The amelogenin proteins are the most abundant organic components of developing dental enamel. Their importance for the proper mineralization of enamel is evident from the association between previously identified mutations in the X-chromosomal gene that encodes them and the enamel defect amelogenesis imperfecta. In this investigation, an adult male presenting with a severe hypoplastic enamel phenotype was found to have a single base deletion at the codon for amino acid 110 of the X-chromosomal 175-amino acid amelogenin protein. The proband's mother, who also has affected enamel, carries the identical deletion on one of her X-chromosomes, while the father has both normal enamel and DNA sequence. This frameshift mutation deletes part of the coding region for the repetitive portion of amelogenin as well as the hydrophilic tail, replacing them with a 47-amino acid segment containing nine cysteine residues. While greater than 60% of the protein is predicted to be intact, the severity of this phenotype illustrates the importance of the C-terminal region of the amelogenin protein for the formation of enamel with normal thickness.
Bibliographical noteFunding Information:
We are indebted to family members for their participation in this study. We thank Dr. K. Nathanson for bringing this kindred to our attention, Dr. B. Friedman for contributing photographs and radiographs, Dr. C.W. Besterman for clinical observations and Dr. E. Golub for technical discussions. The DNA sequencing was done by Mr. T. Tucker of the Biopolymer Analysis Laboratory of the University of Pennsylvania School of Dental Medicine, and through the University of Pennsylvania Sequencing Facility in the Department of Genetics and Cancer Center. This investigation was supported by NIH grants DE10149 and DE11089 (CWG), from the National Institute of Craniofacial and Dental Research.
Copyright 2008 Elsevier B.V., All rights reserved.
- Amelogenesis imperfecta
- Genetic disease