Positional Information


The concept of positional information proposes that cells acquire positional values as in a coordinate system, which they interpret by developing in particular ways to give rise to spatial patterns. Some of the best evidence for positional information comes from regeneration experiments, and the patterning of the vertebrate limb. Central problems are how positional information is set up, how it is recorded and then how it is interpreted by the cells. A number of models have been proposed for the setting up of positional gradients, and most are based on diffusion of a morphogen and its interactions with extracellular molecules; however, diffusion may not be reliable mechanism. There are also mechanisms based on timing. There is no good evidence for the quantitative aspects of any of the proposed gradients and details of how they are set up.

Key Concepts

  • Pattern is the spatial organisation of the embryo.
  • Positional information proposes that cells acquire positional values as in a coordinate system, which they interpret by developing in particular ways to give rise to spatial patterns.
  • Morphogens are chemical gradients that might provide positional Information.
  • Position can be specified by a timing mechanism.
  • Turing spatial models are based on reaction diffusion and can generate repeated forms.

Keywords: pattern formation; embryo; positional information; morphogen; gradients; cytonemes; reaction–diffusion; turing‐like mechanism

Figure 1. The French flag model. Each cell in the line has the potential to develop into a red, white or blue cell. A gradient in a morphogen together with thresholds can result in the development of the French flag. Reproduced with permission from Wolpert et al. () © Oxford University Press.


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Wolpert, Lewis(Sep 2016) Positional Information. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0020914.pub2]