Figure 2.

Hh signaling components in the (a) FGP and (b) CVP. Building on Figure 1, Hh signaling components are located in FGP and CVP. Within the epithelium of taste organs, Shh is principally restricted in taste bud cells, but Shh expression is also in nerve fibers of the tongue and FGP or CVP core, identified with mouse reporter lines (B.L. Allen, A.A. Dlugosz, A. Kumari, C.M. Mistretta, unpublished data). Gli1⁺, Ptch1⁺, and Gli2⁺ cells are within the basal layer of the epithelium of the lateral FGP walls, in perigemmal and apical extragemmal cells, and in stromal cells of the papilla core. Gli2⁺ cells also extend in basal epithelial cells beyond the FGP. The inset illustrates paracrine signaling flow from Shh⁺ taste bud cells to Hh-responding cells in the lateral papilla walls, perigemmal and apical extragemmal cells, to stromal cells, and from Shh⁺ nerves to fibroblasts/stromal cells. Within the CVP, Gli1⁺, Ptch1⁺, and Gli2⁺ cells are within the basal layer of the papilla epithelium, in perigemmal and apical extragemmal cells, and in stromal cells of the papilla core. Paracrine signaling from Shh⁺ cells within the taste bud to Hh-responding cells is proposed similar to the FGP. Abbreviations: CVP, circumvallate papillae; FGP, fungiform papillae; Hh, Hedgehog; Shh, Sonic Hedgehog.