Odontogenic ameloblast-associated and amelotin are novel basal lamina components

Abstract

Odontogenic ameloblast-associated (ODAM) and amelotin (AMTN) are secreted by maturation stage ameloblasts and accumulate at the interface with enamel where an atypical basal lamina (BL) is present. This study aimed at determining and quantifying the ultrastructural distribution of ODAM and AMTN at the cell-tooth interface. Ultrathin sections of enamel organs from the early to mid- and late maturation stage of amelogenesis were processed for immunogold labeling with antibodies against ODAM, AMTN or with the lectins wheat germ agglutinin, Helix pomatia agglutinin (HPA) and Ricinus communis I agglutinin. Immunolabeling showed that both ODAM and AMTN localized to the BL. Quantitative analyses indicated that at the beginning of maturation there is a concentration of ODAM on the cell side of the BL while AMTN appears more concentrated on the enamel side. In the late maturation stage, such differential distribution is no longer apparent. All three lectins are bound to the BL. Competitive incubation with native lectins did not affect the binding efficiency of ODAM; however, AMTN binding was significantly reduced after incubation with HPA. In conclusion, ODAM and AMTN are bona fide components of the BL associated with maturation stage ameloblasts and they organize into different subdomains during the early maturation stage. The data also suggest that the BL is a dynamic structure that rearranges its organization as enamel maturation advances. Finally, the abrogation of AMTN antibody labeling by HPA supports the presence of O-linked sugars in the molecule and/or its close association with other O-glycosylated molecules.

Proinflammatory cytokines induce amelotin transcription in human gingival fibroblasts

“…Immunolabeling has shown that both AMTN and ODAM/APIN are localized to the basal lamina of ameloblasts. At the beginning of maturation, there ODAM/APIN is concentrated on the cell side of the basal lamina, while AMTN appears more concentrated on the enamel side (23). Our specimens of inflamed gingiva obtained by periodontal flap surgery contained the JE, whereas our specimens of noninflamed gingiva from edentulous residual ridges did not.…”

Analysis of enamel development using murine model systems: approaches and limitations

“…To determine the distribution of the proteins ODAM and AMTN in maturation stage rodent incisors, postembedding colloidal gold immunocytochemistry showed localization to the basal lamina associated with maturation stage ameloblasts and suggested that the basal lamina is dynamic during the maturation process (Dos Santos Neves et al, 2012). The effects of overexpression of AMTN in cellular morphology of ameloblasts at different stages of enamel formation were observed by TEM (Lacruz et al, 2012).…”

“…Mice are ideal for this purpose as their genetics have been well characterized and gene transfer technology is highly developed. The focus will be on genes encoding enamel proteins which have significant homology to those of humans, including secreted proteins amelogenin, ameloblastin, enamelin, proteases MMP20 (matrix metalloproteinase 20) and KLK4 (kallikrein 4) and cell-associated proteins ODAM (odontogenic ameloblast-associated protein) and AMTN (amelotin) (see Table 1 for list of abbreviations) (Hu et al, 2005; Wright et al, 2009; Holcroft and Ganss, 2011; Dos Santos Neves et al, 2012; Bartlett, 2013). …”

Maturation and beyond: proteins in the developmental continuum from enamel epithelium to junctional epithelium

“…In contrast, a single report using non-affinity-purified antibodies has shown Amtn expression in secretory stage enamel matrix of the mouse (Gao et al, 2010). The secreted AMTN protein accumulates at the interface between cells and enamel mineral and appears to be part of the specialized basal lamina-like layer that reappears at the onset of the maturation stage (Dos Santos Neves et al, 2012; Somogyi-Ganss et al, 2012). This restricted and specific localization of AMTN suggests functional roles in cell adhesion and/or surface enamel mineralization.…”

“…The onset of ODAM expression is slightly earlier (late secretory stage) than AMTN, but both proteins are localized in the basal lamina-like layer at the ameloblast-enamel interface. There appears to be a subtle difference in ODAM/AMTN localization with ODAM closer to the cell surface and AMTN closer to the enamel surface (Dos Santos Neves et al, 2012), but whether this bears any functional significance is not known. ODAM KO mice have not been described in the literature to date.…”