Paddy M R, Saumweber H, Agard D A, Sedat J W
Center for Structural Biology and Department of Anatomy and Cell Biology, University of Florida, Gainesville, FL 32610-0235, USA.
J Cell Sci. 1996 Mar;109 ( Pt 3):591-607. doi: 10.1242/jcs.109.3.591.
Time-resolved, two-component, three-dimensional fluorescence light microscopy imaging in living Drosophila early embryos is used to demonstrate that a large fraction of the nuclear envelope lamins remain localized to a rim in the nuclear periphery until well into metaphase. The process of lamin delocalization and dispersal, typical of 'open' forms of mitosis, does not begin until about the time the final, metaphase geometry of the mitotic spindle is attained. Lamin dispersal is completed about the time that the chromosomal movements of anaphase begin. This pattern of nuclear lamina breakdown appears to be intermediate between traditional designations of 'open' and 'closed' mitoses. These results thus clarify earlier observations of lamins in mitosis in fixed Drosophila early embryos, clearly showing that the observed lamin localization does not result from a structurally defined 'spindle envelope' that persists throughout mitosis. During this extended time interval of lamin localization in the nuclear periphery, the lamina undergoes an extensive series of structural rearrangements that are closely coupled to, and likely driven by, the movements of the centrosomes and microtubules that produce the mitotic spindle. Furthermore, throughout this time the nuclear envelope structure is permeable to large macromolecules, which are excluded in interphase. While the functional significance of these structural dynamics is not yet clear, it is consistent with a functional role for the lamina in mitotic spindle formation.
在活的果蝇早期胚胎中进行的时间分辨、双组分、三维荧光光学显微镜成像表明，很大一部分核被膜核纤层蛋白在核周缘一直定位在边缘，直到中期。核纤层蛋白的去定位和分散过程，即典型的“开放”形式的有丝分裂，直到有丝分裂纺锤体达到最终的中期形态时才开始。核纤层蛋白的分散在后期染色体运动开始时完成。这种核纤层解体模式似乎介于传统的“开放”和“封闭”有丝分裂的定义之间。因此，这些结果澄清了早期在固定的果蝇早期胚胎中有丝分裂中对核纤层蛋白的观察，清楚地表明观察到的核纤层蛋白定位不是由在整个有丝分裂过程中持续存在的结构定义的“纺锤体包膜”导致的。在核纤层蛋白在核周缘定位的这段延长的时间间隔内，核纤层经历了一系列广泛的结构重排，这些重排与产生有丝分裂纺锤体的中心体和微管的运动密切相关，并可能由其驱动。此外，在这段时间里，核被膜结构对大分子是可渗透的，而在间期大分子是被排除在外的。虽然这些结构动力学的功能意义尚不清楚，但这与核纤层在有丝分裂纺锤体形成中的功能作用是一致的。
