Tolic-Nørrelykke Iva M, Sacconi Leonardo, Stringari Chiara, Raabe Isabel, Pavone Francesco S
European Laboratory for Nonlinear Spectroscopy, Via Nello Carrara 1, 50019 Sesto Fiorentino (Florence), Italy.
Curr Biol. 2005 Jul 12;15(13):1212-6. doi: 10.1016/j.cub.2005.05.052.
The position of the division plane affects cell shape and size, as well as tissue organization. Cells of the fission yeast Schizosaccharomyces pombe have a centrally placed nucleus and divide by fission at the cell center. Microtubules (MTs) are required for the central position of the nucleus. Genetic studies lead to the hypothesis that the position of the nucleus may determine the position of the division plane. Alternatively, the division plane may be positioned by the spindle or by morphogen gradients or reaction diffusion mechanisms. Here, we investigate the role of MTs in nuclear positioning and the role of the nucleus in division-plane positioning by displacing the nucleus with optical tweezers. A displaced nucleus returned to the cell center by MT pushing against the cell tips. Nuclear displacement during interphase or early prophase resulted in asymmetric cell division, whereas displacement during prometaphase resulted in symmetric division as in unmanipulated cells. These results suggest that the division plane is specified by the predividing nucleus. Because the yeast nucleus is centered by MTs during interphase but not in mitosis, we hypothesize that the establishment of the division plane at the beginning of mitosis is an optimal mechanism for accurate symmetric division in these cells.
分裂平面的位置会影响细胞的形状和大小，以及组织的组织结构。裂殖酵母粟酒裂殖酵母的细胞具有位于中央的细胞核，并在细胞中心通过裂变进行分裂。微管（MTs）对于细胞核的中央位置是必需的。遗传学研究提出了这样的假设，即细胞核的位置可能决定分裂平面的位置。或者，分裂平面可能由纺锤体、形态发生素梯度或反应扩散机制定位。在这里，我们通过用光学镊子移动细胞核来研究微管在细胞核定位中的作用以及细胞核在分裂平面定位中的作用。被移动的细胞核通过微管向细胞尖端施加推力而回到细胞中心。在间期或前期早期进行细胞核移位会导致细胞不对称分裂，而在前中期进行移位则会导致如未处理细胞那样的对称分裂。这些结果表明，分裂平面由即将分裂的细胞核确定。由于酵母细胞核在间期由微管居中，但在有丝分裂期间并非如此，我们推测在有丝分裂开始时建立分裂平面是这些细胞进行精确对称分裂的一种最佳机制。
