Common gene regulatory circuit controls dentition development
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Posted April 15, 2009 |
A common gene regulatory circuit controls the development of all dentitions, from the first teeth in the throats of jawless fish that lived one-half billion years ago to the incisors and molars of modern vertebrates, according to an article published online in PLoS Biology.
"It's likely that every tooth made throughout the evolution of vertebrates has used this core set of genes," said Gareth Fraser, Ph.D., postdoctoral fellow at the School of Biology, Georgia Institute of Technology, Atlanta.
The first vertebrates to have teeth were a group of eellike jawless fish known as the conodonts that had teeth not in their mouths, but lining their throats. This particular group is long since extinct, but some modern fish retain teeth in the pharynx.
Dr. Fraser and colleagues studied tooth formation in a group of fish known for their rapid rate of evolution, the cichlids of Africa's Lake Malawi. The cichlids have teeth in their oral jaws, like humans, as well as deep in their throats on a pharyngeal jaw.
Darrin Hulsey, Ph.D., coauthor, first identified a surprising positive correlation in these fish between the number of teeth in the oral jaw and in the throat.
"Originally, I thought there wouldn't be a correlation due to the developmental differences and the evolutionary distinction between the two jaw regions, but it turns out there is," Dr. Fraser explained. "So fish that have fewer oral teeth also have fewer pharyngeal teeth. This shows that on some level there's a genetic control that governs the number of teeth in both regions."
The researchers investigated what this control might be by using in situ hybridization, a technique localizing gene expression in the cells during tooth development. They found that a common genetic network governs teeth in the two locations.
"So seemingly, regardless of where you grow a tooth, whether it's in the jaw or the pharynx, you use the same core set of genes to do it," said coauthor J. Todd Streelman, Ph.D. "We also think it's probable that this network is not just acting in teeth, but also in other similarly patterned structures like hair and feathers."
This study was funded by the National Science Foundation, National Institutes of Health, Alfred P. Sloan Foundation and GIT/UGA Biomedical Research Seed Grant Program.
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