Some people are more prone to cavities than others, even when their mouth hygiene is good. Differences in individual genetics, and the composition of the oral microbiome, or the species of microbes in the mouth, can influence these individual differences in cavity risk. Now scientists have revealed more about specific genetic changes that can influence the levels of various microbial species in the mouth microbiome, which ultimately affects the risk of cavities in some cases. The findings have been reported in Nature.
“The abundance of many bacterial species in our mouths is strongly influenced by human genetics,” noted senior study author Po-Ru Loh, associate member at the Broad Institute and associate professor of medicine at Harvard Medical School and Brigham and Women's Hospital. “We know that the microbial environment in one person's mouth is going to be quite different from another person's mouth due to many factors, but genetics is a pretty strong one.”
In this study, the researchers looked for links between genes and mout microbes in whole-genome sequencing data from saliva samples, which had been collected from over 12,500 volunteers. This genetic analysis method is usually used to focus on the human genome, but in this study it was also used to collect genetic data from the microbial species that were in the saliva sample from each person. In this way, the scientists could reveal links between certain human genes or variants in genes, and any of 439 microbial species in the oral microbiome.
This effort showed that there are 11 regions in the human genome that are associated with changes in the abundance of dozens of different species of oral bacteria.
The strongest link was found between a variant in a gene called FUT2, which has been associated with the composition of the gut microbiome in previous work, and the abundance of 58 oral microbes.
Another connection was found between a gene called AMY1, which encodes for a salivary digestive enzyme that breaks starch down into sugar, and changes in the levels of 40 species of oral bacteria. Many of those oral microbes feed on sugars and can create plaque on teeth over time. One variant in AMY1 was correlated with denture use; if this gene is more active in some people with that AMY1 variant, it may lead to an increase in the risk of tooth decay, because of how the gene affects a person’s mouth microbes.
“I hope these initial results can inspire the field to get excited about what you can learn about human genetic effects on microbiomes in general, but particularly oral microbiomes, because there seem to be such strong genetic effects,” Loh said.
Sources: Broad Institute of MIT and Harvard, Nature
