Amelogenin is a major protein constituent of the developing enamel matrix. This protein is now well characterized from the data of amino acid sequences which have been shown to be at a high degree of homology between all species investigated to date. The gene structure of this protein has been demonstrated and it is confirmed that there are two amelogenin genes, one on the X-chromosome and the other on the Y-chromosome in humans. The mapping of human amelogenin gene in the p22 region on the X-chromosome and the gene on the Y-chromosome was established. It has been confirmed that several types of X-linked amelogenesis imperfecta are caused by structural defects in the amelogenin gene on the X-chromosome. The physiological importance of amelogenin in the enamel formation is suggested by the symptoms of this inherited disease in addition to inhibition experiments of amelogenin transcription and translation (Couwenhoven et al., J. Craniofac. Genet. Dev. Biol. 13:259-269, 1993; Diekwisch et al., Development 117:471-482, 1993). Recently, an attempt to synthesize recombinant mouse amelogenin by E. coli was also undertaken (Simmer et al., Calcif. Tissue Int. 54:312-319, 1994). The regulation of amelogenin expression is now under investigation (Chen et al., Dev. Dynamics 199:189-198, 1994) and the elucidation of this mechanism will contribute a great deal to the study of tooth development.