FIGURE 9.

Smo is present in the cilia of Ptch^−/− MEFs in the absence of Shh ligand. A–B, Ptch^−/− MEFs were serum-starved for 48 h and then treated with either control medium (A) or N-Shh conditioned medium with 0.1 μm smoothened antagonist-1 (B) for 8 h. Cells were then fixed with paraformaldehyde and probed for acetylated tubulin (acTub, red) and Smo (green). Smo localizes to the cilia in the absence of Shh ligand, and this localization can be reversed by the Smo inhibitor smoothened antagonist-1. C–D, Smo^−/− MEFs were serum-starved for 48 h and then treated with either control medium (C) or 0.1 μm smoothened agonist (D) for 8 h. Cells were then fixed with paraformaldehyde and probed for acetylated tubulin (red) and Smo (green). Smo is not detectable in this cell line, even in the presence of smoothened agonist.