Fig. 3. Incisor growth under kidney capsules. Wild-type and mutant incisors growing under kidney capsules. (C,D) Higher magnification of wild-type (A) and mutant (B) incisors, respectively. (E-H) Translucent wild-type (E,G) and mutant (F,H) specimens. (G,H) Higher magnification of the apical region at the labial side of wild-type (E) and mutant (F) incisors, respectively. (I,J) HE staining of wild-type (I) and mutant (J) incisors. The apical regions of wild-type mouse incisors grew under the kidney capsules similar to naturally growing incisors in the mandible. The apical region is covered by alveolar bone (C, asterisk), and incisors erupt from the sockets of the bones. In the wild type, the enamel, the apical bud, the inner enamel epithelium, differentiated ameloblasts and odontoblasts are clearly recognizable at the labial side. The lingual side is root analog consisting of dentin, cementum and periodontal tissues. These features are consistent with incisors growing in the mandible. However, at the labial side of the mutant incisor, thin enamel is visible, along with enamel formation over half the developing tooth. Red arrows indicate the border between the crown and root (F,H,J). Neither the apical bud nor the dental epithelium at the surface of the dentin is recognizable. ab, apical bud; d, dentin; da, differentiated ameloblast; e, enamel; iee, inner enamel epithelium; od, odontoblasts; p, periodontal ligament. Scale bars: 2 mm in A; 1 mm in B,C; 500 µm in D,E; 300 µm in F; 100 µm in G-I; 150 µm in J.