Cell-Size-Dependent Spindle Elongation in the Caenorhabditis elegans Early Embryo
Cell-Size-Dependent Spindle Elongation in the Caenorhabditis elegans Early Embryo
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DOI：
10.1016/j.cub.2009.07.050
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发表时间：
2009-09-29
期刊：
影响因子：
9.2
通讯作者：
Kimura, Akatsuki
中科院分区：
文献类型：
--
作者：
Hara, Yuki;Kimura, Akatsuki
细胞大小是控制细胞内结构大小的关键参数之一。一个众所周知的例子是恒定的核质比（N/C 比）[1-5]。中期纺锤体的长度与细胞大小成正比，但在早期胚胎发生期间有上限[6]。在后期，有丝分裂纺锤体伸长并将中心体和姐妹染色单体输送到新生子细胞的中心附近。在这里，我们量化了秀丽隐杆线虫早期胚胎中纺锤体伸长和细胞大小之间的关系，并提出了细胞大小依赖性纺锤体伸长的可能模型。定量测量表明，纺锤体伸长的程度和速度与整个早期胚胎发生过程中的细胞大小相关。 RNAi 敲低 G α 蛋白及其调节因子表明，纺锤体未能完全伸长，并且无论细胞大小如何，纺锤体伸长的速度几乎恒定。我们的结果表明，纺锤体伸长由两种性质不同的机制控制，即 G α 依赖性和非 G α 依赖性伸长模式。仿真分析表明，恒定拉力模型和力发生器限制模型分别再现了 G α 独立和 G α 依赖机制的动力学。这些模型还解释了如何实现主轴的设定长度。
Cell size is one of the critical parameters controlling the size of intracellular structures. A well-known example is the constant nuclear-to-cytoplasmic ratio (N/C ratio) [1-5]. The length of the metaphase spindle is proportional to cell size, but it has an upper limit during early embryogenesis [6]. During anaphase, the mitotic spindle elongates and delivers the centrosomes and sister chromatids near the centers of the nascent daughter cells. Here, we quantified the relationship between spindle elongation and cell size in the early embryo of Caenorhabditis elegans and propose possible models for cell-size-dependent spindle elongation. Quantitative measurements revealed that the extent and speed of spindle elongation are correlated with cell size throughout early embryogenesis. RNAi knockdown of G alpha proteins and their regulators revealed that the spindles failed to fully elongate and that the speed of spindle elongation was almost constant regardless of cell size. Our results suggest that spindle elongation is controlled by two qualitatively distinct mechanisms, i.e., G alpha-dependent and -independent modes of elongation. Simulation analyses revealed that the constant-pulling model and the force-generator-limited model reproduced the dynamics of the G alpha-independent and G alpha-dependent mechanisms, respectively. These models also explain how the set length of spindles is achieved.