Growth factors as morphogens: do gradients and thresholds establish body plan?
Theories of morphogenesis have centred around gradients of morphogens interpreted by cells according to preset concentration thresholds. Growth factor proteins have been candidates for such morphogens, and experiments in the frog Xenopus, among other organisms, now show that embryonic cells are capable of interpreting growth factor concentrations according to the models. This opens up questions of whether such mechanisms are sufficient, and-if there are growth factor gradients-which factors are actually used and how.
National Institute for Medical Research, Mill Hill, London, UK.
J B
JB
Green
J C
JC
Smith
D000818:Animals; D004268:DNA-Binding Proteins / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000502:physiology; D004627:Embryonic Induction; D005314:Embryonic and Fetal Development; D005801:Genes, Homeobox; D005809:Genes, Regulator; D006133:Growth Substances / Q000494:pharmacology / Q000502:physiology*; D008648:Mesoderm / Q000502:physiology; D009024:Morphogenesis / Q000187:drug effects / Q000502:physiology*; D009994:Osmolar Concentration; D014714:Vertebrates / Q000196:embryology; D014981:Xenopus / Q000196:embryology
D004268:DNA-Binding Proteins; D006133:Growth Substances