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Zusammenfassung:
The use of mathematical modelling to formulate and test theories is still quite rare in biology. It has now been applied to show how a robust, sharp peak of signalling molecules can be formed in developing fruitfly embryos.
It was proposed many years ago that, during animal development, graded concentration profiles of signalling molecules could provide information telling cells where they are in the embryo and what they should do. Since then, many examples of such molecules — known generically as morphogens — have been found1,2. Concentration gradients can be generated through the production of morphogens at a particular source, followed by their diffusion and degradation in appropriate regions. Often, sharp peaks occur in the distribution of morphogens, which might suggest that they require a sharply localized source. But in fact nature has circumvented this requirement, as can be seen from the development of the dorsal–ventral (back-to-belly) body axis in insects and vertebrates, where the source is plateau-like. The question of how this leads to a sharp concentration peak is difficult to tackle by traditional experimental means, as the system contains many variables. On page 304 of this issue, Eldar and colleagues3 describe how they used mathematical modelling to address the problem, and carried out experiments to back up their predictions.
