CELL-DIVISION IN DICTYOSTELIUM WITH SPECIAL EMPHASIS ON ACTOMYOSIN ORGANIZATION IN CYTOKINESIS
CELL-DIVISION IN DICTYOSTELIUM WITH SPECIAL EMPHASIS ON ACTOMYOSIN ORGANIZATION IN CYTOKINESIS
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DOI：
10.1002/cm.970180105
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发表时间：
1991-01-01
影响因子：
--
通讯作者：
INOUE, S
中科院分区：
文献类型：
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作者：
FUKUI, Y;INOUE, S
本研究重点关注盘状 D. discoideum 胞质分裂过程中肌动蛋白和肌球蛋白（“传统”肌球蛋白或肌球蛋白-II）的动态重组。这是首次鉴定网柄菌纺锤体微管的双折射以及三组微丝结构的研究。使用配备偏振光 (POL) 和微分干涉衬度 (DIC) 光学器件并结合数字图像处理的通用偏光显微镜，通过视频显微镜实时跟踪这些纤维结构的组织变化。通过半同步培养获得高频有丝分裂细胞，并利用琼脂覆盖法进行高分辨率观察（Yumura等：Journal of Cell Biology 99：894-899，1984）。双折射结构的分子特性通过荧光显微镜测定。以 0.3 微米景深的轴向分辨率进行离焦观察。肌动球蛋白原纤维在整个有丝分裂过程中显示出显着的重组。领先的板状伪足的原纤维消失，并且在前中期皮质肌动球蛋白出现显着的组装，这伴随着细胞体积的减小。皮质肌动球蛋白在后期逐渐增加。后期后期后，形成非常活跃的极片状伪足，平均寿命不到 1 分钟。我们证实极片状伪足包含肌动蛋白，但不包含肌球蛋白-II。在卵裂沟处，微丝来自两种独特的结构：赤道处的圆形收缩环和平行于极轴的皮质丝阵列。肌球蛋白位于收缩环中，但与 F-肌动蛋白的轴向阵列无关。收缩环中的肌动球蛋白逐渐转变为子细胞后部区域的皮质网络。沟槽的构建伴随着水的剧烈流出，这一点可以通过高度活跃的收缩液泡形成和与沟槽相连的微小囊泡的湍流运动来证明。这项研究证明了一种新的微丝结构的存在，以及收缩环的动态特性，并为胞质分裂背后的收缩机制提供了新的线索。
This study focuses on the dynamic reorganization of actin and myosin ("conventional" myosin, or myosin-II) during cytokinesis in D. discoideum. This is the first study identifying the birefringence of the spindle microtubules as well as three sets of microfilamentous structure in Dictyostelium. The change of organization in these fibrillar structures was followed in real-time with video microscopy, using a Universal Polarizing Microscope equipped with polarized-light (POL) and differential interference contrast (DIC) optics combined with digital image processing. High-frequency mitotic cells were obtained by semi-synchronous culture, and high-resolution observations were made by utilizing the agaroverlay method (Yumura et al.: Journal of Cell Biology 99:894-899, 1984). The molecular identity of the birefringent structures was determined by fluorescence microscopy. Through-focus observations were performed with an axial resolution of 0.3-mu-m depth of field.The actomyosin fibrils show a dramatic reorganization throughout mitosis. The fibrils at the leading lamellipodia disappear, and there is a striking assembly of the cortical actomyosin in pro-metaphase, which is accompanied by a decrease in cell volume. The cortical actomyosin gradually increases through anaphase. After late anaphase, very active polar lamellipodia, with an average life of less than 1 minute, are formed. We confirmed that the polar lamellipodia include actin, but not myosin-II. At the cleavage furrow, the microfilaments from two distinctive structures: circular contractile ring at the equator, and a cortical filament array parallel to the polar axis. Myosin is localized in the contractile ring, but not associated with the axial array of F-actin. Actomyosin in the contractile ring gradually transforms into cortical network at the posterior region of daughter cells. The construction of the furrow is accompanied by a drastic efflux of water as evidenced by highly active contractile vacuole formation and turbulent motion of minute vesicles connected to the furrow. This study demonstrates the presence of a new microfilament structure, as well as the dynamic property of the contractile ring, and sheds new light on the contractile mechanisms underlying cytokinesis.