title: Ameloblasts express type I collagen during amelogenesis.
abstract: Enamel and enameloid, the highly mineralized tooth-covering tissues in living vertebrates, are different in their matrix composition. Enamel, a unique product of ameloblasts, principally contains enamel matrix proteins (EMPs), while enameloid possesses collagen fibrils and probably receives contributions from both odontoblasts and ameloblasts. Here we focused on type I collagen (COL1A1) and amelogenin (AMEL) gene expression during enameloid and enamel formation throughout ontogeny in the caudate amphibian, Pleurodeles waltl. In this model, pre-metamorphic teeth possess enameloid and enamel, while post-metamorphic teeth possess enamel only. In first-generation teeth, qPCR and in situ hybridization (ISH) on sections revealed that ameloblasts weakly expressed AMEL during late-stage enameloid formation, while expression strongly increased during enamel deposition. Using ISH, we identified COL1A1 transcripts in ameloblasts and odontoblasts during enameloid formation. COL1A1 expression in ameloblasts gradually decreased and was no longer detected after metamorphosis. The transition from enameloid-rich to enamel-rich teeth could be related to a switch in ameloblast activity from COL1A1 to AMEL synthesis. P. waltl therefore appears to be an appropriate animal model for the study of the processes involved during enameloid-to-enamel transition, especially because similar events probably occurred in various lineages during vertebrate evolution.
authors.affiliation: UMR 7138-SAE, Research Group "Evolution & Development of the Skeleton", Université Pierre et Marie Curie, 7 quai St-Bernard, Case 5, 75005 Paris, France.
authors.forename: N
authors.initials: N
authors.lastname: Assaraf-Weill
authors.forename: B
authors.initials: B
authors.lastname: Gasse
authors.forename: J
authors.initials: J
authors.lastname: Silvent
authors.forename: C
authors.initials: C
authors.lastname: Bardet
authors.forename: J Y
authors.initials: JY
authors.lastname: Sire
authors.forename: T
authors.initials: T
authors.lastname: Davit-Béal
mesh_terms: D000565:Ameloblasts / Q000166:cytology / Q000378:metabolism*; D000566:Amelogenesis / Q000502:physiology*; D053523:Amelogenin / Q000032:analysis; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D024042:Collagen Type I / Q000032:analysis*; D000090602:Collagen Type I, alpha 1 Chain; D003743:Dental Enamel / Q000166:cytology / Q000378:metabolism; D003810:Dentinogenesis / Q000502:physiology; D004658:Enamel Organ / Q000033:anatomy & histology; D008675:Metamorphosis, Biological / Q000502:physiology; D046529:Microscopy, Electron, Transmission; D023421:Models, Animal; D009804:Odontoblasts / Q000166:cytology / Q000378:metabolism; D009805:Odontogenesis / Q000502:physiology; D010999:Pleurodeles; D014083:Tooth Germ / Q000033:anatomy & histology
chemical_list: D053523:Amelogenin; D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain
keywords: Pleurodeles waltl; amelogenin; amphibian; enameloid; in situ hybridization; odontogenesis