Oral and maxillofacial pathology
Phenotypes and genotypes in 2 DGI families with different DSPP mutations

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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.133C⥇T) in family 1 and a missense mutation (c.52G⥇T) 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.133C⥇T and c.52G⥇T in DSPP could be the 2 mutation hotspots. The same DSPP mutations may be causative for multiple unrelated DGI families with different clinical phenotypes.

Section snippets

Pedigrees investigation and sample collection

The study protocol was approved by the Institutional Review Board of Wuhan University. Written consent was obtained from all participants before enrollment. All available family members were examined clinically and the affected individuals were given a panoramic radiograph to confirm the diagnosis of DGI-II. One intact impacted mandibular third molar was extracted from the proband in family 1 and stored in 2.5% glutaraldehyde for histological analysis. A 5-cc quantity of venous blood samples

Results

Clinical and radiographic examination was performed in 13 affected participants in family 1 and 6 affected individuals in family 2. The pedigrees are shown in Fig. 1, A, and Fig. 2, A, which were ascertained from a 30-year-old proband (III:26) in family 1 and a 5-year-old boy in family 2 (IV:2). The teeth of the proband in family 1 exhibited generalized yellow-brown discoloration and severe attrition (Fig. 1, B). The panoramic radiograph revealed obliterated pulp chambers and root canals in all

Discussion

According to the Shields’ classification, DGI-II and III are isolated inherited dentin defects and different from each other.1 DGI-III affects a population known as the Brandywine triracial isolate.15 Levin et al.16 described in detail the discrepancy between the 2 disorders. Amber deciduous teeth with severe attrition in DGI-III often showed very large pulp chambers and multiple pulp exposures; permanent teeth have pulpal spaces that are either smaller than normal or completely obliterated.

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    • Cited by (0)

    The authors would like to thank all of the patients and families who contributed to this study. This work was supported by grant No. 30271415 from the National Science Foundation of China and No. 2004BA720A24 from National Mega-Projects of Science Research for the 10th Five-Year Plan, the Ministry of Science and Technology of China.

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