Characterisation of a second patched gene in the zebrafish Danio rerio andthe differential response of patched genes to hedgehog signalling

Hedgehog signalling has been implicated in a variety of processes in verteb rate development, and in each case, the activity of Hh proteins is thought to be mediated by their interaction with a large multipass transmembrane pr otein encoded by the patched (ptc) gene. In this study we present the full- length coding sequence and describe the wild-type expression pattern of a s econd ptc gene in zebrafish, Zf-ptc2. We End that at the sequence level Zf- ptc2 is more closely related than Zf-ptc1 to the ptc genes initially charac terised in other vertebrate species. We also show that transcription of Zf- ptc2, like Zf-ptc1, is dependent upon Hh signalling and present evidence th at it is activated in response to lower levels of Hh activity than is Zf-pt c1. In addition we find no evidence for any specificity in the regulatory i nteractions between the various Hh proteins and the two ptc genes in the ze brafish. (C) 1999 Academic Press.