Axis inhibition protein 2 (AXIN2) polymorphisms may be a risk factor for selective tooth agenesis

Selective tooth agenesis is the most common developmental abnormality of the human dentition. To date, this abnormality has been associated only with mutations in MSX1 and PAX9 mutations, however it has recently been suggested that mutations of axis inhibition protein 2 (AXIN2) may also contribute to this complex anomaly. The protein product of this gene is a negative regulator of the Wnt-signaling pathway. We searched for AXIN2 variants in a group of patients with tooth agenesis who did not have mutations of MSX1 and PAX9. Using multi-temperature single-stranded conformational polymorphism and sequencing analysis, we identified three novel AXIN2 gene variants: c.956+16A > G, c.1060-17C > T and c.2062C > T. We also observed that individuals carrying the c.956+16G and c.2062T alleles exhibited an increased risk of tooth agenesis. The calculated odds ratio was 2.94 (95% CI 1.104-7.816; p = 0.026; p(corr) = 0.234) and 4.01 (95% CI 1.563-10.301; p = 0.002; p(corr) = 0.018), respectively. Moreover, we found that the c.2062C > T transition may change exon splice enhancer-specific binding sites of the protein splicing regulators SC35 and SF2/ASF. This alternation may negatively affect the splicing process and cellular concentration of AXIN2 protein. Our findings suggest that AXIN2 polymorphic variants may be associated with both hypodontia and oligodontia.