Developmentally regulated cell surface alterations in Dictyostelium discoideum

Abstract

THE life cycle of the cellular slime mould, Dictyostelium discoideum, can be divided into two mutually exclusive phases¹. The vegetative state, in which the cells divide by fission every few hours, is characterised by the absence of intracellular communication; whereas the developmental social state, which is initiated by the exhaustion of nutrients, exhibits many forms of such interactions. These include the ability to respond to and relay chemotactic signals², and to form stable species-specific cell to cell contacts^3–5. The ability to form stable cell contacts can develop in the absence of a chemotactic gradient, as demonstrated by the immediate formation of normal aggregates upon plating of cells which have been maintained in suspension in a nutrient-free salt solution for 8–9 h (ref. 1). New antigens appear and function on the cell surface during development^3,4. Gerisch and his coworkers have shown that univalent antibodies directed against the surface of 12 h cell aggregates interfere specifically with the formation of the stable cell to cell contacts^4–6. Furthermore, it has been demonstrated that a developmentally controlled, heat-stable component, which is present in membrane preparations from 12 h aggregates, interferes specifically with the morphological and biochemical development of the organism (J.E.S., and J. Tuchman, unpublished, and J. Tuchman et al., unpublished).