Ultrastructure of forming enamel in mouse bearing a transgene that disrupts the amelogenin self-assembly domains.
The mouse X-chromosomal amelogenin gene promoter was used to drive the expression of mutated amelogenin proteins in vivo. Two different transgenic mouse lines based on deletions to either the amino-terminal (A-domain deletions) or to the carboxyl-region (B-domain deletions) were bred. In the molars of newborn A-domain deleted transgenic mice the formation of the initial layer of aprismatic enamel was delayed. There were severe structural alterations in the enamel of incisors of newborn mice bearing the A-domain deletion which were not apparent in animals bearing the B-domain deletion. In the A-domain-deleted animals, stippled material accumulated throughout the entire thickness of the forming enamel apparently causing a disruption of the normal rod-to-inter-rod relationship. This stippled material was likened to and interpreted as being groupings of amelogenin nanospheres. In the B-domain-deleted animals the stippled material was detected only in minute defects of the forming enamel. These data suggest significant differences in nanosphere assembly properties for animals bearing either the A-domain or the B-domain-deleted transgene. The present in vivo experimental approach suggests that at early stages of enamel formation, the A-domain plays a greater role than does the B-domain in amelogenin self-assembly, and consequently in enamel architecture and structure.
Dunglas
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Laboratoire de Biologie et Physiopathologie Crânio-faciale EA 2496 Université Paris V Groupe Matrices Extracellulaires et Biominéralisations, Faculté de Chirurgie Dentaire, 1, rue Maurice Arnoux, 92120 Montrouge, France.
Septier
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Paine
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Zhu
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DH
Snead
M L
ML
Goldberg
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D000566:Amelogenesis / Q000235:genetics*; D053523:Amelogenin; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D003743:Dental Enamel / Q000254:growth & development / Q000648:ultrastructure*; D003746:Dental Enamel Proteins / Q000235:genetics*; D005818:Genetic Engineering; D007180:Incisor / Q000254:growth & development / Q000648:ultrastructure; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D008854:Microscopy, Electron; D008963:Molar / Q000254:growth & development / Q000648:ultrastructure; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary / Q000235:genetics; D014083:Tooth Germ / Q000254:growth & development / Q000648:ultrastructure*
D053523:Amelogenin; C507200:Amelx protein, mouse; D003746:Dental Enamel Proteins