The developing enamel matrix: nature and function

Abstract

SJ. Shore RC, Kirkham J: The developing enamel matrix: nature and function . Eur J Oral Sci 1998; 106 (supp/1 ): 282-291. Eur J Oral Sci, 1998 The hydroxyapatite crystals of mature enamel are unusually large, uniform and regularly disposed within the tissue, implying that their development is a highly controlled process. The organic matrix of developing enamel is presumed to play an important role in the modu lation of mineral deposition and growth during tooth morphogenesis but the precise functions of individual matrix proteins remain unclear. The aim of this rev iew was to survey the current knowledge of enamel matrix proteins with a view to suggesting possible functions. The organic matrix is highly heterogeneous, comprising protein derived from a number of different genes, including amelogenin, enamelin, ameloblastin (amelin/sheathlin), tuftelin, dentine sialophosphoprotein, enzymes and serum proteins such as albumin. Each of these classes appears to undergo post-secretory sequentia l degradation which contributes further towards matrix heterogeneity. Possible functions of these proteins include de novo minera l nucleation/ initiation (dentine sialophosphoproteir1, tuftelin), mineral ion binding as crystal precursors (amelogenin, enamelin), contro l of crystal growth (amelogenin, enamelin, ameloblastin), support of growing crystals (amelogenin, enamelin), determination of prismatic structure (ameloblastin) , cell signalling (tuftelin, ameloblastin), control of secretion (breakdown products) and protection of the mineral phase (amelogenin, enamelin). Failure of these mechanisms could lead to incomplete maturation of the enamel and the eruption of dysplastic tissue.

Biochemical and Immunohistochemical Characterization of the Amyloid in Canine Amyloid-Producing Odontogenic Tumor

“…50 In other species, amelogenin varies slightly in molecular mass. 8,35,44 Nascent amelogenin is spatially restricted to the newly secreted enamel and is processed relatively rapidly so that the subsurface, bulk, and inner enamel is dominated by a 20-kDa amelogenin molecule in the enamel matrix. 3,6 In the present study, the amino-acid sequence of canine APOT was closely homologous to that of both rat ameloblastin and porcine sheathlin.…”

“…49 Immunohistochemical results suggest that the protein is homogeneously distributed in the surface layer of the tissue (ie, in newly secreted enamel) where it appears as the nascent 62-kDa molecule. 47,50 Amelogenins form the bulk of the enamel matrix (90%) during the secretory stage of enamel development 35 and are initially secreted as a 25-kDa nascent protein in porcine tissues. 50 In other species, amelogenin varies slightly in molecular mass.…”

“…The list of enamel proteins in the developing tooth germ includes ameloblastin, amelogenin, sheathlin, enamelin, tuftelin, and others, with new proteins found as studies continue. 35,42 These proteins, produced by ameloblasts at different stages of development, are considered to play various roles in the modulation of mineral deposition and crystal growth during tooth morphogenesis. 35 Ameloblastin was cloned from an enamel protein in rat incisor tooth germs.…”

“…35,42 These proteins, produced by ameloblasts at different stages of development, are considered to play various roles in the modulation of mineral deposition and crystal growth during tooth morphogenesis. 35 Ameloblastin was cloned from an enamel protein in rat incisor tooth germs. 4,7,18 Sheathlin, considered to be part of the same protein as ameloblastin, was recently cloned from porcine tooth germs.…”

Amelogenin expression in long bone and cartilage cells and in bone marrow progenitor cells

“…They comprise 90% of the developing extracellular enamel matrix proteins (Termine et al, 1980) and play a major role in the biomineralization and structural organization of enamel (Robinson et al, 1998;Fincham et al, 1999). Amelogenins are hydrophobic molecules that self-assemble in vitro and in vivo into nanospheric structures, which regulate the oriented and elongated growth, shape, and size of the enamel mineral crystal (Fincham et al, 1994;Du et al, 2005).…”