Ultrastructure of forming enamel in mouse bearing a transgene that disrupts the amelogenin self-assembly domains

• Published in: Calcified tissue international 2002-08, Vol.71 (2), p.155-166
• Main Authors: Dunglas, C, Septier, D, Paine, M L, Zhu, D H, Snead, M L, Goldberg, M
• Format: Article
• Language: English
• Subjects: Amelogenesis - genetics; Amelogenin; Amino Acid Sequence; Animals; Animals, Newborn; Dental Enamel - growth & development; Dental Enamel - ultrastructure; Dental Enamel Proteins - genetics; Genetic Engineering; Incisor - growth & development; Incisor - ultrastructure; Mice; Mice, Inbred C57BL; Mice, Inbred CBA; Mice, Transgenic; Microscopy, Electron; Molar - growth & development; Molar - ultrastructure; Molecular Sequence Data; Protein Structure, Tertiary - genetics; Tooth Germ - growth & development; Tooth Germ - ultrastructure
• ISSN: 0171-967X; 1432-0827
• DOI: 10.1007/s00223-001-2116-5

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.