Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists report gene network in early tooth development

11.02.2009
Darwin had his finches, Morgan had his fruit flies, and scientists today have cichlid fishes to trace the biological origins of jaws and teeth. In this week's issue of the journal PLoS Biology, researchers supported by the National Institute of Dental and Craniofacial Research, part of the National Institutes of Health, report they have deduced a network of dental genes in cichlids that likely was present to build the first tooth some half a billion years ago.

The researchers say their finding lays out a core evolutionary list of molecules needed to make a tooth. These original dental genes, like a four-cylinder Model T engine to the marvels of modern automotive engineering, were then gradually replaced, rewired, or left in place to produce the various shapes and sizes of teeth now found in nature, from shark to mouse to monkey to human.

Todd Streelman, Ph.D., a scientist at Georgia Institute of Technology in Atlanta and senior author on the study, said the discovery should provide useful information for researchers attempting to coax diseased teeth back to health with biology rather than the traditional hand-held drill. "To truly understand any part of the body, you must know how it was originally designed," said Streelman. "This is especially important when it comes to teeth. The teeth of fishes not only develop distinct sizes and shapes, they are also repaired, shed, and replaced throughout life."

"But these characteristics, once intertwined, have been decoupled through the ages in higher organisms, and the ability to repair and regrow teeth has been largely lost," he added. "If we could learn to selectively restore these traits in the dentist's office, it would mark a major step forward in helping people protect and repair their teeth. I think this gene network provides a nice evolutionary clue on how best to proceed."

Teeth are extremely ancient structures that arose in early vertebrates - animals with a backbone - but interestingly predate jaws. The fossil record indicates the first patterned set of teeth, or dentition, arose in the back of the pharynx of jawless fish. The pharynx is a tube-like part of the throat that functioned in early fish as a rudimentary jaw in which pharyngeal teeth filtered and processed food.

Over the millennia, as vertebrates developed more powerful opposing jaws for feeding in water and on land, most species adapted their dentitions there. Today, scientists can offer a real-life glimpse of this developmental bifurcation by pointing to vertebrates, such as zebrafish, that retain pharyngeal teeth only; others, such as mouse and human, that have oral teeth only; and a subset, including cichlids, that thrives with both.

That's where the cichlids enter the research picture. In Lake Malawi, one of East Africa's Great Lakes, scientists can find a great diversity of dentitions among more than 1,000 cichlid species. Most species are endemic to East Africa and closely related, but they have evolved into a rainbow of colors, shapes, and sizes over the last one to two million years to enable them to inhabit the lake's diverse terrain.

"They really are quite unique," said Gareth Fraser, a postdoctoral fellow in the Streelman laboratory and lead author on the paper. "Some cichlids have in total more than 3,000 teeth lining their pharynx and mouth. Each tooth gets replaced every 50 to 100 days with each tooth position maintaining its own stem cell niche, or environment, that initiates development of the next generation of teeth."

Last year, Fraser and colleagues described a gene network that seemed to control the patterning of tooth size, number, and spacing in Lake Malawi cichlids. Interestingly, the genes began this patterning very early in embryonic development. This indicated to the scientists that teeth are patterned similarly to other ectodermally-derived organs, such as feathers and hairs. The ectoderm is one of three germ layers, or groups of cells, that form the external covering of a developing embryo.

They then asked a follow-up question: Is tooth number controlled similarly in the pharyngeal and oral jaw? As straightforward as the question seemed, it made no obvious biological sense. The two jaws are developmentally decoupled, as separate and distinct spatially in the embryo as Africa and North America. What's more, the oral jaw is a relative evolutionary newcomer that is thought to have originated from the loss of a particular set of genes during the transition from jawless to jawed vertebrates.

As described in their current PLoS Biology paper, co-author Darrin Hulsey, Ph.D., now at the University of Tennessee, found tooth number was indeed correlated in the two jaws. This surprising finding then raised the all-important question of how this was developmentally possible.

The scientists hypothesized that their previously described gene network might hold the key. The term "network" is used here to connote multiple genes that broadly synchronize their expression during a phase of development, not in the systems biology sense of nodes of direct temporal interaction.

Their hunch turned out to be correct. "We found that even though these two jaws are evolutionarily and developmentally distinct, they share a network of genes that pattern and limit tooth number," said Fraser. "What's really interesting is this network includes genes that are known to be involved in the patterning of hairs, feathers, and other ectodermally-derived tissues. This tells us that the network is quite ancient and fundamentally important to creating a dentition; otherwise, it would have been lost in time between the evolution of the two jaws."

"Our work also shows the power of evolutionary models like cichlids in biomedical research," added Streelman. "You don't need to artificially turn genes on or off under controlled laboratory conditions to see what might happen. The cichlids are nature's own experiment, and they open up exciting biological opportunities that you just can't glean as possibilities from traditional model organisms."

Bob Kuska | EurekAlert!
Further information:
http://www.nidcr.nih.gov
http://www.nih.gov

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

DGIST develops 20 times faster biosensor

24.04.2017 | Physics and Astronomy

Nanoimprinted hyperlens array: Paving the way for practical super-resolution imaging

24.04.2017 | Materials Sciences

Atomic-level motion may drive bacteria's ability to evade immune system defenses

24.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>