title: Human and mouse enamel phenotypes resulting from mutation or altered expression of AMEL, ENAM, MMP20 and KLK4.
abstract: Amelogenesis imperfecta (AI) is caused by AMEL, ENAM, MMP20 and KLK4 gene mutations. Mice lacking expression of the AmelX, Enam and Mmp20 genes have been generated. These mouse models provide tools for understanding enamel formation and AI pathogenesis. This study describes the AI phenotypes and relates them to their mouse model counterparts. Human AI phenotypes were determined in a clinical population of AI families and published cases. Human and murine teeth were evaluated using light and electron microscopy. A total of 463 individuals from 54 families were evaluated and mutations in the AMEL, ENAM and KLK4 genes were identified. The majority of human mutations for genes coding enamel nonproteinase proteins (AMEL and ENAM) resulted in variable hypoplasia ranging from local pitting to a marked, generalized enamel thinning. Specific AMEL mutations were associated with abnormal mineralization and maturation defects. Amel and Enam null murine models displayed marked enamel hypoplasia and a complete loss of prism structure. Human mutations in genes coding for the enamel proteinases (MMP20 and KLK4) cause variable degrees of hypomineralization. The murine Mmp20 null mouse exhibits both hypoplastic and hypomineralized defects. The currently available Amel and Enam mouse models for AI exhibit enamel phenotypes (hypoplastic) that are generally similar to those seen in humans. Mmp20 null mice have a greater degree of hypoplasia than humans with MMP20 mutations. Mice lacking expression of the currently known genes associated with the human AI conditions provide useful models for understanding the pathogenesis of these conditions.
authors: Department of Pediatric Dentistry, University of North Carolina, Chapel Hill, NC 27599, USA. tim_wright@dentistry.unc.edu
authors: J Timothy
authors: JT
authors: Wright
authors: Thomas C
authors: TC
authors: Hart
authors: P Suzanne
authors: PS
authors: Hart
authors: Darrin
authors: D
authors: Simmons
authors: Cynthia
authors: C
authors: Suggs
authors: Bill
authors: B
authors: Daley
authors: Jim
authors: J
authors: Simmer
authors: Jan
authors: J
authors: Hu
authors: John D
authors: JD
authors: Bartlett
authors: Yong
authors: Y
authors: Li
authors: Zhi-An
authors: ZA
authors: Yuan
authors: W Kim
authors: WK
authors: Seow
authors: Carolyn W
authors: CW
authors: Gibson
mesh_terms: D053523:Amelogenin / Q000235:genetics*; D000818:Animals; D003743:Dental Enamel / Q000201:enzymology* / Q000473:pathology* / Q000648:ultrastructure; D003746:Dental Enamel Proteins / Q000235:genetics*; D003817:Dentition; D006801:Humans; D007610:Kallikreins / Q000235:genetics*; D053519:Matrix Metalloproteinase 20 / Q000235:genetics*; D051379:Mice; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D010858:Pigmentation
chemical_list: D053523:Amelogenin; D003746:Dental Enamel Proteins; C038456:tuftelin; D007610:Kallikreins; C120801:kallikrein 4; D053519:Matrix Metalloproteinase 20