The directionality of locomotion of mouse fibroblasts: Role of cell adhesiveness

Abstract

To evaluate the role of adhesiveness in cell locomotion we have compared the parameters of motion (rate and directionality index) of an adhesive-deficient mutant, AD6, and of its parental strain, BALB 3T3, by means of cinematography. The low adhesive cells, AD6, have the same migration rate (1 μm/min) as the parental cells, but they have lost the directionality of motion (directionality index is 6-fold lower in AD6). Similarly, the parental strain BALB 3T3 or the mutant biochemically reverted, cultured on a poorly adhesive substratum, showed a significant decrease in the persistence of direction of movement. The adhesiveness of AD6 cells is increased when cultured in presence of LETS (50 μg/ml). In these conditions the high directionality index of the wild-type cells is restored in the mutant. On the other hand, we have reported that N-acetyl glucosamine bypasses the enzymatic block of the AD6 cells, and restores to normal the cell surface carbohydrates and adhesiveness. We show here that the directionality of motion is also reverted by the amino-sugar. A good correlation was found between the loss of directionality and the absence of microfilament bundles. We conclude that adhesiveness to substratum controls the directionality of fibroblast locomotion as follows: (1) Cell-to-substrate adhesion is necessary to stabilize the leading edge and to promote the organization of microfilaments in bundles; (2) the stabilization of the leading edge and the axial organization provided by the actin cables are required for the persistence of direction of motion.