Longing for Ligand: Hedgehog, Patched, and Cell Death

The hedgehog signaling pathway controls crucial events during development. In a Perspective, Guerrero and Ruiz i Altaba discuss new work ( Thibert et al .) that identifies the Ptc1 receptor for Sonic hedgehog as a crucial modulator of programmed cell death during development of the chick neural tube. Ptc1 joins a cadre of other receptors, called ligand dependence receptors, that induce the programmed cell death of cells bearing them if they remain unoccupied by ligand.