Human teeth evolved from the same genes that make the bizarre beaked teeth of the pufferfish, according to a new research published today which may help explain tooth loss in humans. The study, led by Gareth Fraser from the University of Sheffield's Department of Animal and Plant Sciences, found that the pufferfish had a remarkably similar tooth-making programme to other vertebrates, including humans. Publishedin the journal PNAS, the research done by an international team of scientists found that all vertebrates have some form of dental regeneration potential. However, the pufferfish use the same stem cells for tooth regeneration as humans do but only replace some teeth with elongated bands that form their characteristic beak. The study's authors, which include researchers from the Natural History Museum London and the University of Tokyo, believe the research can now be used to address questions of tooth loss in humans. "Our study questioned how pufferfish make a beak and now we've discovered the stem cells responsible and the genes that govern this process of continuous regeneration. These are also involved in general vertebrate tooth regeneration, including in humans," Fraser said. "The fact that all vertebrates regenerate their teeth in the same way with a set of conserved stem cells means that we can use these studies in more obscure fishes to provide clues to how we can address questions of tooth loss in humans," he said. The unique pufferfish beak is one of the most extraordinary forms of evolutionary novelty. This bizarre structure has evolved through the modification of dental replacement. The beak is composed of four elongated "tooth bands" which are replaced again and again. However, instead of losing teeth when they are replaced, the pufferfish fuses multiple generations of teeth together, which gives rise to the beak, enabling them to crush incredibly hard prey. "We are interested in the developmental origin of the pufferfish beak as it presents a special opportunity to understand how evolutionary novelty can arise in vertebrates more generally," said Alex Thiery, a PhD student at the University of Sheffield who contributed to the study. "Vertebrates are extraordinarily diverse, however this doesn't mean that they are dissimilar in the way in which they develop.
Our work on the pufferfish beak demonstrates the dramatic effect that small changes in development can have," Thiery said. Meanwhile, in another study published in the journal EvoDevo, Fraser and his team from the Sheffield university have also found that shark skin teeth (tooth-like scales called denticles) have the same developmental origins as reptile scales, bird feathers and human hair. Previous studies said human hair, reptile scales and bird feathers evolved from a single ancestor - a reptile that lived 300 million years ago, but this new study found that the skin teeth found on sharks also developed from the same genes. "Our study suggests the same genes are instrumental in the early development of all skin appendages from feathers and hair to shark skin teeth. Even though the final structures are very different this paper reveals that the developmental origins of all these structures are similar," Fraser said.
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