The determination of spatial pattern in Dictyostelium discoideum.
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Date
1992-12
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Abstract
Free-living amoebae of the cellular slime mould Dictyostelium discoideum
aggregate when starved and give rise to a long and thin multicellular structure, the slug.
The slug resembles a metazoan embryo, and as with other embryos it is possible to specify
a fate map. In the case of Dictyostelium discoideum the map is especially simple: cells in the
anterior fifth of the slug die and form a stalk while the majority of those in the posterior
differentiate into spores. The genesis of this anterior-posterior distinction is the subject of
our review. In particular, we ask: what are the relative roles of individual pre-aggregative
predispositions and post-aggregative position in determining cell fate? We review the
literature on the subject and conclude that both factors are important. Variations in
nutritional status, or in cell cycle phase at starvation, can bias the probability that an
amoeba differentiates into a stalk cell or a spore. On the other hand, isolates, or slug
fragments, consisting of only prestalk cells or only prespore cells can regulate so as to
result in a normal range of both cell types. We identify three levels of control, each being
responsible for guiding patterning in normal development: (i) 'coin tossing', whereby a cell
autonomously exhibits a preference for developing along either the stalk or the spore
pathway with relative probabilities that can be influenced by the environment; (ii)
'chemical kinetics', whereby prestalk and prespore cells originate from undifferentiated
amoebae on a probabilistic basis but, having originated, interact (e.g. via positive and
negative feedbacks), and the interaction influences the possibility of conversion of one cell
type into the other; and (iii) 'positional information', in which the spatial distribution of
morphogens in the slug influences the pathway of differentiation. In the case of possibilities
(i) and (ii), sorting out of like cell types leads to the final spatial pattern. In the case of
possibility (iii), the pattern arises in situ.
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Keywords
Slime mould, Dictyostelium, development, pattern formation
Citation
Nanjundiah Vidyanand, Saran Shweta. The determination of spatial pattern in Dictyostelium discoideum. Journal of Biosciences. 1992 Dec; 17(4): 353-394.