Distribution and structure of dental enamel in incisors of Tabby mice.
OBJECTIVE
In Tabby mice, the Ta (EDA) gene is mutated. The resulting syndrome is homologous to hypohidrotic ectodermal dysplasia in humans. The Tabby phenotype is characterized by developmental defects of ectodermally derived structures. The teeth show aberrations in number, size and morphology. Dental enamel is a product of specialized epithelial cells, the ameloblasts. It was the aim of the present study to investigate the dental enamel phenotype in Tabby incisors, with emphasis on its distribution and structure.


METHODS
The incisors from five female Tabby and three female wild-type mice were sectioned and ground transversely, etched for 45s with 0.1% nitric acid, sputter-coated with gold-palladium, and observed in SEM.


RESULTS
All measured dimensions were more variable in Tabby mice, as was the outline of the enamel-dentin junction. Maxillary incisors were wider in Tabby mice, while mandibular incisors were wider in wild-type mice. No significant difference in enamel thickness was observed. The enamel on the mesial aspect tended to extend further lingually in Tabby incisors in both jaws. On the lateral aspect, this tendency was only significant in mandibular incisors. The enamel-dentin junction often lacked the mesial concavity. Instances of hypoplastic enamel were observed. The complex mouse enamel structure was generally well preserved in Tabby mice, only few instances of aberrant structure were observed.


CONCLUSIONS
It is suggested that the reciprocal expression pattern of Ta and Edar (the Ta ligand receptor gene) in outer and inner enamel epithelium, respectively, may influence the position of the enamel-cementum junction.
Risnes
Steinar
S
Department of Oral Biology, Faculty of Dentistry, University of Oslo, P.O. Box 1052 Blindern, 0316 Oslo, Norway. steinarr@odont.uio.no
Peterkova
Renata
R
Lesot
Hervé
H
D000818:Animals; D003743:Dental Enamel / Q000473:pathology*; D004476:Ectodermal Dysplasia / Q000235:genetics / Q000473:pathology*; D053331:Ectodysplasins; D053339:Edar Receptor; D005260:Female; D007180:Incisor / Q000002:abnormalities*; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D008817:Mice, Mutant Strains; D008855:Microscopy, Electron, Scanning; D023421:Models, Animal; D009154:Mutation; D053338:Receptors, Ectodysplasin; D018124:Receptors, Tumor Necrosis Factor
D053331:Ectodysplasins; C506019:Eda protein, mouse; D053339:Edar Receptor; C506009:Edar protein, mouse; D008565:Membrane Proteins; D053338:Receptors, Ectodysplasin; D018124:Receptors, Tumor Necrosis Factor