Chick tooth induction revisited.

Area of Science:

• Evolutionary Biology
• Developmental Biology
• Paleontology

Background:

• Aves (birds) have lacked teeth for approximately 100 million years.
• The avian oral epithelium is thought to retain the molecular signaling necessary for odontogenesis (tooth formation).
• Previous studies utilized heterospecific recombination with mouse dental mesenchyme, but contamination was a concern.

Purpose of the Study:

• To investigate tooth formation from chick oral epithelium.
• To characterize potential chick enamel.
• To determine if tooth formation results from chick oral epithelium or contamination.

Main Methods:

• Heterospecific recombination of chick oral epithelium with LacZ transgenic mouse dental mesenchyme.
• Transmission electron microscopy to analyze tissue interactions and development.
• Histological examination of formed teeth.

Main Results:

• No mixing between chick epithelium and mouse mesenchyme was observed after 2 days.
• Secretory ameloblasts with Tomes' processes appeared after 1 week.
• Recombinant teeth with a single cusp pattern formed after 3 weeks, exhibiting enamel histology similar to mice.

Conclusions:

• Chick oral epithelium can induce odontogenesis when provided with appropriate signals.
• The observed single-cusp pattern may be determined by epithelial factors, resembling ancient avian teeth.
• Mesenchymal signals appear to direct odontogenesis initially, interacting with common epithelial signals.