Virulence Gene Mutation Assay In Dentinogenesis Imperfecta Type Ⅱ

By the Shields classification, inherited dentin defects are divided into 5 types: 3 types of dentinogenesis imperfecta (DGI), and 2 types of dentin dysplasia (DD). DGI-I, this is the dental phenotype in persons afflicted with OI. DGI-II, this is also named as Hereditary Opalescent Dentin. DGI-III, this was first found in the Brandywine tri-racial isolate from southern Maryland and Washington, DC. DD-I, the clinical crowns of both permanent and deciduous teeth are of normal in most cases, but radiological shows abnormal. DD-II, deciduous teeth were similar to DGI-II and permanent teeth look normal, X-ray shows abnormal.So far, all studies indicated that the DGI-II is due to a mutation occurred in DSPP gene. However, different families had different mutations and also could not find mutations in some families. In order to find mutations in this new found DGI-II family, we sequenced DSPP promoter and non-coding highly repetitive sequence in this facility. 1 Dentinogenesis imperfecta type II family sample collection and access to genomeIn order to screen the potential mutation in DGI-II kindred and to find more candidate genes, we identified and examined one family from Hubei Province of China. This family is 96 members spanning five generations. There are 12 patients in the family. No bony defect is in these kindred. More than seventy members of four-generation kindred consented to participate in this study and contributed samples for genomic DNA analyzes. The teeth show marked discoloration and attrition in both the deciduous and permanent dentitions. Pulpal obliteration occurs soon after eruption or prior to tooth eruption.2 Mutation screening of DGI-II candidate genesWith the development of study, DGI-II is now thought to be related with the mutation in DSPP Gene. There are many different mutations in DSPP gene of different kindred. In order to study the location of pathogenic gene in Dentinogenesis Imperfecta Type II, we analyzed the mutation of DSPP promoter and the coding region.Result:(1)There was no mutation found in Dentin sialophosphoprotein promoter region and non-coding region of highly repetitive sequence in this dentinogenesis imperfecta type II family.(2)Three single nucleotide polymorphisms (SNPs) were found in DSP coding sequence. Two were samesense SNPs and one was missense SNP. There are two SNPs in Exon 4, c.847 A/G(p.243N/D , rs3750025) and c.1017G/A(rs2736982,p.299S). One SNP in Exon 5, c.1447T/C(p.443G). Because of the specific feature of the highly repetitive sequence in Exon 5, this region can't be directly sequencing. The following is the possible future research directions: TOPO cloning method may be used in sequencing Exon 5; Sequencing other candidate genes after doing linkage analysis of this family.