Our laboratory is interested in the problem of how cells move; this research is relevant to the aberrant cell motility exhibited in metastasis and to transendothelial cell migration involved in aspects of the inflammatory response. The intellectual challenge is to relate global descriptions of cell movement and force production to molecular mechanisms. We have completed a kinematic description accounting for how locomoting fish scale keratocytes maintain constant shape and speed. This model accounts for not only dynamic morphological behavior but also the behavior of the cytoskeletal meshwork and cell surface receptors. We have also developed the first quantitative assay for the strength and pattern of the traction forces exerted by moving cells and shown how the traction pattern exhibited by keratocytes can be explained. We have investigated the adhesive contacts the motile cell makes to the substratum and how intracellular calcium is involved in traction force production by regulating cell contractility and/or adhesion.
Ongoing work involves locally perturbing cell locomotion using single cell photomanipulative techniques that are operative on the micron distance scale and 100s of ms time scale as a complement to genetic manipulation. Such techniques include chromophore assisted laser inactivation [CALI] to selectively inhibit the function of molecules responsible for cell migration and adhesion and photoactivation to quickly increase the concentration of proteins or peptides that regulate the actin cytoskeleton or signal transduction pathways important for migration. Where possible our data will be used to check the predictive power of quantitative in silico models of cell locomotion developed by our theoretical collaborators.
Our efforts in cell migration have resulted in the laboratory participating in the NIH Cell Migration Consortium within the Imaging and Photomanipulation Initiative. Papers describing our studies have been published in Nature, Nature Cell Biology, J. Cell Biol., J. Biol. Chem., Cell Motility and the Cytoskeleton and Biophys. J.
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Gliding Fish Keratocyte on Glass Substratum |
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Before uncaging NBT-II cells move on collagen matrix (18 hours after reseeding, 1 hour recovery after microinjection). After two 200 msec consecutive laser irradiations (green dots indicate irradiation spots) lamellar protrusion was temporarily inhibited in the cells loaded with caged peptide (red lines indicate the initial position of the cell lamellipodium). |
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After uncaging |
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Phase contrast, video image of a fish epidermal keratocyte (cell outlined in black) locomoting towards the right on a bead-decorated, flexible silicone rubber substratum. Superimposed over the cell is the traction map (black arrows) generated for this experiment, which is based on the analysis of bead displacements in the substratum. Tim Oliver, Micah Dembo, and Ken Jacobson; Traction Forces in Locomoting Cells; Cell Motility and the Cytoskeleton 31:225-240, 1995. |
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Gliding keratocyte on elastic substrate traction maps
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