Integrins as architects of cell behaviour

Integrins are cell surface receptors that bind cells to their physical external envi- ronment, linking the extracellular matrix to cell function. They are essential in the biology of all animals. In the late 1980s, we discovered that integrins are required for the ability of breast epithelia to do what they are programmed to do, which is to differentiate and make milk. Since then, integrins have been shown to control most other aspects of phenotype: to stay alive, to divide, and to move about. Integrins also provide part of the mechanism that allows cells to form tissues. Here I discuss how we discovered that integrins control mam- mary gland differentiation and explore the role of integrins as central architects of other as- pects of cell behavior.