Cell Biology and Biophysics Unit and 2 Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.
J Cell Biol. 2012 Jun 25;197(7):887-95. doi: 10.1083/jcb.201204019. Epub 2012 Jun 18.
In the early embryo of many species, comparatively small spindles are positioned near the cell center for subsequent cytokinesis. In most insects, however, rapid nuclear divisions occur in the absence of cytokinesis, and nuclei distribute rapidly throughout the large syncytial embryo. Even distribution and anchoring of nuclei at the embryo cortex are crucial for cellularization of the blastoderm embryo. The principles underlying nuclear dispersal in a syncytium are unclear. We established a cell-free system from individual Drosophila melanogaster embryos that supports successive nuclear division cycles with native characteristics. This allowed us to investigate nuclear separation in predefined volumes. Encapsulating nuclei in microchambers revealed that the early cytoplasm is programmed to separate nuclei a distinct distance. Laser microsurgery revealed an important role of microtubule aster migration through cytoplasmic space, which depended on F-actin and cooperated with anaphase spindle elongation. These activities define a characteristic separation length scale that appears to be a conserved property of developing insect embryos.
在许多物种的早期胚胎中，相对较小的纺锤体被定位在细胞中心附近，以便随后进行胞质分裂。然而，在大多数昆虫中，核分裂迅速发生，没有胞质分裂，核迅速分布在整个大合胞体胚胎中。核在胚胎皮层中的均匀分布和锚定对于胚胎胚层的细胞化至关重要。核在合胞体中分散的原则尚不清楚。我们从单个黑腹果蝇胚胎中建立了一种无细胞系统，该系统支持具有天然特征的连续核分裂周期。这使我们能够在预定的体积内研究核分离。将核包封在微室中表明，早期细胞质被编程为将核分离一定的距离。激光显微手术揭示了微管星体通过细胞质空间迁移的重要作用，这取决于 F-肌动蛋白，并与后期纺锤体伸长合作。这些活动定义了一个特征分离长度尺度，这似乎是发育中的昆虫胚胎的一个保守特性。
