Genetics with a bite

A Finnish child with braces

We hear a lot of about genome-wide association studies (GWAS) these days, but not so much about teeth. However, as those who’ve had to wear braces will testify, tooth abnormalities are a common occurrence and are perhaps the most common developmental anomaly in humans. Teeth largely acquire their final form at a very early age and researchers estimate that the age at which your first tooth appears is 70 per cent heritable.

So it was with much interest when in February, PLoS Genetics published the first large-scale genetic study of tooth development in young children. The results offer much for scientists to get their teeth into (sorry).

An international team of researchers, including Professor Marjo-Riitta Jarvelin and colleagues from Imperial College London, charted the date of first tooth emergence and the number of teeth at age one in over 6,000 people from two large-scale studies: the 1966 Northern Finland Birth Cohort and the Avon Longitudinal Study of Parents and Children (ALSPAC). They then conducted a genome-wide study on the subjects, looking for common genetic regions and gene variants associated with late tooth emergence or fewer teeth.

Their analysis identified five regions, several of which contain genes previously associated with tooth and other organ development. Four have also been linked to cancer.

For all regions, the variant associated with delayed tooth emergence was also linked to fewer teeth at the end of infancy, and the variant most strongly associated with both was found close to the gene KCNJ2. This has links to Pierre Robin syndrome and Andersen-Tawil syndrome, two conditions whose characteristics include missing teeth and late tooth development.

The researchers worked out that children with 8 or more of the variants had an average of 1.5 fewer teeth at the age of one, and grew their first tooth 1.1 months later than those with 3 or fewer of the variants.

Of course, the study, being the first of its kind, only explains a small proportion of the genetic influence on tooth development. But it might help us ascertain what effect genetics has on dental problems later in life, such as those requiring expensive orthodontic treatments.

• Reference: Pillas D et al. Genome-Wide Association Study Reveals Multiple Loci Associated with Primary Tooth Development during Infancy. PLoS Genet 2010;6(2): e1000856. DOI:10.1371/journal.pgen.1000856

Image credit: Kirsi Sipila and Raija Lahdesmaki from the University of Oulu