A limb bud morphogen bites the dust

Hedgehog signaling has traditionally been considered to be a morphogen for digits. In this issue of Develop-mental Cell, Zhu et al. show that a brief exposure to Sonic Hedgehog is sufficient for digit specification, and this finding suggests that it is not acting as a direct morphogen but rather as an initiator of this process.

Automated summary

A brief exposure to Sonic Hedgehog is shown to be sufficient for digit specification, suggesting that Hedgehog signaling is not acting as a direct morphogen but rather as an initiator of this process.