sonic hedgehog

https://doi.org/10.1351/goldbook.11232

Protein morphogen produced in the notochord that plays a critical role in early development, including vertebrate organogenesis, brain development and limb formation.

Note: Production in the embryo is dependent upon secretion of fibroblast growth factors.
Source:
PAC, 2016, 88, 713. (Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)) on page 806 [Terms] [Paper]