Hedgehog trafficking, cilia and brain functions.

The primary cilium has recently emerged as an important center for transduction of the Sonic Hedgehog (Shh) signal. Genetic studies have shown that Shh signaling at the level of primary cilia is essential for patterning the ventral neural tube and regulating adult stem cells. Some defects observed in human diseases and resulting from mutations affecting the organization of the primary cilium have been attributed to defective Shh signaling. The recent development of Shh pathway inhibitors for treating tumors linked to perturbations of Shh signaling has fostered studies to understand their mechanism of action in Shh receptor complex trafficking at the primary cilium.