Developmental Signals - Sonic hedgehog

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(SHH) A secreted growth factor that binds patched (ptc) receptor on cell membrane. This protein has many different functions in different tissues of the developing embryo, the main role would be of establishing "pattern". SHH name derives from homology to the original fruitfly (drosophila) "hedgehog" mutation, where these flies have hairs located in regions (ventral) which are normally hair-free, and therefore have a disrupted body pattern.

Sonic Hedgehog (SHH) was isolated by homology to the Hh gene. SHH is a true signaling switch used in differentiating subpopulations of cells throughout the embryo. Depending on where the signal is being secreted, how far away the responsive cell population is and how SHH is proteolytically cleaved, will determine SHH function. SHH binds to the membrane receptors Patched (ptc) and BOC/CDON.

Nomenclature note lower case shh for other species, upper case SHH in humans.


Developmental patterning signal.


SHH is secreted by the notochord, ventralizes the neural tube, inducing the floor plate and motor neurons.

  • neural crest cell survival in the foregut endoderm of jaw development PNAS


SHH is secreted by the zone of polarizing activity (ZPA) organizing limb axis formation.


SHH is secreted by the forebrain neuroectoderm and the facial ectoderm for upper face and nasofrontal bud development. PMID: 15979605


SHH has still others roles in organ development in lung, pancreas.

Signaling pathway

The secreted protein binds to the cell surface membrane protein the patched receptor (ptc).


Cite this page: Hill, M.A. (2020, January 18) Embryology Developmental Signals - Sonic hedgehog. Retrieved from

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© Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G