Fig. 3

The Shh signalling pathway in HFSCs. a In the absence of Shh, the complex consisting of Gli and Sufu cannot form, preventing the transcription of the target genes. b In the Shh pathway, Shh induces the release of Smo inhibition. Then, Smo can translocate into the membrane and initiate the activation and translocation of Gli into the nucleus, allowing the transcription of target genes (e.g., Ptch and Gli1), creating a feedback loop in this pathway. When the Shh ligand does not bind to its receptor, PTCH, this cascade is aborted, and Gli is sequestered in the cytoplasm via the interaction with suppressor of fused homologue (Sufu, one of the crucial inhibitors of Shh signalling). The T-shaped lines indicate inhibitory interactions involved in this pathway, and the solid arrows indicate activating interactions