Epithelial cells make contact with extracellular matrix via receptors on the basal surface that
interact with the basal actin cortex. In 3D matrix, the mesenchymal cell makes contact with
matrix all around its circumference via similar receptors. When moving, the fibroblast is
constantly constructing a new front end. We postulate in a 'fixed cortex'theory of cell motility
that the circumferential actin cortex is firmly attached to matrix and that the myosin-rich
endoplasm slides past it into the continually forming new front end. During epithelial …