Figure 3.

Effects of Hh signaling suppression or inhibition on FGP morphology and Hh-responding cells. FGP diagrams illustrate Gli1lacZ⁺, Hh-responding cells (insets), for (a) control mouse tongue and (b) after Hh signaling suppression or inhibition. An H&E stained FGP image is included as an inset in a, the control diagram. This provides a comparison for images in c–f. (c–f) Four examples of papilla morphology after Hh signaling repression with taste bud cell loss are presented in H&E staining. Examples represent four different models for Hh/Gli suppression, or Smo inhibition or Smo deletion: (c) epithelial expression of a dominant negative-repressor form of Gli2 (ΔC4); (d) genetic conditional deletion of Gli2 from epithelium; (e) pharmacological blockade of Smo with the Hh pathway inhibitor LDE225; and (f) global conditional deletion of Smo. After Hh signaling suppression in all models, Hh-responding cells are eliminated in the epithelium but retained in papilla stroma (as shown in the inset in panel b from the Gli1^lacz Hh signaling reporter mouse). With Hh signaling disruption, the FGP loses an intact apical taste bud, and across models, the papilla acquires a pointed, heavily keratinized spinous apex. Abbreviations: FGP, fungiform papillae; Hh, Hedgehog; Shh, Sonic Hedgehog; Smo, smoothened receptor.