Biologists Find Gene Network That Gave Rise To First Tooth

Malawi cichlids exhibit toothed oral and pharyngeal jaw. (Credit: From: An Ancient Gene Network Is Co-opted for Teeth on Old and New Jaws Fraser GJ, Hulsey CD, Bloomquist RF, Uyesugi K, Manley NR, et al. PLoS Biology Vol. 7, No. 2, e31 doi:10.1371/journal.pbio.1000031)

From Science Daily:

ScienceDaily (Feb. 10, 2009) — A new paper in PLoS Biology reports that a common gene regulatory circuit controls the development of all dentitions, from the first teeth in the throats of jawless fishes that lived half a billion years ago, to the incisors and molars of modern vertebrates, including you and me.

"It's likely that every tooth made throughout the evolution of vertebrates has used this core set of genes," said Gareth Fraser, postdoctoral fellow at Georgia Tech's School of Biology.

The first vertebrates to have teeth were a group of eel-like jawless fish known as the conodonts that had teeth not in their mouth, but lining the throat. This particular group is long since extinct, but some modern fish retain teeth in the throat (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 both in their oral jaws, like humans, and deep in their throats on a pharyngeal jaw. A co-author of the paper, Darrin Hulsey, first identified a surprising positive correlation between the number of teeth in the oral jaw and in the throat in these fish.

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