FOXI3 gene may be involved in human dental cusp formation

By studying a historical skull collection of hairless and coated dogs, a team led by Dr Kornelius Kupczik of the Max Planck Institute for Evolutionary Anthropology in Leipzig and Prof. Martin S. Fischer of the Friedrich Schiller University Jena found that hairless dogs were almost completely missing their permanent dentition, specifically incisors, canines and premolars. The molars, however, were present. It was also found that the deciduous premolars and permanent molars of the hairless dogs repeatedly lacked certain lingual cusps.

On the basis of DNA sampled from the over-100-year-old dog skulls of the museum’s collection, the researchers demonstrated that these morphological findings are also associated with FOXI3 gene variation. The missing hair of these dog breeds is the result of a mutation of the forkhead box I3 gene (FOXI3), which belongs to a transcription factor gene family and is involved in tooth development, among other functions.

The molar phenotype of the hairless dogs can be found in wild forms of extant and extinct carnivores, and the molars of humans and great apes too show varying expressions of the lingual cusps. The researchers from Leipzig and Jena therefore suggested that FOXI3 may be of general importance in mammalian tooth development. “It is therefore possible that this gene may have played a role in evolutionary changes of human tooth morphology as well,” said Kupczik.

The study, titled “The dental phenotype of hairless dogs with FOXI3 haploinsufficiency”, was published online on 14 July 2017 in the Scientific Reports journal.

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