Finally, pathways such as Wnt signaling are very complex and involve a number of different ligands, receptors and endogenous antagonists and the activation of distinct intracellular signaling ...

We know today that Wnt and a handful of other signalling systems (Notch, Hedgehog, TGFβ (transforming growth factor-β)–BMP (bone morphogenetic protein) and receptor tyrosine kinases ...