A Spontaneous Mutation: Amelogenesis Imperfecta with Cysts in Rats

Abstract

Amelogenesis imperfecta (AI) is an inherited dental disease of enamel formation in humans, and there are various phenotypes due to the combination of enamel quality and quantity. We encountered four female IGS rats with spontaneous AI including odontogenic cysts in the incisor teeth. Histopathologically, in the incisors of the rats, the enamel organ was disorganized with the remaining enamel matrix residing within the enamel space. The expanding cysts derived from the enamel organ were formed in the periosteal connective tissue on the labial side. At the bottom of the tooth germs, the precursor cells of the epithelial root sheath were arranged regularly and the enamel organs were preserved to the same degree as those of normal rats. In the molar teeth of the affected rats an enamel matrix remained on the neck and crown of the erupted teeth; however, no abnormality was observed at the tooth root. Although an animal model of AI has been developed from mutants of the SHR-SP rat strain, the present cases represent another potential model of the disease because of the differences in the way the enamel matured and the odontogenic cyst formation in the incisors.

A novel autosomal‐recessive mutation, whitish chalk‐like teeth, resembling amelogenesis imperfecta, maps to rat chromosome 14 corresponding to human 4q21

“…On the other hand, a spontaneous mutant with AI, reported by K atsuta et al . (28), was found in a colony of Sprague‐Dawley rats with a genetic background similar to wct . The morphological characteristics of K atsuta 's mutant rats closely resemble those of our wct mutants; for instance, the formation of cysts was observed on the labial side of the incisors of these rats (28).…”