Dental enamel: genes define biomechanics

Abstract

Regulated gene expression assembles an extracellular proteinaceous matrix to control biomineralization and the resultant biomechanical function of tooth enamel. The importance of the dominant enamel matrix protein, amelogenin (Amel); a minor transiently expressed protein, dentin sialoprotein (Dsp); an electrogenic sodium bicarbonate cotransporter (NBCe1); the timely removal of the proteinaceous matrix by a serine protease, Kallikrein-4 (Klk4); and the late-stage expression of Amelotin (Amtn) on enamel biomechanical function were demonstrated and measured using mouse models.

FIGURE 1

The hierarchy of tooth formation from genes to functioning teeth

FIGURE 2

Gene expression through enamel and dentin formation. Schematic of proteins secreted into the dentin matrix by odontoblasts and the enamel matrix by ameloblasts at the various stages of formation. With the exception of collagen, odontoblasts, and ameloblasts, expression profiles for the secreted proteins is very similar in the very early secretory stages. During the secretory stages both odontoblasts and ameloblasts gene expression profiles are entirely distinct as the enamel matures, amelotin, and kallikrein-4 are upregulated.

FIGURE 3

Enamel formation. From left to right: A layer of columnar ameloblasts lay down their protein matrix, which becomes mineralized to form enamel. Each individual ameloblast produces a cylindrical matrix field that becomes mineralized as a rod within a “honeycomb”-like continuum of interrod; the complex migratory vectors of ameloblasts weave rods into a complex fibrous network. Each rod is composed of multitudes of individual crystallites organized by amelogenin nanospheres; amelogenin proteins spontaneously form nanospheres in physologic conditions.