Objective: To study the distribution of ameloblastin (AMBN) gene polymorphism in coal-fire caused fluorosis (CFCF) in Chongqing municipality and the relationship between AMBN gene polymorphism and the susceptibility to dental fluorosis.
Methods: Under a case-control study, 100 children aged 8 - 12 and 30 adults with dental fluorosis were enrolled in Wushan and Fengjie counties of Chongqing from December 2010 to February 2011. Another 100 children aged 8 - 12 and 30 adults with non-dental fluorosis were chosen as internal control groups together with 50 children and 30 adults without dental fluorosis were selected as external control groups in the non-epidemic area of Yubei district. DNA was extracted from peripheral blood sample of these people. Genotype of AMBN gene 7 extron 538_540delGGA, 10 extron 657A > G and 13 extron 986C > T loci were detected using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique.
Results: The rates of 7 extron 538_540delGGA loci among case, internal and external control groups were as follows: GGA/GGA-/- 61.2% (74/121), 78.5% (102/130), 74.3% (52/70) ; GGA/-: 24.0% (29/121), 15.4% (20/130), 22.9% (16/70) ; -/-: 14.8% (18/121), 6.1% (8/130), 2.8% (2/70), the difference was statistically significant (χ(2) = 14.353 P < 0.05). The AA appeared to be 86.8% (105/121), 93.1% (121/130), 91.4% (64/70) and AG were 13.2% (16/121), 6.9% (9/130), 8.6% (6/70), with difference not statistically significant (χ(2) = 2.972, P > 0.05). CC appeared as 81.0% (98/121), 90.0% (117/130), 87.1% (61/70) while CT as 19.0% (23/121), 10.0% (13/130), 12.9% (9/70), with difference not statistically significant (χ(2) = 4.319, P > 0.05). In comparing with the two control groups, the frequency of GGA/GGA was decreasing (χ(2) values were 8.957, 3.405, respectively, P < 0.05) while the frequency of -/- was increasing (χ(2) values were 5.134, 6.833, respectively, P < 0.05).
Results: from the univariate analysis showed that the individuals who were carrying -/- genotype had an increased risk of suffering from fluorosis (OR values were 2.7, 5.9, respectively, P < 0.05). When compared with the internal control group, the CT genotype of case group showed an increase (χ(2) = 4.139, P < 0.05) while individuals that carrying CT genotype had an increased risk of suffering from fluorosis (OR = 2.1, P < 0.05), in epidemic-area.
Conclusion: Our results showed that the 7 extron 538_540delGGA and the 13 extron 986C > T loci polymorphism in AMBN gene might serve as the susceptibility factors causing the coal-fired fluorosis.