A comparison of enamelin and amelogenin expression in developing mouse molars

Amelogenin and enamelin are structural proteins in the enamel matrix of dev eloping teeth. The temporal and spatial patterns of enamelin expression in developing mouse molars have not been characterized, while controversy rema ins with respect to amelogenin expression by odontoblasts and cementoblasts . Here we report the results of in situ hybridization analyses of amelogeni n and enamelin expression in mouse molars from postnatal days 1, 2, 3, 7, 9 . 14, and 21. Amelogenin and enamelin mRNA in maxillary first molars was fi rst observed in pre-ameloblasts on the cusp slopes at day 2. The onsets of amelogenin and enamelin expression were approximately synchronous with the initial accumulation of predentin matrix. Both proteins were expressed by a meloblasts throughout the secretory, transition, and early maturation stage s. Enamelin expression terminated in maturation stage ameloblasts on day 9, while amelogenin expression is still detected in maturation stage amelobla sts on day 14. No amelogenin expression was observed in day 21 mouse molars . Amelogenin and enamelin RNA messages were restricted to ameloblasts. No e xpression was observed in pulp, bone, or along the developing root. We conc lude that amelogenin and enamelin are enamel-specific and do not directly p articipate in the Formation of dentin or cementum in developing mouse molar s.