Shh Maintains Dermal Papilla Identity and Hair Morphogenesis via a Noggin–Shh Regulatory Loop

The document from June 1, 2012, details a study on the role of Sonic hedgehog (Shh) signaling in hair follicle morphogenesis, particularly focusing on the dermal papilla (DP) and dermal cells (DC). The research demonstrated that Shh signaling is essential for maintaining DP identity and hair morphogenesis by inducing the expression of Noggin, a BMP antagonist, in DCs. The study found that loss of Smoothened (Smo) function in the dermis led to the loss of DP precursors and arrested hair follicle development, which could be partially rescued by overexpressing Noggin. This suggests a critical Noggin-Shh regulatory loop in hair follicle morphogenesis. Additionally, the study showed that Shh signaling regulates a subset of DP signature genes without affecting dermal proliferation, indicating specific functions of dermal Smo in maintaining DP cell identity and maturation. The findings imply that disrupting the Noggin-Shh loop could have therapeutic implications for cancers involving this pathway. The study was conducted using mouse models and did not involve human subjects.