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. 2002 Dec 15;16(24):3173–3185. doi: 10.1101/gad.1035602

Figure 5.

Figure 5

Figure 5

Effects of FGF4 beads on the expression of selected marker genes in explanted molar rudiments of E13.5 Lef1−/− embryos. Gene expression was monitored by whole-mount in situ hybridization after 1–4 d of incubation. (A) Application of FGF4-soaked beads or BSA-soaked control beads to the mutant tooth germs. After 1 d, strong expression of Fgf3 in the mesenchyme and weak expression of Shh in the epithelium was detected. After 4 d, Shh and Fgf9 are expressed in the epithelium, Fgf3 and Bmp4 in the mesenchyme. Note two expression domains of Fgf3: one close to the bead, the other in the mesenchymal papilla surrounded by the epithelial cap. Very rarely, weak Fgf4 expression was seen, as in one of the two explants shown here. None of these genes is activated by control beads soaked in BSA (mesenchymal expression of Bmp4 is not affected in the mutant; see Fig. 1A). (B) Time course of gene activation by FGF4 in explanted molar rudiments or in isolated molar mesenchyme of E14.5 Lef1−/− embryos. Fgf3 transcription is activated within 3 h, even in the absence of dental epithelium. Shh expression is undetectable after 16 h (weak signals are seen after 24 h; see A), and strong signals are observed in the epithelium after 48 h. As expected, Shh transcription is not activated in the mesenchyme.