The fish epidermal keratocyte as a model system for the study of cell locomotion.

Keratocytes provide an excellent system for the study of locomotion because their simple shape allows the description of basic principles that govern their movement. The graded radial extension (GRE) model is a kinematic description of keratocyte locomotion which relates cell shape to movement. It predicts the circumferential motion of morphological features within the plane of the moving cell. The detection of circumferential motion allows the GRE model to be distinguished from the process of spreading and parallel extension. The circumferential motion of morphological features and the curvature of lines "photomarked" into macromolecular assemblies can be explained in terms of the regulation of actin filament dynamics. The GRE model can thus relate molecular scale events to the locomotion of a whole cell. The principles of the GRE model may operate in other cell types especially since different modes of locomotion appear to be part of the same phenomenon.