1. Headline
  1. Headline
updated 2/26/2009 2:26:59 PM ET 2009-02-26T19:26:59

Ever wonder why sharks get several rows of teeth and people only get one? Some geneticists did, and their discovery could spur work to help adults one day grow new teeth when their own wear out.

  1. More from TODAY.com
    1. Can love be blind? 'Paper bag dating' tests how much faces matter

      To test the theory that it's possible to form a love connection with someone without seeing his or her face, a U.K.-based ...

    2. 5 ways to reinvent cranberries for Thanksgiving
    3. These 14 bundled babes don't care if it's cold outside
    4. You won't believe these delicious Thanksgving sides are gluten-free
    5. Save these sites and apps for the best Cyber Monday deals

A single gene appears to be in charge, preventing additional tooth formation in species destined for a limited set. When the scientists bred mice that lacked that gene, the rodents developed extra teeth next to their first molars — backups like sharks and other non-mammals grow, University of Rochester scientists reported Thursday.

If wondering about shark teeth seems rather wonky, consider this: Tooth loss from gum disease is a major problem, here and abroad, and dentures or dental implants are far from perfect treatments. If scientists knew exactly what triggers a new tooth to grow in the first place, it's possible they could switch that early-in-life process on again during adulthood to regenerate teeth.

"It's exciting. We've got a clue what to do," said Dr. Songtao Shi of the University of Southern California School of Dentistry, who said the Rochester discovery will help his own research into how to grow a new tooth from scratch.

Also intriguing: All the mice born without this gene, called Osr2, had cleft palates severe enough to kill. So better understanding of this gene might play a role in efforts to prevent that birth defect, the Rochester team reported in the journal Science.

Teeth may not be visible until long after birth, but they start to form early in embryo development. Teeth ultimately erupt from a thickened band of tissue along the jaw line called the dental lamina, a band that forms in a top layer of the gum called the epithelium. Scientists have long thought the signals for tooth formation must lie in that tissue layer as well.

Not so, the Rochester team found: All the action takes place instead in a deeper cell layer called the mesenchyme.

Think of the Osr2 gene as a control switch, a kind of gene that turns on and off the downstream actions of other genes and proteins. In that mesenchymal tissue, the Osr2 gene works in concert with two other genes to make sure budding teeth form in the right spot, said lead researcher Dr. Rulang Jiang, a geneticist at Rochester's Center for Oral Biology.

"It's almost a self-generating propagation of the signal" that leads to one tooth after another forming all in a row, he explained.

Knocking that molecular pathway out of whack causes either missing or extra teeth to result, Jiang showed in a series of mouse experiments.

© 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Discuss:

Discussion comments

,

More on TODAY.com

  1. Samantha Okazaki / TODAY

    Can love be blind? 'Paper bag dating' tests how much faces matter

    11/24/2014 10:04:19 PM +00:00 2014-11-24T22:04:19
  1. Save these sites and apps for the best Cyber Monday deals

    Looking for the best deals on Cyber Monday? Retailers keep most of their plans super secret but savvy shoppers can still plan ahead by lining up all their links and getting their bookmarks ready.

    11/24/2014 4:07:42 PM +00:00 2014-11-24T16:07:42
  1. Maya Evoy; We Are Not Martha

    5 ways to reinvent cranberries for Thanksgiving

    11/24/2014 8:00:35 PM +00:00 2014-11-24T20:00:35
  1. Courtesy of Holly Dubour

    These 14 bundled babes don't care if it's cold outside

    11/24/2014 8:30:40 PM +00:00 2014-11-24T20:30:40
  1. Courtesy of Kristine Wach VanOrd

    22 photos that show the joy of adoption

    11/24/2014 1:30:35 PM +00:00 2014-11-24T13:30:35
  1. Rachel Currier; Rachel Gurk; Nic

    You won't believe these delicious Thanksgving sides are gluten-free

    11/24/2014 4:59:22 PM +00:00 2014-11-24T16:59:22