Fig. 1

Regulation of Tbx1 expression in the early secondary palate. Wholemount in situ hybridization on palatal shelf explants cultured for 24 h in the presence or absence of the Shh inhibitor cyclopamine and the Fgf receptor inhibitor SU5402. a Tbx1 is expressed in the palatal shelf epithelium and first molar tooth germ (arrowed); (b) in the absence of Shh signaling, Tbx1 is maintained; (c) in the absence of Fgf signaling, Tbx1 is lost; (d) Shh signaling is active in the developing palate and first molar (arrowed) as shown by expression of the Shh transcriptional target patched1 (Ptch1); (e) in the presence of cyclopamine Ptch1 transcription is lost; (f) Fgf signaling is active in the developing palate and first molar (arrowed), as shown by expression of the Fgf transcriptional target sprouty2 (Spry2); (g) in the presence of SU4502 Spry2 is lost. Lines mark the medial edge of the palatal shelf