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PAX9 is a transcription factor deeply involved in the gene networks that regulate odontogenesis. To date, only a restricted number of mutations in this gene have been associated with non-syndromic tooth agenesis. Six families segregating non-syndromic oligodontia/hypodontia were screened for mutations in PAX9 gene. A novel missense mutation lying in the exon 2 close to the end of the paired domain in three families was identified. Heterozygous mutation C503G is expected to result in an alanine-to-glycine amino acid change in residue 168 (Ala168Gly), which is invariably conserved among several species. The alanine-glycine change might lead to protein structural alteration because of the unique flexibility properties of glycine. Three mutations in intron 2 were also detected. Variations IVS2-109G>C, IVS2-54A>G, and IVS2-41A>G were identified in both affected and unaffected members of the sample; however, these polymorphic variants may be involved in the phenotype as one proband showing all three intronic mutations in homozygosis was affected with the most severe oligodontia within the sample.

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