Figure 2.

Histological analysis (hematoxylin and eosin staining) of the lower incisor ameloblasts. Normal ameloblast development starts at the cervical loop region of the incisor and involves differentiation in consecutive secretory, transition, maturation, and postmaturation stages toward the incisal edge. These regions are illustrated both in central and lateral zones of the incisor in latent transforming growth factor beta binding protein (Ltbp3‐/‐) mutants (right‐side panels) and respective wild‐type (WT) controls (left‐side panels). The central (A, E, I, M) and lateral (B, F, J, N) zones of WT mice show virtually identical morphology. (A‐H) Ameloblasts of Ltbp3‐/‐ mice show no obvious changes at the secretory and transition stages. However, the papillae underlying the ameloblasts have an irregular organization, with an increased space between each papilla. (I–L) At the maturation stage, the ameloblasts of Ltbp3‐/‐ mice differentiate as shorter columnar cells (K). Ameloblasts appear highly abnormal in the lateral zone (L). (M–P) At the postmaturation stage, the ameloblast layer is disorganized in the mutants (O, P), with cell disruptions localizing mainly to the lateral zone, including the detachment of enamel (circled in P).