Physical Forces and Pattern Formation in Limb Development

Abstract

For those cells of the body whose differentiated cell type is determined while they are at one position, but which then move elsewhere to form their definitive anatomical structures, the geometry of these structures must be explained in terms of whatever physical forces are responsible for moving the cells into their eventual positions. Positional control of gene expression is not enough. The skeletal muscle cells of the limb are a good example: their cells are known to be derived originally from the somites, from which they migrate into the developing limb bud (Chevallier, Kieny and Mauger, 1977). In principle, the forces responsible might include those of growth, adhesion, active cellular locomotion or other processes; but this article is concerned specifically with the ubiquitous locomotory forces called “traction”.