CROCLIST: Mutant Chickens w/Archosaurian Teeth

[Steve Grenard]

http://dsc.discovery.com/news/briefs...icken_ani.html

Mutant Chickens Grow Teeth
By Jennifer Viegas, Discovery News


Feb. 22, 2006 — Chickens born with a mutated gene associated with tooth
development were coaxed by researchers into growing functioning teeth,
according to a paper published in this week's Current Biology.

Researchers previously caused teeth to grow in birds by combining mouse
tooth-forming tissue with bird jaw tissue, but this time the scientists
merely enhanced a genetic trait that exists naturally in the mutant birds.

The unusual feat represents the first evidence for tooth development in
birds without grafts or tissue manipulation.

Lead author Matthew Harris told Discovery News that the early theropod
dinosaur ancestors of birds possessed impressive choppers.

(Below: Original Reference from Med-Line)


Quote:
The development of archosaurian first-generation teeth in a chicken mutant.

* Harris MP,
* Hasso SM,
* Ferguson MW,
* Fallon JF.

Department of Anatomy, University of Wisconsin, 1300 University Avenue,
Madison, Wisconsin 53706, USA. matthew.harris at tuebingen.mpg.de

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, 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 beta-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.