Fig. 4.

Gustatory ganglion cells that innervate taste buds express Shh-tdTomato. (A) Shh^CreERT2;R26R^tdTomato (Shh-tdTomato) mice were given tamoxifen daily for 4 days and harvested at 10, 60 or 85 days. (B-D) In Shh-tdTomato⁺ tongues, punctate signal (red) is evident in FFP at all times (arrowheads); at 60 and 85 days (C,D) gustatory innervation (arrows) associated with FFP (arrowheads) is also labeled. (E) Gustatory neurons in the geniculate ganglion (gVII) innervate FFP via the chorda tympani (CT) nerve, and project to the nucleus of the solitary tract (NST) in the brainstem. The greater superficial petrosal (GSP) nerve innervates soft palate taste buds (not shown). gVII neurons project centrally to the NST. (F-H) Cells in gVII express tdTomato at all time points. (I-K‴) At 60 days, PGP9.5⁺ nerve fibers (white in J,K″; green in K,K‴) innervate taste buds and adjacent FF epithelium, whereas Shh-tdTomato⁺ neurites (white in I,K′; red in K,K‴), which are also PGP9.5⁺, innervate taste buds exclusively (K′-K‴, cyan arrowheads). (L-N‴) P2X2⁺ taste fibers (white in M,N′; green in N,N‴) express Shh-tdTomato (white in L,N′; red in N,N‴; cyan arrowheads). Boxes in K and N are shown at higher magnification in K′-K‴ and N′-N‴, respectively. Sparse bright lineage-labeled taste cells are detected at later times (I,L, arrows), and are distinguishable from dimmer Shh-tdTomato⁺ neurites (I,L, arrowheads within taste buds). Nuclei are counterstained with Draq5 (blue). B-D and F-H are images of whole tongue and ganglia. I-N‴ are compressed confocal z-stacks. Scale bars: 1 mm in B-D; 150 μm in F-H; 10 μm in I-N‴.