Chick tooth induction revisited.
Teeth have been missing from Aves for almost 100 million years. However, it is believed that the avian oral epithelium retains the molecular signaling required to induce odontogenesis, and this has been widely examined using heterospecific recombinations with mouse dental mesenchyme. It has also been argued that teeth can form from the avian oral epithelium owing to contamination of the mouse mesenchyme with mouse dental epithelial cells. To investigate the possibility of tooth formation from chick oral epithelium and the characteristics of possible chick enamel, we applied LacZ transgenic mice during heterospecific recombination and examined the further tooth formation. Transmission electron microscopy was used to identify the two tissues during development after heterospecific recombination. No mixing was detected between chick oral epithelium and mouse dental mesenchyme after 2 days, and secretory ameloblasts with Tomes' processes were observed after 1 week. Teeth were formed after 3 weeks with a single cusp pattern, possibly determined by epithelial factors, which is similar to that of the avian tooth in the late Jurassic period. These recombinant teeth were smaller than mouse molars, whereas perfect structures of both ameloblasts and enamel showed histological characteristics similar to those of mice. Together these observations consistent with previous report that odontogenesis is initially directed by species-specific mesenchymal signals interplaying with common epithelial signals.
Cai
Jinglei
J
Division in Anatomy and Developmental Biology, Department of Oral Biology, Research Center for Orofacial Hard Tissue Regeneration, College of Dentistry, Yonsei Center of Biotechnology, Yonsei University, Seoul, Korea.
Cho
Sung-Won
SW
Ishiyama
Mikio
M
Mikami
Masato
M
Hosoya
Akihiro
A
Kozawa
Yukishige
Y
Ohshima
Hayato
H
Jung
Han-Sung
HS
D000818:Animals; D002642:Chick Embryo / Q000502:physiology*; D002645:Chickens; D017931:DNA Primers; D004847:Epithelial Cells / Q000502:physiology; D051379:Mice; D008813:Mice, Inbred ICR; D008822:Mice, Transgenic; D008963:Molar / Q000196:embryology; D009055:Mouth / Q000196:embryology; D009061:Mouth Mucosa / Q000166:cytology / Q000196:embryology / Q000502:physiology* / Q000648:ultrastructure; D009805:Odontogenesis / Q000235:genetics; D011995:Recombination, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001616:beta-Galactosidase / Q000235:genetics
D017931:DNA Primers; D001616:beta-Galactosidase