Despite the early identification of AMBN cleavage products in developing enamel (Fukae & Tanabe, 1987a, 1987b; Shimizu, 1984), the cloning and characterization of Ambn cDNA from multiple organisms, the early recognition of AMBN as a major constituent of developing enamel (Fincham et al., 1999), its association with dramatic enamel defects in Ambn mutant mice (Fukumoto et al., 2004), and linkage of AMBN to a chromosomal region associated with human enamel defects (MacDougall et al., 1997), only two AMBN mutations have been found to cause amelogenesis imperfecta (AI). Here, AMBN is linked to amelogenesis imperfecta.