title: Chick tooth induction revisited.
abstract: 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.
authors.affiliation: 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.
authors.forename: Jinglei
authors.initials: J
authors.lastname: Cai
authors.forename: Sung-Won
authors.initials: SW
authors.lastname: Cho
authors.forename: Mikio
authors.initials: M
authors.lastname: Ishiyama
authors.forename: Masato
authors.initials: M
authors.lastname: Mikami
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hosoya
authors.forename: Yukishige
authors.initials: Y
authors.lastname: Kozawa
authors.forename: Hayato
authors.initials: H
authors.lastname: Ohshima
authors.forename: Han-Sung
authors.initials: HS
authors.lastname: Jung
mesh_terms: 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
chemical_list: D017931:DNA Primers; D001616:beta-Galactosidase