Fig. 1

The Canonical activation of Shh pathway in vertebrates. The activation occurs by ligand-dependent interaction when Shh binds to Ptch at the cell membrane. In response to this binding, Ptch no longer inhibits Smo, which accumulates at the PC and initiates the downstream signaling pathway cascade. So, Smo regulates the Gli processing and activation at the PC. When Gli is activated, it translocates to the nucleus, where it activates target genes. (Diagram by Carballo, VC). (Adapted from Robbins et al., 2012) [54]