title: Expression of ephrin-A ligands and EphA receptors in the developing mouse tooth and its supporting tissues.
abstract: Ephrins are cell-membrane-bound ligands for Eph receptor tyrosine kinases and regulate a variety of developmental processes. In order to investigate the potential roles of the ephrin-Eph system in tooth formation, we studied the cellular mRNA expression of Ephrin-A1-A5 and EphA2, EphA3, EphA4, EphA7, and EphA8 receptors during embryonic histomorphogenesis of the mouse first molar (embryonic days 11.5-18.5). Ephrin-A1, ephrin-A5, EphA2, EphA3, EphA4, and EphA7 were expressed in the tooth germ at the epithelial thickening stage, and later, ephrin-A1, ephrin-A5, EphA2, EphA4, and EphA7 showed distinct expression patterns in the enamel organ undergoing epithelial folding morphogenesis. Prior to birth, ephrin-A1, ephrin-A5, EphA2, and EphA4 transcripts were present in the cuspal area of the dental papilla including the preodontoblasts. In addition, ephrin-A1 and ephrin-A5 were seen in the forming blood vessels and alveolar bone, respectively. In contrast, ephrin-A2, ephrin-A3, and ephrin-A4 showed ubiquitous expression during odontogenesis, whereas EphA8 transcripts were not observed. During dental trigeminal axon pathfinding (embryonic days 12.5-13.5), ephrin-A2, ephrin-A4, and ephrin-A5 were evenly distributed in the trigeminal ganglion, whereas EphA7 was expressed in a subset of ganglion cells. These results suggest regulatory roles for ephrin-A/EphA signaling in the formation of the tooth organ proper and its supporting tissues.
authors.affiliation: Section of Anatomy and Cell Biology, Department of Biomedicine, University of Bergen, Jonas Lies Vei 91, 5009 Bergen, Norway.
authors.forename: Keijo
authors.initials: K
authors.lastname: Luukko
authors.forename: Sigbjørn
authors.initials: S
authors.lastname: Løes
authors.forename: Inger Hals
authors.initials: IH
authors.lastname: Kvinnsland
authors.forename: Päivi
authors.initials: P
authors.lastname: Kettunen
mesh_terms: D000818:Animals; D003743:Dental Enamel / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D036342:Ephrins / Q000096:biosynthesis* / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D008024:Ligands; D008334:Mandible / Q000196:embryology; D051379:Mice; D008963:Molar / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D009804:Odontoblasts / Q000166:cytology / Q000378:metabolism; D009805:Odontogenesis; D012333:RNA, Messenger / Q000096:biosynthesis; D036081:Receptors, Eph Family / Q000096:biosynthesis* / Q000235:genetics; D012668:Trigeminal Ganglion / Q000166:cytology / Q000196:embryology / Q000378:metabolism*
chemical_list: D036342:Ephrins; D008024:Ligands; D012333:RNA, Messenger; D036081:Receptors, Eph Family