Distribution of traction forces associated with shape changes during amoeboid cell migration

• Published in: 2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society Vol. 2009; pp. 3346 - 3349
• Main Authors: Alonso-Latorre, B., Meili, R., Bastounis, E., del Alamo, J.C., Firtel, R., Lasheras, J.C.
• Format: Conference Proceeding Journal Article
• Language: English
• Published: United States IEEE 01.01.2009
• Subjects: actin polymerization; Actins - chemistry; Adhesives; Animals; Biophysics - methods; Cell Adhesion; cell migration; Cell Motility; Cell Movement; Cell Shape; Cells (biology); Dictyostelium; Embryo; Force measurement; Leukocytes - cytology; Myosin Type II - chemistry; Polymers; Principal Component Analysis; Shape control; Shape measurement; Signal Processing, Computer-Assisted; Stress control; Stress, Mechanical; Time Factors; traction stresses; USA Councils
• ISSN: 1094-687X; 1557-170X; 1558-4615
• 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.