Tuesday, February 21, 2006

 

Wanted: The Development of Archosaurian First-Generation Teeth in a Chicken Mutant

Current Biology, Vol 16, 371-377, 21 February 2006

Summary:

Modern birds do not have teeth. Rather, they develop a specialized keratinized structure, called the rhamphotheca, that covers the mandible, maxillae, and premaxillae. Although recombination studies have shown that the avian epidermis can respond to tooth-inductive cues from mouse or lizard oral mesenchyme and participate in tooth formation 1; 2, attempts to initiate tooth development de novo in birds have failed. Here, we describe the formation of teeth in the talpid2 chicken mutant, including the developmental processes and early molecular changes associated with the formation of teeth. Additionally, we show recapitulation of the early events seen in talpid2 after in vivo activation of β-catenin in wild-type embryos. We compare the formation of teeth in the talpid2 mutant with that in the alligator and show the formation of decidedly archosaurian (crocodilian) first-generation teeth in an avian embryo. The formation of teeth in the mutant is coupled with alterations in the specification of the oral/aboral boundary of the jaw. We propose an epigenetic model of the developmental modification of dentition in avian evolution; in this model, changes in the relative position of a lateral signaling center over competent odontogenic mesenchyme led to loss of teeth in avians while maintaining tooth developmental potential.

Related terms: Evolution

John Latter

Model of an Internal Evolutionary Mechanism
http://members.aol.com/jorolat/index.html

UPDATE: Reprints can be requested from the email addresses here

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Comments:
I emailed one of the authors (John F. Fallon) who very kindly sent me a copy of the paper! His email address is on this page.

John
 
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