Modelling of Dictyostelium discoideum slug migration.

The development of most multicellular organisms involves differential movement of cells resulting in the formation of tissues. The principles governing these movements are poorly understood. One exception is the formation of the slug in the social amoebae Dictyostelium discoideum. The slug forms by the chemotactic aggregation of up to 10(5) starving cells, it is motile and migrates in response to light and temperature gradients to the surface of the soil to form a fruiting body consisting of a stalk supporting a spore head. Slug migration and behaviour result from coordinated chemotactic movement of the individual cells in the slug. Waves of a chemoattractant, most likely cAMP, are periodically initiated in the tip of the slug and propagate towards the back of the slug resulting in periodic forward movement of individual cells as well as the whole slug. Here we develop a model to investigate how wave propagation and cell movement interacts to result in migration and shape changes of the slug. The slug tissue is modelled as an incompressible liquid, in which waves of chemoattractant are generated in an excitable manner. The liquid is "active", i.e. it is able to generate body forces in response to the gradients of the chemoattractant. These forces lead to the formation of flows (representing chemotactically moving cells) and result in slug movement and shape changes. The model provides a theoretical framework for the understanding of the interactions between cell-cell signalling and cell movement, which govern slug behaviour and tissue morphogenesis.