Utilising Next-Generation Sequencing to Explore the Molecular Etiology of Short Root Anomaly.

Objective: Short Root Anomaly (SRA) is a genetic dental disorder affecting tooth root development. The affected teeth have abnormally short roots and significantly reduced root to crown ratios. The aim of this study was to determine the mode of inheritance and the molecular aetiology of SRA in identified Hispanic families.

Methods: Dental history was taken from 5 Hispanic families. SRA diagnosis was based on 1:1.1 C:R ratios. Whole saliva was collected from eight SRA-affected and five unaffected family members with informed consent. DNA was extracted and processed for whole exome sequencing (WES). Gene mutations associated with SRA were confirmed by Sanger sequencing. Gene expression in dental cells was examined by qRT PCR, and protein localisation was determined by immunocytochemistry. Chromatin immunoprecipitation (ChIP) assay was used to confirm gene regulation.

Results: SRA exhibited an autosomal dominant pattern of inheritance in three of the five families examined. The other two families may represent a recessive trait or de novo mutations. WES analysis identified a rare mutation (rs138075877) in the H1C gene of the affected individuals from two of the AD SRA families exhibiting a localised SRA phenotype. We found this gene was differentially expressed in dental mesenchymal and epithelial cells. Finally, ChIP showed that H1C is directly regulated by a root master gene NFIC.

Conclusion: Our data demonstrates that a mutation in the H1C gene may have a causal role in AD SRA.