Non-Syndromic Dentinogenesis Imperfecta Caused by Mild Mutations in COL1A2

Area of Science:

• Genetics
• Oral Biology
• Biochemistry

Background:

• Hereditary dentin defects are classified as syndromic (e.g., osteogenesis imperfecta-related) or isolated.
• Mutations in Dentin Sialophosphoprotein (DSPP) cause dentinogenesis imperfecta (DGI) types II/III and dentin dysplasia (DD) type II.
• DGI type I is linked to COL1A1 and COL1A2 gene mutations, associated with osteogenesis imperfecta.

Purpose of the Study:

• To investigate the genetic basis of non-syndromic dentin defects.
• To identify novel gene mutations responsible for isolated hereditary dentin abnormalities.

Main Methods:

• Candidate gene sequencing of DSPP exons and boundaries in affected families.
• Whole-exome sequencing for families without DSPP mutations.
• Haplotype analysis to differentiate disease alleles.

Main Results:

• No DSPP mutations were found in three unrelated Korean families with isolated dentin defects.
• Heterozygous COL1A2 mutations (c.3233G>A, p.(Gly1078Asp) and c.1171G>A, p.(Gly391Ser)) were identified in these families.
• Haplotype analysis indicated distinct disease alleles in two families, suggesting a potential mutational hotspot in COL1A2.

Conclusions:

• COL1A2 mutations should be considered in the molecular genetic etiology of isolated dentin defects.
• Expanding genetic testing to include COL1A2 can improve diagnosis of hereditary dentin abnormalities.