Dynamic expression of nectins in enamel organs of mouse incisors

Abstract Objectives Nectins are immunoglobulin-like cell–cell adhesion molecules and are of four types, namely, nectin-1, nectin-2, nectin-3, and nectin-4. Cleft lip/palate-ectodermal dysplasia is caused by a mutation in the nectin-1 gene locus. However, nectin-1-deficient (KO) mice only show mild tooth defects. This study determined the intracellular localization of nectins in mouse mandibular incisors to identify their heterophilic interactions during amelogenesis. Methods Nectin localization was determined by performing immunohistochemical analysis with confocal microscopy. Nectin gene expression was determined by performing quantitative reverse transcription-PCR. Phenotypes of nectin-2 - KO mice were examined by performing micro-computed tomography, histological analysis, and organ culture. Results We found that mRNA levels of nectin-1 and nectin-3 genes were higher than those of nectin-2 and nectin-4 genes in mouse enamel organs. Nectin-2 and nectin-4 were strongly expressed at the apical adherens junctions of secretory-stage ameloblasts, whereas nectin-1 and nectin-3 were distributed between the basal adherens junction of maturation-stage ameloblasts and the stratum intermedium and papillary layers. Nectin-2-KO mice showed normal mandibular tooth shape, incisor surface pigmentation, and histology. Moreover, organ cultures of the tooth organs of nectin-2-KO mice proceeded normally. Conclusion These results indicate that nectins show graded and overlapping distribution in mouse incisors.