Variants on chromosome 4q21 near PKD2 and SIBLINGs are associated with dental caries

A recent genome-wide association study for dental caries nominated the chromosomal region 4q21 near ABCG2, PKD2 and the SIBLING gene family. In this investigation we followed-up and fine-mapped this region using a tag-SNP (single nucleotide polymorphism) approach in 13 age- and race-stratified samples from 6 independent studies (N=4,089). Participants were assessed for dental caries via intra-oral examination and 49 tag-SNPs were genotyped capturing much of the variation in the 4q21 locus. Linear models were used to test for genetic association, while adjusting for sex, age, and components of ancestry. SNPs in and near PKD2 showed significant evidence of association in individual samples of black adults (rs17013735, p-value=0.0009) and white adults (rs11938025; p-value=0.0005; rs2725270, p-value=0.003). Meta-analyses across black adult samples recapitulated the association with rs17013735 (p-value=0.003), which occurs at low frequency in non-African populations, possibly explaining the race-specificity of the effect. In addition to race-specific associations, we also observed evidence of gene-by-fluoride exposure interaction effects in white adults for SNP rs2725233 upstream of PKD2 (p=0.002). Our results show evidence of regional replication, though no single variant clearly accounted for the original GWAS signal. Therefore, while we interpret our results as strengthening the hypothesis that chromosome 4q21 may impact dental caries, additional work is needed.