Genes that determine tooth shape identified

In a new paper published in Current Biology, scientists found substantial tooth differences between ethnicities, potentially due in part to a gene inherited from Neanderthals that was only found in study participants of European origin.

Co-lead author Dr Kaustubh Adhikari (UCL Genetics, Evolution & Environment and The Open University) said: "Teeth can tell us a great deal about human evolution, as well-preserved ancient teeth are particularly important to archaeologists, shedding light on milestones such as when we transitioned to cooked food and human tooth sizes began to shrink. But little is known about the genetic basis of variation within the modern human population on tooth size and shape, partly due to challenges in measuring teeth.

"We have now identified numerous genes that impact the development of our teeth, some of which are responsible for differences between ethnic groups."

The study used data from 882 volunteers in Colombia, of mixed European, Native American and African ancestry, including dental crown measurements (dimensions of the part of the tooth visible above the gums), derived from 3D scans of dental plaster casts. The researchers compared these measurements with the participants' genetic information in a genome-wide association study, using an analysis approach called multiomics that brings together numerous data sources.

The international team, led by researchers at UCL, the Open University, Fudan University (China), Aix-Marseille University (France), and National University of La Plata (Argentina), identified 18 genome regions that influence the size and shape of different groups of teeth, 17 of which had not been previously linked to tooth dimensions.

One of the novel associations was on a gene believed to be inherited from Neanderthals due to interbreeding with ancient humans. This genetic variant, which contributes to the biological pathway of tooth development, was only found in those of European descent, and carriers of the variant have thinner incisors (thickness of the incisors, the eight teeth situated at the front of the mouth, was measured from back to front). On the whole, those of European descent had smaller teeth.

The researchers also found associations with tooth dimensions on a gene, EDAR, that was already known to impact incisor shape in East Asian people, while the new study found that the gene also determined the width of all teeth.

First author Dr Qing Li (Fudan University) said: "Some of the genes that contribute to the normal variation of tooth dimensions among healthy people can also contribute to pathogenic variation, such as teeth failing to grow in or other dental health conditions. We hope that our findings could be useful medically, if people with particular dental problems could undergo genetic tests to help in diagnosis, or if some dental anomalies could be treated one day with gene therapies."

Co-lead author Professor Andrés Ruiz-Linares (UCL Genetics, Evolution & Environment, Fudan University, and Aix-Marseille University) added: "Our findings did not shed light on whether the genes that identify tooth shape were selected in evolution due to particular advantages to dental health, so it's possible that the genes may have been selected due to the influences they have in other areas, with tooth shape differences resulting as a side effect."

The authors of the study have previously found that genes inherited from Neanderthals may contribute to greater pain sensitivity, and impact the shape of our noses.