Extracellular matrix proteins of dentine

Area of Science:

• Biochemistry
• Cell Biology
• Developmental Biology

Background:

• Bone and dentine share extracellular matrix proteins like type I collagen.
• Non-collagenous proteins regulate mineralization, with dentine possessing unique proteins: dentine phosphophoryn (DPP), dentine matrix protein 1 (DMP1), and dentine sialoprotein (DSP).
• DPP and DMP1 are acidic phosphoproteins potentially controlling mineralization initiation and crystal growth.

Purpose of the Study:

• To investigate the nature, biosynthesis, localization, and gene structure of dentine sialoprotein (DSP).
• To understand the expression patterns of DSP during tooth development.

Main Methods:

• Immunolocalization studies using rat tissues.
• cDNA sequencing to determine DSP protein structure.
• Northern blot analysis to detect DSP mRNA.
• In situ hybridization in rat and mouse teeth.

Main Results:

• DSP is a 53 kDa sialic acid-rich glycoprotein synthesized by young and mature odontoblasts, dental pulp cells, and pre-ameloblasts.
• DSP cDNA reveals a 366-residue protein with potential glycosylation and phosphorylation sites, dissimilar to known proteins.
• DSP mRNA exhibits alternative splicing and potentially arises from two genes.
• DSP mRNA is expressed in young odontoblasts and pre-ameloblasts, with expression ceasing upon maturation to secretory ameloblasts.

Conclusions:

• DSP is synthesized by specific cell types during tooth development, primarily odontoblasts and pre-ameloblasts.
• The transient expression of DSP in pre-ameloblasts suggests a role in epithelial-mesenchymal interactions during tooth formation.
• DSP's unique characteristics and expression pattern highlight its specialized function in dentine formation.