The Role of Discoidin Domain Receptor 2 in Tooth Development.

Area of Science:

• Developmental Biology
• Cell Signaling
• Oral Biology

Background:

• Collagen signaling is vital for bone and tooth development.
• Discoidin domain receptor 2 (DDR2), a collagen-activated receptor tyrosine kinase, is essential for skeletal development.
• Mutations in DDR2 cause spondylo-meta-epiphyseal dysplasia (SMED), a disorder affecting skeletal growth.

Purpose of the Study:

• To investigate the role of Discoidin domain receptor 2 (DDR2) in tooth formation and periodontal maintenance.
• To define the expression pattern of DDR2 during tooth development and in adult teeth.

Main Methods:

• Utilized Ddr2-LacZ knock-in mice to map Ddr2 expression patterns in developing and adult teeth.
• Employed Ddr2 knockout mice (Ddr2^null) to assess the functional role of DDR2 in tooth and periodontal development.
• Analyzed collagen content and periostin levels in the periodontal ligament (PDL).
• Investigated RUNX2 phosphorylation and cell differentiation in primary dental pulp and PDL cell cultures.

Main Results:

• DDR2 is expressed in the dental follicle, dental papilla, odontoblasts, and periodontal ligament (PDL).
• Ddr2^null mice exhibited disproportional tooth size, delayed root development, widened PDL space, and interradicular alveolar bone defects.
• Abnormal collagen content and increased periostin levels were observed in the PDL of Ddr2^null mice.
• Reduced RUNX2-S319-P and impaired odontoblast/osteoblast differentiation were noted in Ddr2-deficient cells.

Conclusions:

• DDR2 signaling is specifically expressed in odontoblasts and the PDL, indicating a critical role in tooth formation.
• DDR2 is essential for normal tooth root development and the maintenance of the surrounding periodontium.
• Defects in DDR2 signaling disrupt RUNX2-dependent differentiation, impacting tooth and alveolar bone development.