Enhanced Shh signaling in <i>Ptch1</i>^{<i>Wig/Wig</i>} mutants affects cranial placode development.

<p>(A and D) Immunostaining of PAX3 (green), SOX10 (red), and DAPI (blue) in wild type (A) and <i>Ptch1</i>^<i>Wig</i> mutants (D). PAX3-positive cells (placodal cells) and PAX3/SOX10 double-positive cells (neural crest cells) are identified by green and white arrowheads respectively. (B, C, E and F) <i>Pax3</i> mRNA expression in control (B and C) vs. <i>Ptch1</i>^<i>Wig</i> mutants (E and F). Sections in (C and F) correspond to the dotted line in (B and E). Red arrowheads indicate reduced <i>Pax3</i> expression in <i>Ptch1</i>^{<i>Wig/Wig</i>} mutant placodal primordia (E, F vs. B, C). (G-L) Whole mount <i>in situ</i> hybridization of indicated placodal markers <i>Ngn1</i> (G and J), <i>Ngn2</i> (H and K), and <i>NeuroD1</i> (I and L) on E9.5 wild type (G-I) vs. <i>Ptch1</i>^<i>Wig</i> mutants (J-L). Red and white arrowheads identify the trigeminal and epibranchial placodes respectively. Scale bars: 20μm (A and D); 100μm (B,E and G-L); 50μm (C and F).