CNRS, Institut Jacques Monod, Université de Paris, F-75006 Paris, France.
Equipe Labellisée LIGUE Contre le Cancer, Paris, France.
Proc Natl Acad Sci U S A. 2022 Feb 22;119(8). doi: 10.1073/pnas.2115593119.
Cells are filled with macromolecules and polymer networks that set scale-dependent viscous and elastic properties to the cytoplasm. Although the role of these parameters in molecular diffusion, reaction kinetics, and cellular biochemistry is being increasingly recognized, their contributions to the motion and positioning of larger organelles, such as mitotic spindles for cell division, remain unknown. Here, using magnetic tweezers to displace and rotate mitotic spindles in living embryos, we uncovered that the cytoplasm can impart viscoelastic reactive forces that move spindles, or passive objects with similar size, back to their original positions. These forces are independent of cytoskeletal force generators yet reach hundreds of piconewtons and scale with cytoplasm crowding. Spindle motion shears and fluidizes the cytoplasm, dissipating elastic energy and limiting spindle recoils with functional implications for asymmetric and oriented divisions. These findings suggest that bulk cytoplasm material properties may constitute important control elements for the regulation of division positioning and cellular organization.
细胞充满了大分子和聚合物网络，这些网络为细胞质赋予了依赖于尺度的粘性和弹性特性。尽管这些参数在分子扩散、反应动力学和细胞生物化学中的作用越来越受到重视，但它们对较大细胞器（如细胞分裂的有丝分裂纺锤体）的运动和定位的贡献仍然未知。在这里，我们使用磁镊在活胚胎中位移和旋转有丝分裂纺锤体，发现细胞质可以产生粘性弹性回复力，使纺锤体或具有相似大小的被动物体回到原来的位置。这些力与细胞骨架力发生器无关，但可达数百皮牛顿，并与细胞质拥挤程度有关。纺锤体的运动使细胞质产生切变并使其流动，耗散弹性能量并限制纺锤体的回弹，这对不对称和定向分裂具有功能意义。这些发现表明，细胞质的整体物质特性可能是调节分裂定位和细胞组织的重要控制因素。
