AMELX

AMELX is a gene that provides instructions for making a protein called amelogenin. This protein is essential for the normal development of tooth enamel, which is a hard, white material that forms the protective outer layer of each tooth. The AMELX gene is located on the X chromosome.

Function

The AMELX gene provides instructions for making a protein called amelogenin. This protein is essential for the normal development of tooth enamel. Amelogenin makes up more than 90 percent of the enamel's organic (non-mineral) content. This protein plays a critical role in regulating the thickness of the enamel and promoting the growth of long, thin crystals of a mineral called hydroxyapatite. These crystals make up the hard, protective enamel.

Genetic Changes

More than 15 mutations in the AMELX gene have been identified in people with X-linked amelogenesis imperfecta, a condition that affects the structure and appearance of tooth enamel. These mutations change single protein building blocks (amino acids) in the amelogenin protein or delete a small amount of DNA from the AMELX gene. As a result, the amelogenin protein is unstable and quickly broken down, or it is missing entirely. Without enough functional amelogenin, tooth enamel is abnormally thin and soft and may have a yellow or brown color. Teeth with defective enamel are weak and easily damaged.

Inheritance

This condition is inherited in an X-linked recessive pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders much more frequently than females.

See Also

• X-linked amelogenesis imperfecta
• Tooth enamel
• Hydroxyapatite

References

• Genetics Home Reference: AMELX
• OMIM: AMELOGENIN, X-LINKED; AMELX