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Brief Description:

Researchers report that they have identified a network of dental genes that likely were involved in building the first tooth half a million years ago.

Transcript:

Hightower: New findings introduce a core evolutionary list of molecular pieces needed to make a tooth.

Streelman: This allows us to explore the molecular ancestry of teeth—so basically, how teeth are made in different organisms and how this may have changed over evolutionary history.

Hightower: Dr. Todd Streelman of the Georgia Institute of Technology, explains that he and his colleagues found the network of genes in a very unusual fish—Lake Malawi cichlids.

Streelman: It turns out that these fish are really interesting because they have jaws in their throat around the first, or the most ancestral population of teeth; and then they have teeth associated with the first jaws to evolve, which are very similar to the jaws on the front of your face. So they have teeth in two places and we can ask how these teeth in different populations are made.

Hightower: Teeth are extremely ancient structures that arose in early vertebrates— animals with a backbone—but interestingly predate jaws.

Streelman: We think this provides a developmental context as well as a historical context. It’s well-known that the first teeth probably occurred deep in the pharynx of jawless fishes about half a billion years ago. And what this means is that there’s a really long evolutionary history of teeth in the fossil record and in the organismal record. So by studying a bunch of different organisms and how they actually make their teeth we can try to understand what’s different and what’s common about all teeth.

Hightower: Because humans replace their dentition—or set of teeth only once, Dr. Streelmanhttp says that this discovery should provide useful information—to coax diseased teeth back to health with biology rather than the traditional hand-held drill.

Streelman: Many dental defects involve either the misshaping or the misplacement or complete loss of teeth at a certain stage. Some of the groups of organisms we studied replaced their dentition through their entire life. And so if we can understand how sets of genes are used to make replacement teeth or to make teeth of certain sizes and shapes we can better understand how to make biological implants that may function in the place of say, ceramic implants in dentistry.

Hightower: Streelman says that this study also shows the power of evolutionary models like cichlids in biomedical research. Rather than manipulating genes in a laboratory, the cichlids are nature's own experiment.

Streelman: An evolutionary model is a little bit different than maybe a laboratory model. A laboratory model, like the mouse, has been very useful in studying dentitions because you can do all sorts of experimental things. You can rearrange genetic elements, you can turn genes on and off. And an evolutionary model really takes the view that evolution has done these things to the organisms and to their genomes. So evolutionary models express natural variations and we are often interested in studying natural variations because this of course is the type of variation that humans express.

Hightower: Streelman is part of a team of developmental biologists, paleontologists, and computational biologists—all working together to uncover new approaches to dental treatment. For more information about this finding, go to www.nidcr.nih.gov. This is Dorie Hightower, National Institutes of Health, Bethesda, Maryland.