Frescas David, Mavrakis Manos, Lorenz Holger, Delotto Robert, Lippincott-Schwartz Jennifer
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
J Cell Biol. 2006 Apr 24;173(2):219-30. doi: 10.1083/jcb.200601156.
Drosophila melanogaster embryogenesis begins with 13 nuclear division cycles within a syncytium. This produces >6,000 nuclei that, during the next division cycle, become encased in plasma membrane in the process known as cellularization. In this study, we investigate how the secretory membrane system becomes equally apportioned among the thousands of syncytial nuclei in preparation for cellularization. Upon nuclear arrival at the cortex, the endoplasmic reticulum (ER) and Golgi were found to segregate among nuclei, with each nucleus becoming surrounded by a single ER/Golgi membrane system separate from adjacent ones. The nuclear-associated units of ER and Golgi across the syncytial blastoderm produced secretory products that were delivered to the plasma membrane in a spatially restricted fashion across the embryo. This occurred in the absence of plasma membrane boundaries between nuclei and was dependent on centrosome-derived microtubules. The emergence of secretory membranes that compartmentalized around individual nuclei in the syncytial blastoderm is likely to ensure that secretory organelles are equivalently partitioned among nuclei at cellularization and could play an important role in the establishment of localized gene and protein expression patterns within the early embryo.
黑腹果蝇胚胎发育始于合胞体中的13个核分裂周期。这会产生超过6000个细胞核，在接下来的分裂周期中，这些细胞核在被称为细胞化的过程中被包裹在质膜内。在本研究中，我们探究分泌膜系统如何在数千个合胞体细胞核之间平均分配，为细胞化做准备。细胞核到达皮层后，内质网（ER）和高尔基体在细胞核之间分离，每个细胞核被一个与相邻细胞核分开的单一内质网/高尔基体膜系统包围。合胞体胚盘上与细胞核相关的内质网和高尔基体单位产生分泌产物，这些产物以空间受限的方式输送到整个胚胎的质膜。这一过程发生在细胞核之间没有质膜边界的情况下，并且依赖于中心体衍生的微管。合胞体胚盘中围绕单个细胞核分隔的分泌膜的出现，可能确保分泌细胞器在细胞化时在细胞核之间平均分配，并可能在早期胚胎中局部基因和蛋白质表达模式的建立中发挥重要作用。
