Morphogen

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As morphogens are signaling molecules referred to which the pattern forming (or the morphogenesis ) during the development of multicellular creatures control. Morphogens are not evenly distributed in a tissue , but in different concentrations . They are formed at a localized source and then diffuse into the surrounding tissue. In doing so, they form concentration gradients that indirectly convey spatial position information to the neighboring cells in the tissue. Because only when certain threshold values ​​in the concentration of the morphogen are reached, the necessary genes that control development are activated in the target cell . Cells can no longer only answer yes / no reactions, but gradual reactions are enabled depending on the concentration: A high concentration of the morphogen can activate one group of genes, for example, a medium concentration activates another group and a low one Concentration activates a third group of genes. This system is also known as the French flag model . This range is sometimes referred to as the morphogenetic field .

A morphogen thus affects a whole set of cells and forces them to react differently depending on how far they are from the source of the production of the morphogen.

Some of the best studied morphogens are the proteins bicoid and hunchback , which play an important role in the early embryogenesis of the fruit fly Drosophila melanogaster . These are transcription factors that can activate other genes. Other morphogens are growth factors such as the proteins Hedgehog , Wingless or Decapentaplegic .

literature

  • Alan Turing : The chemical basis of morphogenesis (PDF; 1.2 MB). In: Philosophical Transactions of the Royal Society of London, Series B, No. 641, Vol. 237, August 14, 1952. Retrieved May 12, 2011.
  • Lewis Wolpert : Positional information and the spatial pattern of cellular differentiation. Journal of Theoretical Biology 1969, 25 (1): 1-47.
  • S. Shimozono, T. Iimura, et al. a .: Visualization of an endogenous retinoic acid gradient across embryonic development. In: Nature. Volume 496, Number 7445, April 2013, pp. 363-366, ISSN  1476-4687 . doi : 10.1038 / nature12037 . PMID 23563268 .