Traction proteins in the extracellular matrix of Dictyostelium discoideum slugs

Abstract

In developing embryos, cells interact with their environment via an extracellular matrix (ECM) which may also provide positional information and directional guidance^1,2. Such interactions are difficult to study in vivo because the ECM is inaccessible. These difficulties can be avoided with Dictyostelium discoideum. The slug of this simple multicellular organism resembles a tiny sausage whose sheath is a continuously produced ECM of cellulose and protein^3–6 through which the cells move. Behind the advancing slug, the empty sheath collapses to leave an easily accessed trail of relatively pure ECM. Here we report studies with a monoclonal antibody which reveals striking patterns in the trail of the migrating slug. These patterns contain cell prints which indicate the former positions of slug cells within the sheath. This leads us to re-evaluate how D. discoideum cells move with respect to their ECM^7,8 and to propose the existence of a class of ‘traction proteins’.