Expression patterns of the Fam83h gene during murine tooth development
Introduction
Dental hard tissues, including enamel, dentin, and cementum, are formed by a series of interactions between oral ectoderm and ectomesenchyme.1 Tooth enamel is the most highly mineralised tissue in the human body. Mature enamel has a very low protein concentration (less than 1%) with an extremely well organised structure.2 To achieve such unique characteristics, tooth enamel is formed by an orchestration of many genes.3 Once the enamel matrix structural proteins such as amelogenin, enamelin, and ameloblastin are secreted, enamel proteinases (MMP20 and KLK4) cleave those proteins in a timely manner and impose unique properties to the cleaved protein products. During maturation, protein components should be further digested and removed from the mineralised enamel matrix.4
Amelogenesis imperfecta (AI), a hereditary enamel defect, is a complex group with genetic and phenotypic diversities. Phenotypically, AI is categorised by hypoplastic, hypocalcified, and hypomatured forms.5 Due to the matrix-mediated calcification of tooth enamel, genes encoding matrix proteins are believed to be the genes responsible for AI.4 Genetic studies have identified disease-causing mutations in most matrix-protein encoding genes except ameloblastin.6, 7 Recently, a novel gene, FAM83H, has been identified as a cause of hypocalcified enamel and is believed to encode a non-secreted protein due to the absence of a signal peptide.8, 9FAM83H is critical for proper tooth enamel calcification and is shown to be expressed in the human dental follicle and pulp tissue by RT-PCR, but the precise gene expression patterns of mRNA during tooth development are unknown. In this study, we cloned a fragment of a murine Fam83h gene and analyzed mRNA expression patterns during tooth development by in situ hybridisation.
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Animals
Adult ICR mice were housed in a temperature-controlled room (22 °C) under artificial illumination (lights on from 05:00 to 17:00) at a relative humidity of 55% with access to food and water ad libitum. The embryos were obtained from time-mated pregnant mice. Embryonic day 0 (E0) was designated as the day on which a vaginal plug was confirmed. Embryos at each developmental stage (daily intervals from E14 to PN14) were used in this study.
In situ hybridisation
For in situ hybridisation, mandibles of each stage were
Expression patterns of Fam83h mRNA during mouse incisor development
Fam83h was precisely localised using sectional in situ hybridisation at embryonic (E) days E14, E15, E16, E18, and postnatal (PN) days PN4, PN8 and PN14 (Fig. 1), since these developmental stages show the most dramatic alterations in incisor morphogenesis. At E14, Fam83h was not detected in the incisor (Fig. 1A). At E15, Fam83h was localised in the apical forming regions of the developing incisor (Fig. 1B) and in the epithelium and the surrounding mesenchyme of the incisor. At E16, Fam83h was
Discussion
It is believed that there are many genes involved in normal enamel formation as indicated by genetic and clinical heterogeneity of AI.7 Biochemical studies have characterised enamel matrix proteins. Enamel matrix proteins can be grouped as structural enamel matrix proteins (Amelogenin, Enamelin and Ameloblastin) and enamel matrix proteinases (MMP20 and KLK4). Mutational analyses have revealed AI-causing genes in these genes except ameloblastin.6 However, mouse lacking ameloblastin expression
Conclusion
The expressions of Fam83h in developing mouse teeth are now characterised in detail. Fam83h was detected in the ameloblasts from the presecretory to the secretory stage and the odontoblasts layer as well as developing alveolar bone. These data suggest that Fam83h may play important roles during ameloblast differentiation and enamel matrix calcification.
Acknowledgments
This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MEST) (No. R01-2008-000-10174-0(2008)) and by the Korea Research Foundation Grant funded by the Korean Government (KRF-2008-313-E00597).
Funding: The Korea Science and Engineering Foundation (No. R01-2008-000-10174-0(2008)) and the Korea Research Foundation (KRF-2008-313-E00597).
Competing interests: None declared.
Ethical approval: By Institute of laboratory animal resources,
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Cited by (21)
Decreased osteogenic activity and mineralization of alveolar bone cells from a patient with amelogenesis imperfecta and FAM83H 1261G>T mutation
2019, Genes and DiseasesCitation Excerpt :Inhibition of mineralization, down-regulation of the expression of osteogenic factors, and disorganization of keratin cytoskeleton and desmosome in ameloblast cells have been proposed as the pathogenic mechanisms of ADHCAI. In oral cavity, FAM83H expression was observed in the ameloblasts, odontoblasts, and alveolar bone.9 Murine ameloblast cell line transfected with Fam83h mutant cDNA (c.1186C > T) exhibited a significant decrease in expression of osteogenic marker genes, namely Runx2, Alp, and Ocn, corresponding with the reduction of ALP activity.10
Potential function of TGF-β isoforms in maturation-stage ameloblasts
2019, Journal of Oral BiosciencesP38/JNK signaling pathway mediates the fluoride-induced down-regulation of Fam83h
2016, Biochemical and Biophysical Research CommunicationsCitation Excerpt :The molecular mechanism for FAM83H in enamel formation remains largely unknown. Some studies proposed that FAM83H might be a non-secretory protein and involve in the differentiation of pre-ameloblast into fully functional ameloblast and enamel matrix calcification [23]. Understanding the regulation of fluoride on Fam83h would assist our overall knowledge of amelogenesis, as well as dental fluorosis.
Effects of Fam83h overexpression on enamel and dentine formation
2013, Archives of Oral BiologyCitation Excerpt :Its function in dental enamel formation is unknown. FAM83H expression is not tooth-specific, although it is expressed in developing teeth.13 There are 50 human FAM83H expressed sequence tags (ESTs) for normal tissues (which does not include developing teeth) listed in the NCBI database (Hs.67776).
Mutations in the Beta Propeller WDR72 Cause Autosomal-Recessive Hypomaturation Amelogenesis Imperfecta
2009, American Journal of Human GeneticsCitation Excerpt :FAM83H mutations are the only known cause of autosomal-dominant hypocalcified AI and appear relatively common.31–34 FAM83H is a cellular protein of unknown function expressed during presecretory and secretory ameloblast stages.35 Its recent discovery has confirmed that processes not taking place in the extracellular enamel matrix are also critical to amelogenesis.