Abstract

In Dictyostelium discoideum , a multicellular organism stems from individual amoebae in response to nutrient depletion. Despite the vastly different strategy used to generate multicellular structures, processes associated with animal development including cell sorting, pattern formation and cell-type choice are mirrored to a remarkable degree in the development of Dictyostelium . Morphogenesis ultimately leads to the formation of a fruiting body composed of dormant spores mounted on a rigid stalk of dead cells. The simplicity of this dichotomous choice makes Dictyostelium a model system for the study of pattern formation in developing organisms. Several lines of evidence suggest that cell-type biases are directly linked to the cell cycle. Cells starved early in the cell cycle preferentially become the stalk cells while those starved in later phases of the cell cycle favour the spore pathway [Weijer, C., Duschl, G., David, C.N. (1984) J. Cell Sci ., 70 , 133-145; MacDonald, S.A., Durston, A.J. (1984) J. Cell Sci ., 66 , 195-204; Gomer, R.H., Firtel, R.A. (1987) Science , 237 , 758-762; Ohmori, T., Maeda, Y. (1987) Cell Differentiation , 25 , 11-18; Zimmerman, W., Weijer, C. (1993) Developmental Biology , 160 , 178-185; Araki, T., Hajime, N., Takeuchi, I., Maeda, Y. (1994) Developmental Biology , 162 , 221-228]. The underlying mechanism linking the cell cycle to cellular differentiation is unclear. To gain a better understanding of the relationship we have undertaken the analysis of proteins controlling the cell division cycle. In this work we describe a mutation in Cdc2 kinase, a pivotal cell cycle control element, and demonstrate that the cell-cycle control mechanism contributes directly to cell-type biases.