Prtg knockdown induces arrest of the tooth germ development. (A) Prtg transcripts were dramatically decreased in the E10.5 mandible in a time-dependent manner in the organ culture (** p < 0.01). (B) Prtg expression in the E12.0 mandible was reduced to less than 5% of that in the E10.5 mandible (** p < 0.01). Tooth germ in the control sample or in the mandible treated with SE-S-ODN (C) developed to the cap stage on the 8th day of cultivation, while (D) an arrest of the tooth germ development was observed in samples treated with the AS-S-ODN. Immunohistochemically, Ki67-positive cells were seen in the control samples and in the mandibles treated with SE-S-ODN (E), and in samples treated with AS-S-ODN (F) on the 8th day after cultivation. (G) There were no significant differences in the cell proliferation in the objective areas among the control samples, the samples treated with AS-S-ODN and the samples treated with SE-S-ODN. Significant differences in the cell proliferation were noted between the DE and SM in the control samples and in the mandible treated with SE-S-ODN, while this was not observed among the areas in samples treated with AS-S-ODN (*p < 0.05, ** p < 0.01). The left sides of Figures 7C, D, E and F correspond to the buccal side, while the right side corresponds to the lingual side. Scale bars: C, D, E and F, 150 μm. Ut; untreated control sample, AS; samples treated with AS-S-ODN, SE; samples treated with SE-S-ODN. DE; dental epithelium, DM; dental mesenchyme, SM; surrounding mesenchyme (SM).