Figure 2.

Cilia are essential for SmoM2-induced neoplasia. (a) Schematic showing that skin epithelial cells exposed to tamoxifen (TAM) both delete Kif3a^flox and activate SmoM2^cond (red cells), whereas unexposed cells retain Kif3a^flox and do not activate SmoM2^cond (gray cells). Cilia are lost in cells from Kif3a^flox/− but not Kif3a^flox/+ mice exposed to tamoxifen. (b) H&E staining of dorsal skin biopsies, showing that removal of Kif3a (Kif3a^flox/−) blocks SmoM2-initiated tumorigenesis (arrows). (c) Immunofluorescence imaging showing that SmoM2 localizes to cilia (arrows) in neoplastic epidermal downgrowths. (d) Quantification of interfollicular epidermis thickness. Seven or eight independent Ker 14-Cre^ERT;SmoM2^cond;Kif3a^flox/+ and Ker14-Cre^ERT;SmoM2^cond;Kif3a^flox/− mice per genotype were analyzed. Four or five mice were analyzed for all other genotypes. (e) Protection against SmoM2-induced ear skin hyperplasia upon loss of Kif3a (arrow). (f) H&E staining of representative ear sections. (g) In situ staining showing that SmoM2-induced skin lesions upregulate Hh target genes Gli1 and Ptch1 (arrows). (h) Immunofluorescence imaging showing that Gli2 is upregulated in SmoM2-induced tumors that express Kif3a (stainings are representative of the mice analyzed in d and j). (i) Immunofluorescence imaging showing that Gli2 is upregulated upon expression of Myc-tagged SmoA1 in ciliated (wild type), but not unciliated (Kif3a^−/− and Ift172^−/−), transformed MEFs. (j) Cellular proliferation in skin, as assessed by Ki67 staining. Eight Ker14-Cre^ERT;SmoM2^cond;Kif3a^flox/+ and Ker14-Cre^ERT;SmoM2^cond;Kif3a^flox/− mice per genotype were analyzed, as well as four or five mice for the other genotypes. All scale bars are 50 μm except that in e (5 mm). All error bars shown, ± s.e.m.