Module 1: Figure stimuli for developmental signalling
Stimuli that regulate development act through a number of cell signalling pathways.
The Hedgehog proteins and Wnts are stimuli that control development. They both use a seven-membrane-spanning receptor that resembles the G protein-coupled receptor used by other signalling systems, but in this case the receptor has evolved to activate other signalling pathways. In the case of Hedgehog, the smoothened (SMO) receptor engages a transducing complex that activates the transcription factor GLI1. The signalling pathways for Wnts are carried out by Frizzled (Fz) receptors that are coupled to different signalling pathways. Some of the Wnts activate the transcription factor β-catenin, whereas other Wnts bind to Fz receptors that relay information to other signalling pathways.