Dental News - New study focuses on teeth outside of the mouth

Dental Tribune International

Thu. 2. November 2017

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GENEVA, Switzerland: Researchers from the University of Geneva (UNIGE) are seeking to learn why certain species of catfish are able to grow teeth outside the mouth. These catfish are covered with bony plates bristling with thin teeth that regularly fall out and then grow back. The researchers believe their results will help in understanding the mechanisms that allow the formation and regeneration of teeth in all vertebrates, including humans.

The denticulate catfish do not have scales and many species possess an armour of bony plates coated with thin teeth, which consist of pulp, enamel and dentine. These teeth, which are capable of regeneration, play a role in defence against predators and in relationships between individual catfish and can even lengthen in males during the reproductive season. “We tried to find out how these extra-oral teeth, called odontodes, have reappeared in the course of evolution and how they develop,” said study co-author Carlos Rivera-Rivera, a doctoral student in the UNIGE Department of Genetics and Evolution.

Reconstructing the evolutionary history of catfish, researchers compared specific genes of the various denticulate families with those of other families lacking odontodes. “Odontodes appeared around 120 million years ago in the denticulate catfish lineage, long before the emergence of bony plates. The latter do not therefore constitute a prerequisite to activate the development of the teeth present on the body,” said co-author Dr Juan Montoya-Burgos, who heads a research group that is part of the Institute of Genetics and Genomics of Geneva at UNIGE.

According to the scientists, it was through the analysis of the different locations of odontodes that they were able to discover that, in species without bony plates, the teeth always develop on a bony structure, of any type, for example on an ossified fin ray. From this, they concluded that bone probably plays a key role in the induction of dental tissue.

The researchers are now trying to decipher the molecular dialogue that takes place during the formation of bone and teeth that allows the latter to develop and then regenerate. They believe that it will also be possible to identify the genes linked to the development of odontodes by comparing gene expression in the denticulate and non-denticulate species.

The results thus far were published in an article titled “Trunk dental tissue evolved independently from underlying dermal bony plates but is associated with surface bones in living odontode-bearing catfish” in the Proceedings of the Royal Society B on 25 October.