Fig. 2.

Neuronal and epithelial Shh are the main sources of Hedgehog signal in taste bud homeostasis. (A) qPCR analysis of Shh, Indian Hedgehog (Ihh), Desert Hedgehog (Dhh), and a ubiquitous neuronal marker betaIII-tubulin (Tubb3) expression in the geniculate ganglion plotted as relative percentages to Hprt1. n = 5∼6 dissected ganglia from 3 mice were pooled into one sample; total number of mice: n = 9. (B) Genetic marking of Shh-expressing cells. Immunofluorescence labeling of GFP (mG, yellow) and neuronal marker (NeuN, magenta) in the geniculate ganglion from Shh^CreER/+;R26^mTmG mice. (C) Quantification of GFP-positive and NeuN-positive cell numbers in geniculate ganglion (n = 8∼12 ganglia from 6 adult Shh^CreER/+;R26^mTmG mice). (D) A tongue section containing a fungiform papilla receiving a bundle of mGFP-labeled nerve fiber (white arrow). Inset shows immunostaining of SHH protein (white) on a nerve bundle in tongue muscle. TRCs are denoted with red circles. (E) Immunostaining of SHH protein (white) within the fungiform papilla. (F) Marking of Shh-producing basal cells (arrowhead) and sensory projections from Shh-expressing neurons (arrow; also magnified in single-channel view) in Shh^CreER/+;R26^mTmG mice. (Scale bars, 10 μm.) Note that the mG marking of Shh-expressing cells within the taste bud is driven by the CAG promoter inserted at the R26 locus. The intensity of mG antibody staining thus is stronger than that of SHH protein in the basal cells (Fig. S3A).