Distinct expression of two types of XenopusPatched genes during early embryogenesis and hindlimb development

Patched (Ptc) is a putative twelve transmembrane domain protein that is both a Hedgehog (Hh) receptor and transcriptional target of Hh. In this study, we isolated Xenopus Ptc cDNAs, Ptc-1 and Ptc-2, and carried out comparative analyses on their expression patterns. The putative Ptc-2 protein has a long C-terminal extension that has similarities in both length and sequence to those of Ptc-1 proteins in mouse, chick and human. In both early embryogenesis and hindlimb development, Ptc-2 expression is restricted to cells that receive a Hh signal, a pattern similar to that of Gli-1. Ptc-1, however, shows a broader distribution, mainly non-overlapping with that of Ptc-2. Despite the difference in their expression patterns, both are induced in animal cap explants synergistically by Shh and Noggin, showing a conserved regulation in their activation mechanisms.