The Measure of Success: Constraints, Objectives, and Tradeoffs in Morphogen-mediated Patterning
- Departments of Developmental and Cell Biology, Mathematics and Biomedical Engineering, and Center for Complex Biological Systems, University of California, Irvine, California 92697-2300
- Correspondence: adlander{at}uci.edu
Abstract
A large, diverse, and growing number of strategies have been proposed to explain how morphogen gradients achieve robustness and precision. We argue that, to be useful, the evaluation of such strategies must take into account the constraints imposed by competing objectives and performance tradeoffs. This point is illustrated through a mathematical and computational analysis of the strategy of self-enhanced morphogen clearance. The results suggest that the usefulness of this strategy comes less from its ability to increase robustness to morphogen source fluctuations per se, than from its ability to overcome specific kinds of noise, and to increase the fraction of a morphogen gradient within which robust threshold positions may be established. This work also provides new insights into the longstanding question of why morphogen gradients show a maximum range in vivo.
Footnotes
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Editors: James Briscoe, Peter Lawrence, and Jean-Paul Vincent
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Additional Perspectives on Generation and Interpretation of Morphogen Gradients available at www.cshperspectives.org
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↵* The stabilizing effects of DFz2 on the Wg gradient do not necessarily mean that DFz2 is not a clearance receptor for Wg. As Eldar et al. (2003) point out, SEC in the Wg gradient requires an “active” mechanism, wherein Wg signaling regulates some process that influences the efficiency of Wg removal. Although they suggested that DFz2 might sequester a protease, recent work suggests that regulation of accessory molecules such as notum or dally-like, that have marked effects on Wg gradient formation (Giraldez et al. 2002; Han et al. 2005), could be involved.
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