Fig. 6. Expression and regulation of Gas1 in the murine first arch. (A,B) Coronal sections through the branchial regions at E11.5 (downregulation of Gas1 in odontogenic mesenchyme arrowed). (C-L) Timed culture of E11.5 mandibular mesenchyme. (C-F) Gas1 progressively downregulates in the diastema (arrowed), whereas expression is maintained in the non-odontogenic mesenchyme underlying the incisor and molar regions. (G-L). Adjacent section in situ hybridisation demonstrates progressive Gas1 downregulation (G,I,K) and Ptc1 upregulation (H,J,L) in isolated diastema mesenchyme between 18 and 24 hours of culture. (M-P) E11.5 mandibular mesenchyme cultured for 24 hours following co-electroporation of Gas1 and GFP constructs (M,N), or electroporation of a GFP construct alone (O,P). Electroporation fluorescence (M,O); Ptc1 expression (N,P). Note downregulation of Ptc1 in the presence of ectopic Gas1 expression (N, arrowed), as opposed to controls (P). Scale bars: in A, 200 µm for A,B; in C, 600 µm for C-F,M-P; in G, 600 µm for G-L.