Bipedal Locomotion in Crawling Cells

Department of Biochemistry, Stanford University School of Medicine, Stanford, California, USA.
Biophysical Journal (Impact Factor: 3.97). 03/2010; 98(6):933-42. DOI: 10.1016/j.bpj.2009.10.058
Source: PubMed


Many complex cellular processes from mitosis to cell motility depend on the ability of the cytoskeleton to generate force. Force-generating systems that act on elastic cytoskeletal elements are prone to oscillating instabilities. In this work, we have measured spontaneous shape and movement oscillations in motile fish epithelial keratocytes. In persistently polarized, fan-shaped cells, retraction of the trailing edge on one side of the cell body is out of phase with retraction on the other side, resulting in periodic lateral oscillation of the cell body. We present a physical description of keratocyte oscillation in which periodic retraction of the trailing edge is the result of elastic coupling with the leading edge. Consistent with the predictions of this model, the observed frequency of oscillation correlates with cell speed. In addition, decreasing the strength of adhesion to the substrate reduces the elastic force required for retraction, causing cells to oscillate with higher frequency at relatively lower speeds. These results demonstrate that simple elastic coupling between movement at the front of the cell and movement at the rear can generate large-scale mechanical integration of cell behavior.

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    • "We further assume that some internal mechanism (stiffness of the cell cortex [45] [46] [47] [48] [49] [50], osmotic pressure actively controlled by the channels and pumps on the cell membrane [51] [52], etc.) maintains a given size L 0 = l + − l − of the cell. Therefore the stress at the edges must be the same σ(l − (t), t) = σ(l + (t), t) = σ 0 , where σ 0 (t) is then an unknown function. "
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    • "For wildtype and scrA − cells, we found that the cell length and strain energy oscillations are highly correlated, suggesting that the regulation of the cycle depends on the ability of the cell to modulate its length and to generate traction stresses. We confirmed that the average period of the oscillations in the cell length (and strain energy) for wild-type and scrA − cells is inversely proportional to the cell's average migration speed, in agreement with our previous findings for cell movement on gelatin substrates (del Álamo et al., 2007; Meili et al., 2010) and with experimental measurements and theoretical models obtained for crawling keratocytes (Barnhart et al., 2010). This correlation is also consistent with the view that the average speed of migration of the cell is determined by the frequency at which it can perform its motility cycle. "
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