title: Retinoic Acid Excess Impairs Amelogenesis Inducing Enamel Defects.
abstract: Abnormalities of enamel matrix proteins deposition, mineralization, or degradation during tooth development are responsible for a spectrum of either genetic diseases termedAmelogenesis imperfectaor acquired enamel defects. To assess if environmental/nutritional factors can exacerbate enamel defects, we investigated the role of the active form of vitamin A, retinoic acid (RA). Robust expression of RA-degrading enzymesCyp26b1andCyp26c1in developing murine teeth suggested RA excess would reduce tooth hard tissue mineralization, adversely affecting enamel. We employed a protocol where RA was supplied to pregnant mice as a food supplement, at a concentration estimated to result in moderate elevations in serum RA levels. This supplementation led to severe enamel defects in adult mice born from pregnant dams, with most severe alterations observed for treatments from embryonic day (E)12.5 to E16.5. We identified the enamel matrix proteinsenamelin(Enam),ameloblastin(Ambn), andodontogenic ameloblast-associated protein(Odam) as target genes affected by excess RA, exhibiting mRNA reductions of over 20-fold in lower incisors at E16.5. RA treatments also affected bone formation, reducing mineralization. Accordingly, craniofacial ossification was drastically reduced after 2 days of treatment (E14.5). Massive RNA-sequencing (RNA-seq) was performed on E14.5 and E16.5 lower incisors. Reductions inRunx2(a key transcriptional regulator of bone and enamel differentiation) and its targets were observed at E14.5 in RA-exposed embryos. RNA-seq analysis further indicated that bone growth factors, extracellular matrix, and calcium homeostasis were perturbed. Genes mutated in human AI (ENAM, AMBN, AMELX, AMTN, KLK4) were reduced in expression at E16.5. Our observations support a model in which elevated RA signaling at fetal stages affects dental cell lineages. Thereafter enamel protein production is impaired, leading to permanent enamel alterations.
authors.affiliation: Developmental Biology and Stem Cells Department, Institute of Genetics and Molecular and Cellular Biology (IGBMC)Illkirch, France; Centre National de la Recherche Scientifique, UMR 7104Illkirch, France; Institut National de la Santé et de la Recherche Médicale, U 964Illkirch, France; Université de StrasbourgIllkirch, France; Pediatrics Department, Faculty of Dentistry, Khon Kaen UniversityKhon Kaen, Thailand.
authors.forename: Supawich
authors.initials: S
authors.lastname: Morkmued
authors.affiliation: Developmental Biology and Stem Cells Department, Institute of Genetics and Molecular and Cellular Biology (IGBMC)Illkirch, France; Centre National de la Recherche Scientifique, UMR 7104Illkirch, France; Institut National de la Santé et de la Recherche Médicale, U 964Illkirch, France; Université de StrasbourgIllkirch, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Laugel-Haushalter
authors.affiliation: Université de Strasbourg, INSERM UMR_1121, Biomaterials and Bioengineering Strasbourg, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Mathieu
authors.affiliation: Developmental Biology and Stem Cells Department, Institute of Genetics and Molecular and Cellular Biology (IGBMC)Illkirch, France; Centre National de la Recherche Scientifique, UMR 7104Illkirch, France; Institut National de la Santé et de la Recherche Médicale, U 964Illkirch, France; Université de StrasbourgIllkirch, France.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Schuhbaur
authors.affiliation: Université de Strasbourg, INSERM UMR_1121, Biomaterials and Bioengineering Strasbourg, France.
authors.forename: Joseph
authors.initials: J
authors.lastname: Hemmerlé
authors.affiliation: Developmental Biology and Stem Cells Department, Institute of Genetics and Molecular and Cellular Biology (IGBMC)Illkirch, France; Centre National de la Recherche Scientifique, UMR 7104Illkirch, France; Institut National de la Santé et de la Recherche Médicale, U 964Illkirch, France; Université de StrasbourgIllkirch, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Dollé
authors.affiliation: Developmental Biology and Stem Cells Department, Institute of Genetics and Molecular and Cellular Biology (IGBMC)Illkirch, France; Centre National de la Recherche Scientifique, UMR 7104Illkirch, France; Institut National de la Santé et de la Recherche Médicale, U 964Illkirch, France; Université de StrasbourgIllkirch, France; Faculté de Chirurgie Dentaire, Université de StrasbourgStrasbourg, France; Faculté de Médecine, Fédération de Médecine Translationnelle de Strasbourg, Université de StrasbourgStrasbourg, France; Hôpitaux Universitaires de Strasbourg, Pôle de Médecine et Chirurgie Bucco-Dentaires, Centre de Référence des Manifestations Odontologiques des Maladies Rares, CRMRStrasbourg, France; Eastman Dental Institute, University College LondonLondon, UK.
authors.forename: Agnès
authors.initials: A
authors.lastname: Bloch-Zupan
authors.affiliation: Developmental Biology and Stem Cells Department, Institute of Genetics and Molecular and Cellular Biology (IGBMC)Illkirch, France; Centre National de la Recherche Scientifique, UMR 7104Illkirch, France; Institut National de la Santé et de la Recherche Médicale, U 964Illkirch, France; Université de StrasbourgIllkirch, France; Faculté de Chirurgie Dentaire, Université de StrasbourgStrasbourg, France.
authors.forename: Karen
authors.initials: K
authors.lastname: Niederreither
keywords: RNA-seq; enamel; enamelin; mouse models; retinoids; tooth