂纺锤体相邻的无皮质颗粒区域未观察到。相比之下，在未成熟的减数分裂前期I停滞的卵母细胞皮质中很少发现内质网聚集物，但在卵母细胞较深的细胞质中发现了更大且界限不那么清晰的膜簇。卵母细胞成熟后卵子皮质中内质网簇的出现与成熟卵子在受精时释放钙的能力增强相关。由于内质网是钙储存库，内质网的结构重组可能是受精时允许大量钙释放并导致皮质颗粒胞吐所必需的。
