Characterization of putative secretory sites on ameloblasts of the rat incisor

Nanci, Antonio; Warshawsky, H.

doi:10.1002/aja.1001710204

Cited by 47 publications

(62 citation statements)

References 26 publications

(56 reference statements)

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“…The resulting interaction may serve to provide a vector of force which would orientate the nanospheres, and the entire proteinaceous matrix to the retracting ameloblast. This would influence crystallite orientation and fits well with the previous observations that crystallites tend to form at an approximately perpendicular orientation to the secretory surfaces of the Tomes' processes [Nanci and Warshawsky, 1984]. The TRAP segment of amelogenin contains all of the self-assembly 'A' domain (amino acid residues 1 through 42) [Paine and Snead, 1997].…”

Section: Abbreviations Used In This Papersupporting

confidence: 72%

Overexpression of TRAP in the Enamel Matrix Does Not Alter the Enamel Structural Hierarchy

Paine

Zhu²,

Luo³

et al. 2004

Cells Tissues Organs

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The secreted, full-length amelogenin is the dominant protein of the forming enamel organ. As enamel mineralization progresses, amelogenin is quickly subjected to proteolytic activity, and eliminated from the enamel environment. Mature enamel contains only traces of structural proteins, including enamelin and the sheath protein ameloblastin. In addition, a proteolytic fragment of amelogenin, known as the tyrosine-rich amelogenin peptide or TRAP, is present in low but isolatable quantities. By overexpressing TRAP during enamel development we sought to determine if such overexpression would result in structural alterations to the mature enamel. We reasoned that overexpressing a protein associated with enamel maturation, at an inappropriate developmental stage, would result in alterations to the enamel protein assembly and hence, alterations in enamel structure and morphology. As judged by transmission and scanning electron microscopy, the enamel formed by overexpressing TRAP showed little morphological differences when compared to the enamel of normal nontransgenic animals. Based on scanning electron-microscopic images, there was modest hypomineralization evident in the interrod enamel of the TRAP-overexpressing animals. However, this finding was inconsistent and inconsequential from a structural and functional perspective. From these results it appears that additional amounts of TRAP protein in the immature enamel matrix are not sufficient to alter the properties of the enamel extracellular matrix to an extent that the hierarchical structure of mature enamel is altered.

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Section: Abbreviations Used In This Papersupporting

confidence: 72%

Overexpression of TRAP in the Enamel Matrix Does Not Alter the Enamel Structural Hierarchy

Paine

Zhu²,

Luo³

et al. 2004

Cells Tissues Organs

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“…Because the majority of secretory granules that accumulate in Tomes' processes are labeled, it is likely that amelogenin and ameloblastin are co-packaged, at least in some of the granules. (Inset) Gold particles are also found in elements of the smooth tubular network (arrows; discussed in Nanci and Warshawsky 1984;Nanci et al 1993) situated in the distal portion of Tomes' process. IR, interrod enamel; rgs, rod growth site.…”

Section: Figurementioning

confidence: 99%

“…During appositional growth of the enamel layer, secretory granules in ameloblasts are characteristically routed towards two spatially distinct secretory sites, at which they release their contents constitutively to build up interrod and rod areas and, hence, bulk enamel thickness (Nanci and Warshawsky 1984). The organic phase of developing enamel in optimally fixed teeth appears morphologically homogeneous by electron microscopy.…”

mentioning

confidence: 99%

Comparative Immunochemical Analyses of the Developmental Expression and Distribution of Ameloblastin and Amelogenin in Rat Incisors

Nanci

Zalzal

Lavoie

et al. 1998

J Histochem Cytochem.

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127

155

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SUMMARYMineralized tissues are unique in using proteins to attract and organize calcium and phosphate ions into a structured mineral phase. A precise knowledge of the expression and extracellular distribution of matrix proteins is therefore very important in understanding their function. The purpose of this investigation was to obtain comparative information on the expression, intracellular and extracellular distribution, and dynamics of proteins representative of the two main classes of enamel matrix proteins. Amelogenins were visualized using an antibody and an mRNA probe prepared against the major alternatively spliced isoform in rodents, and nonamelogenins by antibodies and mRNA probes specific to one enamel protein referred to by three names: ameloblastin, amelin, and sheathlin. Qualitative and quantitative immunocytochemistry, in combination with immunoblotting and in situ hybridization, indicated a correlation between mRNA signal and sites of protein secretion for amelogenin, but not for ameloblastin, during the early presecretory and midto late maturation stages, during which mRNA signals were detected but no proteins appeared to be secreted. Extracellular amelogenin immunoreactivity was generally weak near secretory surfaces, increasing over a distance of about 1.25 m to reach a level slightly above an amount expected if the protein were being deposited evenly across the enamel layer. Immunolabeling for ameloblastin showed an inverse pattern, with relatively more gold particles near secretory surfaces and much fewer deeper into the enamel layer. Administration of brefeldin A and cycloheximide to stop protein secretion revealed that the immunoblotting pattern of amelogenin was relatively stable, whereas ameloblastin broke down rapidly into lower molecular weight fragments. The distance from the cell surface at which immunolabeling for amelogenin stabilized generally corresponded to the point at which that for ameloblastin started to show a net reduction. These data suggest a correlation between the distribution of amelogenin and ameloblastin and that intact ameloblastin has a transient role in promoting/stabilizing crystal elongation. A meloblasts , like all hard tissue-forming cells, release an intricate set of extracellular matrix proteins optimized for promoting the development of a closely associated mineral phase (reviewed in Deutsch et al.

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“…• • • Le prowngement dt T ornes est une extension cyto plasmique de la partie ap icale de l'amiloblaste sécré toire do.ns laquelle s'accumulent les granules dt sécré tion et où leur contenu est sécrété à deux sites dis tincts de sa membrane [22]. …”

Section: Matériel Et Méthodeunclassified

Les protéines de l'émail dentaire - Etude immunocytochimique de l'amélogenèse-

Nanci¹,

Smith²

1988

Med Sci (Paris)

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Characterization of putative secretory sites on ameloblasts of the rat incisor

Cited by 47 publications

References 26 publications

Overexpression of TRAP in the Enamel Matrix Does Not Alter the Enamel Structural Hierarchy

Overexpression of TRAP in the Enamel Matrix Does Not Alter the Enamel Structural Hierarchy

Comparative Immunochemical Analyses of the Developmental Expression and Distribution of Ameloblastin and Amelogenin in Rat Incisors

Les protéines de l'émail dentaire - Etude immunocytochimique de l'amélogenèse-

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