Phenotypes and genotypes in 2 DGI families with different DSPP mutations.

OBJECTIVE

The objective of this study was to characterize dentin ultrastructural features resulting from a nonsense mutation in DSPP gene and to define various phenotypes associated with specific DSPP mutations in families with Dentinogenesis Imperfecta type II (DGI-II).

STUDY DESIGN

Two families with DGI-II were investigated for phenotypes and genotypes. Mutation analysis was performed by amplifying DSPP exons and sequencing the products. Dentin ultrastructure associated with the specific mutation was examined with scanning electronic microscopy and transmission electronic microscopy.

RESULTS

Teeth discoloration, attrition, and obliterated pulp chambers showed in affected members of 2 families. "Shell" teeth phenotypes were also presented in deciduous teeth of family 1. A nonsense mutation (c.133CT) in family 1 and a missense mutation (c.52GT) in family 2 were identified in DSPP. Irregular dentin tubules, smooth dentinoenamel junction with an obvious gap, abnormal enamel structure, and amounts of fibril bundles around dentin tubules were manifested in the specimen from family 1 with the nonsense mutation in DSPP.

CONCLUSIONS

We reported characteristic tooth ultrastructure resulting from a nonsense mutation in DSPP gene and supported that the c.133CT and c.52GT in DSPP could be the 2 mutation hotspots. The same DSPP mutations may be causative for multiple unrelated DGI families with different clinical phenotypes.