Alonso-Latorre B, Meili R, Bastounis E, Del Alamo J C, Firtel R, Lasheras J C
Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093-0411, USA.
Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:3346-9. doi: 10.1109/IEMBS.2009.5333191.
Amoeboid motility results from the cyclic repetition of shape changes leading to periodic oscillations of the cell length (motility cycle). We analyze the dominant modes of shape change and their association to the traction forces exerted on the substrate using Principal Component Analysis (PCA) of time-lapse measurements of cell shape and traction forces in migrating Dictyostelium cells. Using wild-type cells (wt) as reference, we investigated Myosin II activity by studying Myosin II heavy chain null cells (mhcA-) and Myosin II essential light chain null cells (mlcE-). We found that wt, mlcE-and mhcA- cells utilize similar modes of shape changes during their motility cycle, although these shape changes are implemented at a slower pace in Myosin II null mutants. The number of dominant modes of shape changes is surprisingly few with only four modes accounting for 75% of the variance in all cases. The three principal shape modes are dilation/elongation, bending, and bulging of the front/back. The second mode, resulting from sideways protrusion/retraction, is associated to lateral asymmetries in the cell traction forces, and is significantly less important in mhcA- cells. These results indicate that the mechanical cycle of traction stresses and cell shape changes remains remarkably similar for all cell lines but is slowed down when myosin function is lost, probably due to a reduced control on the spatial organization of the traction stresses.
阿米巴样运动源于形状变化的周期性重复，导致细胞长度的周期性振荡（运动周期）。我们使用对迁移的盘基网柄菌细胞的细胞形状和牵引力进行延时测量的主成分分析（PCA），来分析形状变化的主导模式及其与施加在基质上的牵引力的关联。以野生型细胞（wt）作为对照，我们通过研究肌球蛋白II重链缺失细胞（mhcA-）和肌球蛋白II必需轻链缺失细胞（mlcE-）来探究肌球蛋白II的活性。我们发现，wt、mlcE-和mhcA-细胞在其运动周期中利用相似的形状变化模式，尽管这些形状变化在肌球蛋白II缺失突变体中进行得较慢。形状变化的主导模式数量出奇地少，在所有情况下仅有四种模式占方差的75%。三种主要的形状模式是扩张/伸长、弯曲以及前端/后端的鼓起。由侧向突出/缩回导致的第二种模式与细胞牵引力的侧向不对称相关，并且在mhcA-细胞中重要性显著降低。这些结果表明，所有细胞系的牵引应力和细胞形状变化的机械循环仍然非常相似，但当肌球蛋白功能丧失时会减慢，这可能是由于对牵引应力空间组织的控制减弱所致。
