AbstractIntroduction. The ectopic canine (EC) is a common clinical complication of dental development appearing in 1-2% of the Western population The aetiology is controversial with opinion divided as to a genetic or environmental mechanism. This study addresses the hypothesis that genetic factors play an important role in the aetiology of ectopic maxillary canines. Elucidation of the extent of genetic factors will determine the feasibility of further molecular studies to identify putative genes responsible for ectopic eruption and aid in their identification. Molecular control of tooth eruption would reduce or eliminate the need for surgical procedures associated with buried and impacted teeth and facilitate treatment of those dentofacial anomalies where failure of tooth eruption is a feature. Methods. The study is divided into five parts: 1. A segregation analysis was carried out on 63 pedigrees where a proband was identified as affected with EC, in order to determine whether a genetic component does exist and to provide parameters for further investigation by linkage analysis. 2. Following a positive result from the segregation analysis, linkage analysis was carried out on DNA obtained from an informative, three generation family with seven affected members. 3. Whole exome sequencing was carried out on two distantly related affected members of this family, common, novel and rare variants being identified. 4. The exons and intron-exon junctions of the candidate genes were sequenced using Sanger sequencing in the family and in 18 unrelated cases of EC. 5. In situ hybridisation was carried out using the genes ANO5 and PPP1R14C. Results.
Results. The segregation analysis identified a major genetic component with autosomal dominant transmission and the likelihood of a single major locus being involved. The linkage analysis identified several regions of interest and this data was used to filter the results of the exome sequencing. The presence of variations in both PPP1R14C and ANO5 were necessary to precipitate the phenotype. Sanger sequencing of unaffected family members and of unrelated cases showed no similar variants. In situ hybridisation showed both PPP1R14C and ANO5 to be expressed in tooth and supporting tissues, leading to a supposition of digenic inheritance. Conclusion. The genes PPP1R14C and ANO5 are implicated in the aetiology of EC in a digenic inheritance pattern in this family. Further sequencing of affected families and functional studies are required as well as investigation of the methylation status of discordant monozygotic twins.
|Date of Award
|1 Jul 2013
|Fraser McDonald (Supervisor) & Chris Scerri (Supervisor)