Suppression of positional errors in biological development.
Cells in developing embryos behave according to their positions in the organism, and therefore seem to be receiving 'positional information'. A widespread view of the mechanism for this is that each cell responds locally to the concentration level of some extracellular chemical which is distributed in a spatial gradient. For molecules conveying and receiving the positional signal, concentrations are likely to be low enough that, per individual cell, only a few thousand molecules may be involved. Fluctuations to be expected in these numbers (Poisson distribution) could readily lead to errors up to a few percent of embryo length in the reading of position. This is an intolerable level of error for some developmental pattern-forming events. Embryos must have means of suppressing such errors. We maintain that this requires communication between cells, and illustrate this by using the reaction part of two well-known Turing-type reaction-diffusion models as the local gradient reader. We show that switching on diffusion in these models leads to adequate suppression of positional errors.
Holloway
D M
DM
H.C. Orsted Institute, Chemistry Laboratory III, Copenhagen University, Denmark. lionel@pepe.chem.ubc.ca
Harrison
L G
LG
D000818:Animals; D002450:Cell Communication / Q000502:physiology; D004330:Drosophila / Q000196:embryology*; D004626:Embryology; D005260:Female; D008954:Models, Biological; D016012:Poisson Distribution