A novel nonsense mutation of PAX9 gene causes sporadic oligodontia

Hypodontia is the most commonly known developmental dental anomaly in human. The absence of teeth affects the appearance and mastication function of the patients. The study on the hypodontia related gene PAX9 was limited in its paired domain. In order to further understand the nature of this dental anomaly, we analyzed its genetic background of Chinese patients by molecular biological methods. Objectives: To find the Chinese patients' mutations of the hypodontia related gene PAX9. Methods: Genomic DNA was extracted from the peripheral blood or the desquamated cells of 19 hypodontia patients by using the TIANamp Blood DNA mini kit (TIANGEN, Beijing, China) and the Biotek DNA mini kit (Biotek, Beijing, China) according to the manufacturers' instructions. The entire coding region of the PAX9 gene (from exon1 to exon4) was amplified by polymerase chain reaction (PCR) using combinations of intron- and exon-specific primers. Sequencing results were compared by the BLAST (BLAST nucleotide) program of NCBI (http://www.ncbi.nlm.nih.gov/BLAST). Then the PAX9 genes of 100 control population were tested by Restriction Fragment Length Polymorphism (RFLP). Results: We found a novel mutation c.480C>G in PAX9 gene of a patient who had 6 primary molars and 20 permanent teeth missing congenitally. The mutation was located out of the highly conserved paired domain and the mutation gene was translated to a truncated protein. What's more, this mutation was not found in his parents and 100 controls. Conclusion: Novel mutation of PAX9 gene was found in the Chinese patient. This mutation was not simply a single nucleotide polymorphism (SNP) site and it led to abnormal translation. We presumed that this may be the cause of hypodontia of this patient and more study was needed. This work was supported by Beijing Natural Science Foundation (No. 7022022 and No. 7092112).