Amelotin expression during amelogenesis in the salamander
A-D: larval stages 34, 35, 36 and 38, respectively ; E-K: three year-old specimens. Transverse (A-D, E, J) and longitudinal (F-I, K) sections of demineralized jaws. A-D, F-J: in situ hybridization; E: histology; K: negative control. A: Enamel deposition on top of enameloid. The ameloblasts surrounding the enameloid cap express AMTN. B: Enamel maturation. Ameloblasts are strongly labelled along the crown base where enamel was recently deposited while labelling is weaker at its top where enamel is well mineralized. C: Late maturation stage. AMTN is no longer detected in the ameloblasts around the crown, but is identified in the cells at the surface of the dentin shaft, in a region lacking enamel. D: Tooth undergoing attachment process. Along the tooth base AMTN is still expressed in the cells of the inner dental epithelium. E: Differentiated tooth showing polarized ameloblasts. F: Early deposition of enamel matrix. AMTN transcripts are not detected, while thin layers of enamel and predentin matrix are observed. G: Enamel matrix deposition. AMTN mRNAs are clearly identified in the ameloblasts around the tooth top. H: Early enamel maturation. A strong AMTN expression is observed in the ameloblasts both facing the mineralized enamel and the recently deposited enamel matrix along the tooth shaft. I: Late enamel maturation. The ameloblasts are no longer labelled at the top of the tooth, where enamel is mature (empty space after demineralization), but are labelled in the cells facing the tooth matrix along the tooth shaft. J: Tooth in process of attachment. AMTN expression is visible in the inner dental epithelium cells facing the tooth matrix along the tooth base. am: ameloblasts; de: dentin; es: demineralized enamel space; od: odontoblasts; ode: outer dental epithelium. Scale bars: A-D = 25 μm; E-K = 50 μm.