Fig. 1.

Ptch-binding and signaling activities of HPE mutant ShhN proteins. (A) Sequences of human ShhN, mouse ShhN, rat ShhN, Xenopus Banded hedgehog (Bhh), Drosophila Hh, and mouse Desert hedgehog (Dhh) are aligned with nonidentical residues in blue. Human and mouse sequences are identical except for a Ser in place of Thr at position 67 in the human sequence; the numbering of corresponding human and mouse residues differs by one because of different signal sequence lengths. Residues altered in human HPE are boxed in yellow, and the altered residues are shown above in green. (B) Binding of altered ShhN mutant proteins to the Ptch receptor. Binding of ³²P-ShhN to EcR-293 cells stably expressing Ptch-CTD (15) was measured in the presence of unlabelled recombinant proteins; binding was normalized to the amount (100%) bound in absence of any competitor. (C) Signaling activities of altered ShhN proteins in intermediate neural plate explants from chick embryos. After incubation in presence of recombinant proteins (concentrations in nM are indicated by the numbers in each panel), explants were double stained with antibodies against Pax-7 (green) and the floor plate marker HNF3-β (red).