Genetic polymorphism of the salivary mucin gene MUC7 in severe caries in Japanese pediatric patients

Caries is a major oral disease whose onset and advance in a broad age group is lifestyle-related, but the genetic background of individuals is also a very important factor. Nevertheless, the relationship between caries frequency and genetic background remains unclear, especially for genetic polymorphisms of salivary proteins. The salivary mucin MG2 plays a role in facilitating the clearance of bacteria, interacts with Streptococcus mutans, which may be a caries pathogen, and can function as an antimicrobial agent. Here, we evaluated the statistical relationship of genetic polymorphisms of tandem repeats in the gene encoding MG2 (MUC7) with the frequency of pediatric severe caries in the Japanese population. Genomic DNA from lingual mucosal cells of 70 healthy and 92 caries patients was purified, and the frequency of genetic polymorphisms in MUC7 was evaluated by PCR. The results indicated that alleles of 6 (the most common allele) and 5 tandem repeats were observed in control and caries groups. Differences in the frequencies of polymorphisms were analyzed by Fisher's exact test. P-values for the frequencies of polymorphisms in MUC7 were as follows: 5-5 versus 5-6 repeats, 0.743; 5-5 versus both 5-6 and 6-6 repeats, 1.00; 5-6 versus 6-6 repeats, 0.254; 5-6 versus both 5-5 and 6-6 repeats, 0.266; 6-6 versus 5-5 repeats, 1.00; 6-6 versus both 5-5 and 5-6 repeats, 0.341. Our data suggest no significant association between genetic polymorphisms in the MUC7 gene and caries susceptibility in the Japanese pediatric population.