Cloning of rat amelotin and localization of the protein to the basal lamina of maturation stage ameloblasts and junctional epithelium

Abstract

Formation of tooth enamel is a very complex process in which a specific set of proteins secreted by ameloblasts play a primordial role. As part of a screening procedure to identify novel proteins secreted by EO (enamel organ) cells of rat incisors, we isolated a partial cDNA fragment (EO-017) that is the homologue of the recently described mouse Amtn (amelotin) gene [Iwasaki, Bajenova, Somogyi-Ganss, Miller, Nguyen, Nourkeyhani, Gao, Wendel and Ganss (2005) J. Dent. Res. 84, 1127-1132]. Presented herein is the cloning of rat and pig full-length cDNAs with their deduced protein sequences. Detailed expression profiling by Northern-blot analysis and RT (reverse transcriptase)-PCR on rat and mouse tissues revealed highest expression in the mandible, more specifically in the maturation stage of the EO. Among all tissues tested, low expression was detected only in periodontal ligament, lung, thymus and gingiva. In silico analyses revealed that the Amtn gene is highly conserved in seven other mammals, but is absent from fish, birds and amphibians. The Amtn protein is enriched in proline, leucine, glutamine and threonine (52% of total) and contains a perfectly conserved protein kinase CK2 phosphorylation site. Transient transfection experiments in HEK-293 cells (human embryonic kidney cells) showed that secreted Amtn is post-translationally modified possibly through O-linked oligosaccharides on threonine residues. In concordance with its predominant expression site, immunofluorescence localization within the rat and mouse mandibles revealed Amtn localized to the basal lamina of maturation stage ameloblasts of incisors and unerupted molars. Intense Amtn protein expression was also detected in the internal basal lamina of junctional epithelium in molars. The peculiar and unique cellular localization of Amtn suggests a role in cell adhesion.

FAM20C Plays an Essential Role in the Formation of Murine Teeth

“…These results suggest that FAM20C may regulate amelogenesis through the mediation of AMBN. Another molecule that was remarkably down-regulated in the Fam20C-deficient ameloblasts was AMTN, a component of the basal lamina covering the enamel surface, which helps ameloblasts adhere to the enamel surface via hemidesmosomes (36). The loss of AMTN in the Fam20C-deficient ameloblasts may have impaired the laminal junction between the ameloblasts and enamel surface, thus leading to the detachment of the ameloblasts from the initially secreted enamel matrix (Fig.…”

Functions of KLK4 and MMP-20 in dental enamel formation

“…This basal lamina is in some ways unique to ameloblasts and contains novel components, such as amelotin (AMTN) and apin (ODAM) (Moffatt et al, 2006;Moffatt et al, 2008). These basal lamina proteins appear to bind tightly to the enamel surface, serve as the attachment apparatus for maturation stage ameloblasts, and possibly inhibit additional mineral deposition on tips of the enamel crystals.…”

A study of APin-protein interactions using protein microarray

“…분비기 법랑 모세포는 Tome' s 돌기를 특징으로 하며 왕성한 합성 및 분 비활동을 반영한다. 성숙기의 법랑모세포에는 주름세포끝 (ruffle ended)과 평탄세포끝 (smooth ended)이 주기적으 로 교대로 나타나면서 무기질 침착에 필요한 이온을 조성하 고 운반한다 [29][30][31][32][33] . 최근에 박 등 .…”