Dentin Sialoprotein and Dentin Phosphoprotein Overexpression during Amelogenesis

Abstract

The gene for dentin sialophosphoprotein produces a single protein that is post-translationally modified to generate two distinct extracellular proteins: dentin sialoprotein and dentin phosphoprotein. In teeth, dentin sialophosphoprotein is expressed primarily by odontoblast cells, but is also transiently expressed by presecretory ameloblasts. Because of this expression profile it appears that dentin sialophosphoprotein contributes to the early events of amelogenesis, and in particular to those events that result in the formation of the dentinoenamel junction and the adjacent "aprismatic" enamel. Using a transgenic animal approach we have extended dentin sialoprotein or dentin phosphoprotein expression throughout the developmental stages of amelogenesis. Overexpression of dentin sialoprotein results in an increased rate of enamel mineralization, however, the enamel morphology is not significantly altered. In wildtype animals, the inclusion of dentin sialoprotein in the forming aprismatic enamel may account for its increased hardness properties, when compared with bulk enamel. In contrast, the overexpression of dentin phosphoprotein creates "pitted" and "chalky" enamel of nonuniform thickness that is more prone to wear. Disruptions to the prismatic enamel structure are also a characteristic of the dentin phosphoprotein overexpressing animals. These data support the previous suggestion that dentin sialoprotein and dentin phosphoprotein have distinct functions related to tooth formation, and that the dentino-enamel junction should be viewed as a unique transition zone between enamel and the underlying dentin. These results support the notion that the dentin proteins expressed by presecretory ameloblasts contribute to the unique properties of the dentino-enamel junction.Dentin is an ectomesenchymal derived, collagen containing, calcified tissue that forms the major part of the tooth. Genetic diseases that result in abnormal dentin are classified in a subgrouping of dentinogenesis imperfecta. Dentinogenesis imperfecta type I (DI-I) 1 is always associated with one of the osteogenesis imperfectas, where mutations have been characterized in the following collagens: COL1A1, COL1A2, COL5A1, and COL2A1 (1), whereas dentinogenesis imperfecta type II (DI-II) is a disorder in dentin mineralization. Dentinogenesis imperfecta type III (DI-III) has a more extreme abnormal dental phenotype that impacts beyond dentin to the enamel and the pulps of affected teeth (2, 3).In dentin, two of the noncollagenous dentin matrix proteins are dentin siaolprotein (DSP) and dentin phosphoprotein (DPP). Both DSP and DPP are products of a single gene called dentin sialophosphoprotein (DSPP). Following transcription and translation of DSPP, the resulting product is post-translational cleaved to produce DSP and DPP that are primarily expressed in the dentin matrix (4). DPP (also known as phosphophoryn) is a highly acidic protein and is the major noncollagenous matrix component of dentin (ϳ90% of the dentin matrix is collagen) (5, 6). DSP is a glyco...

Critical role for αvβ6 integrin in enamel biomineralization

“…Ameloblasts also express bone sialoprotein that has binding sites for both hydroxyapatite and RGD-binding integrins (Ganss et al, 1999;Harris et al, 2000;Stubbs et al, 1997). Dentin sialoprotein, which also contains the RGD motif, is only transiently expressed in presecretory ameloblasts and may contribute to formation of the dentino-enamel junction rather than to enamel maturation (Bègue-Kirn et al, 1998;Paine et al, 2005).…”

Expression and processing of small integrin-binding ligand N-linked glycoproteins in mouse odontoblastic cells

“…DSPP protein is a precursor that is proteolytically processed into dentin sialoprotein (DSP) and dentin phosphoprotein (DPP) in rat teeth (36) whereas DSPP protein in porcine teeth is processed into DSP, DPP and a small segment termed dentin glycoprotein (DGP), which is located between DSP and DPP (37). Either DSP or DPP domain plays distinct biological functions during tooth development (38)(39)(40)(41)(42)(43)(44). In addition, two major fragments, 37-and 57-kDa originally from DMP1 precursor were observed in rat bone (45).…”

Adaptive Calcified Matrix Response of Dental Pulp to Bacterial Invasion Is Associated with Establishment of a Network of Glial Fibrillary Acidic Protein+/Glutamine Synthetase+ Cells

“…36 Moreover, overexpression of DSP results in an increased rate of enamel mineralization. 37 In dentinogenesis imperfecta type II mutation of dspp results in decreased mineralization of tooth structure evident as attrition of teeth.…”