Laboratory of Molecular Biology of the Cell, UMR5239, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique, 69007 Lyon, France.
J Cell Biol. 2013 May 27;201(5):653-62. doi: 10.1083/jcb.201210110. Epub 2013 May 20.
During the first embryonic division in Caenorhabditis elegans, the mitotic spindle is pulled toward the posterior pole of the cell and undergoes vigorous transverse oscillations. We identified variations in spindle trajectories by analyzing the outwardly similar one-cell stage embryo of its close relative Caenorhabditis briggsae. Compared with C. elegans, C. briggsae embryos exhibit an anterior shifting of nuclei in prophase and reduced anaphase spindle oscillations. By combining physical perturbations and mutant analysis in both species, we show that differences can be explained by interspecies changes in the regulation of the cortical Gα-GPR-LIN-5 complex. However, we found that in both species (1) a conserved positional switch controls the onset of spindle oscillations, (2) GPR posterior localization may set this positional switch, and (3) the maximum amplitude of spindle oscillations is determined by the time spent in the oscillating phase. By investigating microevolution of a subcellular process, we identify new mechanisms that are instrumental to decipher spindle positioning.
在秀丽隐杆线虫的第一次胚胎分裂过程中，有丝分裂纺锤体被拉向细胞的后端，并经历剧烈的横向振荡。我们通过分析其近亲秀丽隐杆线虫的向外相似的单细胞胚胎来识别纺锤体轨迹的变化。与秀丽隐杆线虫相比，秀丽隐杆线虫胚胎在前期表现出核的向前移位和后期纺锤体振荡减少。通过在两个物种中结合物理干扰和突变分析，我们表明差异可以通过物种间皮层 Gα-GPR-LIN-5 复合物调节的变化来解释。然而，我们发现，在两个物种中：（1）一个保守的位置开关控制着纺锤体振荡的开始；（2）GPR 后端定位可能设定了这个位置开关；（3）纺锤体振荡的最大幅度取决于振荡阶段所花费的时间。通过研究一个亚细胞过程的微观进化，我们确定了新的机制，这些机制对阐明纺锤体定位至关重要。
