Fig. 1. Expression of Shh pathway genes in the murine mandibular process. E11.5 mandibular explants cultured for 24 hours in the presence (A,C,E,G) or absence (B,D,F,H) of epithelium. (A) Shh in incisor and molar epithelium (arrowed); large arrow indicates diastema. (B) Loss of Shh in mandibular arch mesenchyme. (C) Ptc1 in the incisor and molar regions (arrowed). (D) Upregulation of Ptc1 in isolated mesenchyme (arrowed). (E) Gli1 in the incisor and molar regions (arrowed). (F) Upregulation of Gli1 in isolated mesenchyme (arrowed). (G) Hhip1 in the incisor and molar regions (arrowed). (H) Loss of Hhip1 in isolated mesenchyme. (I-L) Timed culture in the absence of epithelium. (I) Downregulation of Ptc1, principally in the molar regions (arrowed), after 12 hours. (J) Loss of Ptc1 in both the incisor and molar regions after 16 hours. (K) Upregulation of Ptc1 after 20 hours. (L) Ectopic Ptc1 expression established after 22 hours. All figures show whole-mount in situ hybridisation. Scale bar in A: 600 µm for A-L.