Figure 5.

Paracrine SHH signaling in taste papillae epithelium and stroma. SHH ligand is present in Type IV basal cells and signals to Gli1+ and Ptch1+ HH-responding cells in the anterior tongue fungiform and posterior circumvallate papilla epithelium and stroma. Black arrows indicate epithelial paracrine signaling, and red arrows indicate neural paracrine signaling. In the fungiform papilla, epithelial SHH drives signaling in basal cells, perigemmal cells, and stromal cells (black arrows), while neural SHH signals to stromal cells (red arrow) (Note that neural paracrine signaling within the taste bud also has been suggested [108]). On the other hand, in the circumvallate papilla, epithelial SHH-responding targets are predominantly basal and perigemmal cells (black arrows), while neural SHH can target both basal and stromal cells (red arrows).