Increased Shh signaling in <i>Ptch1</i>^<i>Wig</i> mutants resulted in less cellular interaction between neural crest and placodal cells.

<p>(A-D) <i>Wnt1Cre;R26RYFP</i> fate mapping in control wild type (A and B) and <i>Ptch1</i>^{<i>Wig/Wig</i>} mutants (C and D) at E9.5. The YFP fate-mapped cells were identified by GFP immunostaining (green) and neurogenic placode cells were identified by TUJ1 staining (red) in the opthalamic (A and C) and facial nerve (B and D) region. The section planes in A-D are the same as those indicated in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0120821#pone.0120821.g003" target="_blank">Fig. 3B,C,F and G</a>. <i>Ptch1</i>^{<i>Wig/Wig</i>} mutants (C and D) displayed much less neural crest cell (green) admixture within the ophthalmic and geniculate placodes relative to controls (A and B). Scale bars: 20μm (A and C); 50μm (B and D).