![](//upload.wikimedia.org/wikipedia/commons/thumb/5/52/Shh_structure.png/220px-Shh_structure.png)
Sonic hedgehog is a protein that in humans is encoded by the SHH ("sonic hedgehog") gene. Both the gene and the protein may also be found notated alternatively as "Shh".
Sonic hedgehog is one of three proteins in the mammalian signaling pathway family called hedgehog, the others being desert hedgehog (DHH) and Indian hedgehog (IHH). SHH is the best studied ligand of the hedgehog signaling pathway. It plays a key role in regulating vertebrate organogenesis, such as in the growth of digits on limbs and organization of the brain. Sonic hedgehog is the best established example of a morphogen as defined...