Hedgehog signalling: how to get from Smo to Ci and Gli

The secreted morphogens of the Hedgehog family have important roles in normal development as well as in associated pathologies, including cancer. The Hedgehog signalling pathway has been studied in Drosophila and is thought to be conserved in vertebrates. Hedgehog elicits a signalling response that activates Smoothened (Smo). There is evidence of differences between Drosophila and vertebrates concerning signalling downstream of Smo, as well as in Smo itself. Here, we discuss this evidence and its importance for investigations of the pathway and related biology, as well as for the development of drugs targeting components of the pathway for treatment of associated pathologies.