Time-lapse imaging with liquid crystal polarized light (LC-PolScope) and fluorescent speckle microscopy (FSM) enabled this study of spindle microtubules in monoastral spindles that were produced in crane-fly spermatocytes through flattening-induced centrosome displacement. Monoastral spindles are found in several other contexts: after laser ablation of one of a cell's two centrosomes (in the work of Khodjakov et al.), in Drosophila “urchin” mutants (in the works of Heck et al. and of Wilson et al.), in Sciara males (in the works of Fuge and of Metz), and in RNAi variants of Drosophila S2 cells (in the work of Goshima et al.). In all cases, just one pole has a centrosome (the astral pole); the other lacks a centrosome (the anastral pole). Thus, the question: How is the anastral half-spindle, lacking a centrosome, constructed? We learned that monoastral spindles are assembled in two phases: Phase I assembles the astral half-spindle composed of centrosomal microtubules, and Phase II assembles microtubules of the anastral half through extension of new microtubule polymerization outward from the spindle's equatorial mid-zone. That process uses plus ends of existing centrosomal microtubules as guiding templates to assemble anastral microtubules of opposite polarity. Anastral microtubules slide outward with their minus ends leading, thereby establishing proper bipolarity just like in normal biastral spindles that have two centrosomes.

中文翻译：

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反平行微管的滑动驱动单星纺锤体的双极化

使用液晶偏振光 (LC-PolScope) 和荧光散斑显微镜 (FSM) 进行延时成像，使这项研究能够对鹤蝇精母细胞中通过扁平化诱导的中心体位移产生的单星体纺锤体中的纺锤体微管进行研究。单星纺锤体还存在于其他几种情况中：在激光消融细胞的两个中心体之一后（在 Khodjakov 等人的工作中），在果蝇“海胆”突变体中（在 Heck 等人和 Wilson 等人的工作中） .)、Sciara雄性（Fuge 和 Metz 的工作）以及果蝇S2 细胞的 RNAi 变体（Goshima 等人的工作）。在所有情况下，只有一个极有中心体（星极）；另一个缺乏中心体（星状极）。因此，问题是：缺乏中心体的星状半纺锤体是如何构建的？我们了解到单星体纺锤体的组装分两个阶段：第一阶段组装由中心体微管组成的星体半纺锤体，第二阶段通过新的微管聚合从纺锤体的赤道中区向外延伸来组装星体半纺锤体的微管。该过程使用现有中心体微管的正端作为引导模板来组装相反极性的星体微管。星状微管以其负端领先的方式向外滑动，从而建立适当的双极性，就像具有两个中心体的正常偏向纺锤体一样。