Family-Based Association Study On Caries-Related Gene Polymorphisms With Dental Caries In The Baikuyao Population

Objective: This study used family-based association analysis and case-control association analysis to investigate the relationship between caries-related genes polymerphisms and dental caries susceptibility in Guangxi Baikuyao population.Methods: Using a case-control design method,30 children with high caries(DMFT≥2)and 30 children with no caries(DMFT=0)were randomly selected from 12-year-old Baikuyao children from 15 primary schools in Lihuyao Township,Nandan County,Hechi City,Guangxi.The case nuclear families were composed of children with high caries and his parents,while the control nuclear families were composed of children with no caries and his parents.Oral examinations and family questionnaires was performed to collecte information on the status of permanent teeth,demographic characteristics,oral hygiene habits and food intake.Oral mucosal exfoliative cells were collected from buccal mucosa on both sides by using disposable sterile mucosal swabs.Sample’s DNA was extracted by using DNA extraction kit,and 36 SNPs from23 caries-related candicate genes were detected by SNPscan genotyping system to find out the genotype and allele frequencies.The association between the SNPs of Baikuyao children(or their parents)and caries status was analyzed by Chi-square test and Logistic regression.Then,transmission disequilibrium test(TDT)was performed in case nuclear families thorough FBAT 2.0.4 software to analyze the association between the SNPs and dental caries.The results of the two methods were compared to evaluate the relationship between candicate gene polymorphisms and caries susceptibility of Baikuyao population.Results:1.A total of 56 Baikuyao nuclear families(168 subjects)were recruited in this study,including 30 case nuclear famileis(30 children and 60parents)and 26 control nuclear families(26 children and 52 parents).The age of the parents was 39.6±6.5(mean±SD)years old.The mean DMFT of the parents was 2.71.22 adults(19.6%)were with high caries(DMFT≥5)and 90(80.4%)were with low caries(DMFT≤4).2.Hardy-Weinberg equilibrium test showed that all SNPs adhered to Hardy-Weinberg equilibrium(P > 0.05).The minor allele frequency(MAF)of rs4865673(ISL1)and rs11099896(RNF175)was lower than0.05,which was not included in the subsequent analysis.3.Case-control correlation analysis: Chi-square test of Baikuyao12-year-old children showed that the frequency of the C allele of rs27565(PART1)in high caries children was higher than caries-free group(P=0.007,c2=7.361,OR=3.000,95% CI: 1.340-6.719).Logistic regression analysis(model adjusted for gender,parents’ education level,frequency of tooth brushing,frequency of sugar intake,whether eat at school)showed that the C allele of PART1 rs27565(OR= 4.191,95%CI: 1.473-11.920,P=0.007),the T allele of AJAP1 rs4654438(OR=8.674,95% CI: 1.311-57.390,P=0.025)are associated with high caries risk of Baikuyao children.The T allele of GLUT2 rs1499821(OR=0.218,95% CI: 0.051-0.940,P=0.041)was negatively associated with high caries risk of Baikuyao children.4.The TDT of FBAT software showed that:1 In additive model,the C allele of GLUT2 rs1499821(Z=2.111,P=0.035),G allele of AJAP1 rs3896439(Z=2.263,P=0.024),and C allele of MPPED2 rs7121800(Z=2.200,P=0.028)were over-transmitted from heterozygos parents to the chilren with high caries;2 In the dominant model,the G allele of AJAP1 rs3896439(Z =2.064,P=0.039),T allele of LYZL2 rs399593(Z=2.066,P=0.039)and G allele of TUFT1 rs3748608(Z=2.099,P=0.046)were over-transmitted from heterozygos parents to the children with high caries;3 In the recessive model,the G allele of ACTN2 rs10925178(Z=2.060,P=0.039)and C allele of GLUT2 rs1499821(Z=2.111,P=0.035)were over-transmitted from heterozygos parents to the children with high caries.Conclusion:1.The family-based and case-control association analysis showed that GLUT2 rs1499821 polymorphism was associated with caries susceptibility,and the GLUT2 rs1499821 C allele might be a protective factor of Baikuyao minority.2.Family-based association analysis showed polymorphisms of AJAP1rs3896439,MPPED2 rs7121800,LYZL2 rs399593,TUFT1 rs10925178 and ACTN2 rs3748608 were associated with caries susceptibility,while Case-control association analysis showed C allele of PART1 rs27565 and T allele of AJAP1 rs4654438 was associated with high caries risk of Baikuyao children.There were differences between the two methods.We speculate that these differences are due to the relatively small sample size and population stratification in the case-control association analysis.Therefore,the sample size needs to be increased in the following study.