Loss of FAM20A protein induces Amelogenesis Imperfecta in mice

FAM20A is a member of family of related proteins that has been named family with sequence similarity 20 (FAM20) with three members (FAM20A, FAM20B and FAM20C) in mammals. Recently, some studies have reported that patients with Amelogenesis Imperfecta caused by FAM20A mutation displayed several dental phenotypes including hypoplastic enamel, failure of tooth development and gingival hyperplasia. We have reported a transgenic mouse line with a 58-kb fragment deletion that encompasses part of the Fam20a gene and its upstream region shows growth disorder. In the present study, we aimed to clarify how the loss of Fam20a protein influenced the development of dental tissues in the Fam20a-/mouse. The light microscopic study (LM) of paraffin-embedded specimens demonstrated hypoplastic enamel and gingival hyperplasia in the Fam20a-/mice. The LM of ground sections of the mandibles containing teeth showed that there was no enamel covering the coronal dentine. Immunohistochemical study of the mandibles (paraffin-embedded specimens) indicated that Fam20a protein expressed in osteoid tissue and tooth germ of Fam20a+/+ mice, but does not expressed in Fam20a-/mice. In conclusion, this study revealed that the FAM20A protein is required for enamel formation.