Recent observations on enamel crystal formation during mammalian amelogenesis

Aoba, Takaaki

doi:10.1002/(sici)1097-0185(199606)245:2<208::aid-ar8>3.0.co;2-s

Cited by 72 publications

(61 citation statements)

References 65 publications

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“…Another important characteristic of biological apatites is their non-stoichiometry, often referred to as calcium deficiency, although it appears more complex. Even if it has been the subject of much controversy, the use of non-stoichiometric carbonated apatite as a model for the biological calcification of vertebrate hard tissues is accepted nowadays, with some alterations taking into account the multiplicity of carbonate sites in apatites related to coupled substitutions and interactions [15,[17][18][19][20].…”

Section: Structure and Chemical Formulasmentioning

confidence: 99%

“…During its formation enamel mineral is subject to several changes [18,[135][136][137]. As already mentioned, little is known of the composition of the first ribbon-like, very elongated crystals.…”

Section: Enamelmentioning

confidence: 99%

“…This process is similar to that observed for synthetic biomimetic apatites in carbonate poor solutions (Figure 2). In fact, the amount of bicarbonate ions in enamel fluid is very low (about 10 mM) [18] compared to that of bone fluid and blood (27 mM) [45]. It has been shown that the ribbon-like crystals first deposited grow in width and thickness by alternate accretion and maturation of mineral deposits modulated by ameloblast activity, alternating characteristic ruffle-ended and smooth-ended morphologies.…”

Section: Enamelmentioning

confidence: 99%

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Apatite Biominerals

2016

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Calcium phosphate apatites offer outstanding biological adaptability that can be attributed to their specific physico-chemical and structural properties. The aim of this review is to summarize and discuss the specific characteristics of calcium phosphate apatite biominerals in vertebrate hard tissues (bone, dentine and enamel). Firstly, the structural, elemental and chemical compositions of apatite biominerals will be summarized, followed by the presentation of the actual conception of the fine structure of synthetic and biological apatites, which is essentially based on the existence of a hydrated layer at the surface of the nanocrystals. The conditions of the formation of these biominerals and the hypothesis of the existence of apatite precursors will be discussed. Then, we will examine the evolution of apatite biominerals, especially during bone and enamel aging and also focus on the adaptability of apatite biominerals to the biological function of their related hard tissues. Finally, the diagenetic evolution of apatite fossils will be analyzed.

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Section: Structure and Chemical Formulasmentioning

confidence: 99%

Section: Enamelmentioning

confidence: 99%

Section: Enamelmentioning

confidence: 99%

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Apatite Biominerals

2016

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“…Various protein domains of the amelogenin have been predicted to be involved in various functions in enamel formation, such as controlling the mineralization process through interactions with the hydroxyapatite crystals (Aoba et al 1989;Fincham et al 1991;Deutsch et al 1995;Aoba, 1996;Paine et al 2000Paine et al , 2003a. Hoang et al (2002) have shown that recombinant amelogenin is responsible for cell-adhesive activity.…”

Section: Introductionmentioning

confidence: 99%

Molecular Evolution of Amelogenin in Mammals

2005

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Abstract. An evolutionary analysis of mammalian amelogenin, the major protein of forming enamel, was conducted by comparison of 26 sequences (including 14 new ones) representative of the main mammalian lineages. Amelogenin shows highly conserved residues in the hydrophilic N-and C-terminal regions. The central hydrophobic region (most of exon 6) is more variable, but it has conserved a high amount of proline and glutamine located in triplets, PXQ, indicating that these residues play an important role. This region evolves more rapidly, and is less constrained, than the other well-conserved regions, which are subjected to strong constraints. The comparison of the substitution rates in relation to the CpG richness confirmed that the highly conserved regions are subjected to strong selective pressures. The amino acids located at important sites and the residues known to lead to amelogenesis imperfecta when substituted were present in all sequences examined. Evolutionary analysis of the variable region of exon 6 points to a particular zone, rich in either amino acid insertion or deletion. We consider this region a hot spot of mutation for the mammalian amelogenin. In this region, numerous triplet repeats (PXQ) have been inserted recently and independently in five lineages, while most of the hydrophobic exon 6 region probably had its origin in several rounds of triplet insertions, early in vertebrate evolution. The putative ancestral DNA sequence of the mammalian amelogenin was calculated using a maximum likelihood approach. The putative ancestral protein was composed of 177 residues. It already contained all important amino acid positions known to date, its hydrophobic variable region was rich in proline and glutamine, and it contained triplet repeats PXQ as in the modern sequences.

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“…Developmental and calcification processes, or mineralization progresses, of tooth enamel and dentin were studied for human tooth [10][11][12] and animals 1,[13][14][15][16] . Generally, the calcification of enamel forms three sub-stages; first, a secondary mineralization increase appears from the surface toward the deeper layer; then, a tertiary mineralization increase takes place from the deeper layer toward the surface; and finally, the narrow subsurface layer mineralizes heavily and attains the highest degree of mineralization of all layers 1) .…”

Section: Discussionmentioning

confidence: 99%