Elsevier

Archives of Oral Biology

Volume 54, Issue 9, September 2009, Pages 846-850
Archives of Oral Biology

Expression patterns of the Fam83h gene during murine tooth development

https://doi.org/10.1016/j.archoralbio.2009.05.009Get rights and content

Abstract

Aim

Recently a novel gene, FAM83H, was identified by a genetic linkage study in the hypocalcified form of the amelogenesis imperfecta family with an autosomal dominant hereditary pattern. Little is known about this novel gene, and so we investigated the expression pattern of Fam83h in murine tooth development using serial sectional in situ hybridisation.

Methods and Materials

Using mandibles of ICR mouse at specific developmental stages, in situ hybridisation was performed by DIG-labeled RNA probe.

Results

Faint expression was detected in limited cells at embryonic day 14 (E14) in the molar. At the bell stage, E16, Fam83h was localised in the outer and inner enamel epithelium, as well as dental papilla. Fam83h expression begins on E15 in the developing incisor. At E18, Fam83h was expressed in the inner enamel epithelium of the apical bud, ameloblasts and odontoblasts. The expression was stronger in the presecretory stages than the secretory stages.

Conclusion

Fam83h was detected in the ameloblasts from the presecretory to the secretory stage, and also the odontoblasts layer and surrounding alveolar bone.

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.

Section snippets

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,

References (11)

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