Rats which showed a dental mutation such as morphological abnormalities of the teeth were found in the SHR-SP rats at Daiichi Seiyaku, Co., Ltd. in 1981. Transferred to Tokushima University in 2003.
AMI rats exhibit amelogenesis imperfect due to underdevelopment of enamel-forming ameloblasts and white incisor. This phenotype is caused by an autosomal single recessive gene (ami).