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URL of this page: https://medlineplus.gov/genetics/gene/amelx/

AMELX gene

amelogenin X-linked

Normal Function

The AMELX gene provides instructions for making a protein called amelogenin, which is essential for normal tooth development. Amelogenin is involved in the formation of tooth enamel, which is the hard, white material that forms the protective outer layer of each tooth. Enamel is composed mainly of mineral crystals. These microscopic crystals are organized in a way to give enamel strength and durability. Amelogenin acts as a scaffold to separate and support the crystals as they grow. Amelogenin is removed from the developing crystals when it is no longer needed, leaving mature enamel that contains very little protein.

The AMELX gene is located on the X chromosome. Males have a single copy of the X chromosome, and thus a single copy of the AMELX gene, in each cell. Females have two copies of the X chromosome, and thus two copies of the AMELX gene, in each cell. However, in females, the X chromosome undergoes a process called X-inactivation. Early in female embryonic development, one of the two X chromosomes is randomly and permanently inactivated in cells other than egg cells. X-inactivation ensures that females, like males, have only one active copy of the X chromosome in each body cell. Because of this, females also only have one active copy of the AMELX gene in each body cell.

Health Conditions Related to Genetic Changes

Amelogenesis imperfecta

Variants (also called mutations) in the AMELX gene have been found to cause a disorder called amelogenesis imperfecta. In people with this disorder, tooth enamel does not form properly. As a result, people with amelogenesis imperfecta have teeth that are unusually small, discolored, pitted, or grooved.

Some AMELX gene variants prevent the cell from producing enough amelogenin protein. Enamel cannot form properly without an adequate amount of amelogenin. Other AMELX gene variants lead to the production of an abnormal version of the amelogenin protein that cannot be processed normally and can interfere with the formation and organization of enamel crystals.

Males who have an altered copy of the AMELX gene produce very little functional amelogenin and develop enamel that is very thin and soft. 

Females who have one altered copy of the AMELX gene are typically less severely affected than males because they have a normal copy of the gene on the other X chromosome. However, because of X-inactivation, some cells have the X chromosome with the altered AMELX gene inactivated, and other cells have the X chromosome with the normal AMELX gene inactivated. As a result, some cells produce amelogenin, while others produce no amelogenin. This varied expression can cause individual teeth to have a distinctive pattern of alternating vertical grooves of normal enamel and weak, discolored enamel.

More About This Health Condition

Other Names for This Gene

  • AIH1
  • ALGN
  • AMELX_HUMAN
  • AMG
  • AMGL
  • AMGX

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases

References

  • Hu JC, Chan HC, Simmer SG, Seymen F, Richardson AS, Hu Y, Milkovich RN, Estrella NM, Yildirim M, Bayram M, Chen CF, Simmer JP. Amelogenesis imperfecta in two families with defined AMELX deletions in ARHGAP6. PLoS One. 2012;7(12):e52052. doi: 10.1371/journal.pone.0052052. Epub 2012 Dec 14. Citation on PubMed or Free article on PubMed Central
  • Margolis HC, Beniash E, Fowler CE. Role of macromolecular assembly of enamel matrix proteins in enamel formation. J Dent Res. 2006 Sep;85(9):775-93. doi: 10.1177/154405910608500902. Citation on PubMed
  • Sharmin N, Yuan J, Chow AK. Using computer-generated protein models to analyze mutations linked to Amelogenesis Imperfecta. PLoS One. 2025 Jun 26;20(6):e0326679. doi: 10.1371/journal.pone.0326679. eCollection 2025. Citation on PubMed
  • Smith CEL, Poulter JA, Antanaviciute A, Kirkham J, Brookes SJ, Inglehearn CF, Mighell AJ. Amelogenesis Imperfecta; Genes, Proteins, and Pathways. Front Physiol. 2017 Jun 26;8:435. doi: 10.3389/fphys.2017.00435. eCollection 2017. Citation on PubMed
  • Wang SK, Zhang H, Lin HC, Wang YL, Lin SC, Seymen F, Koruyucu M, Simmer JP, Hu JC. AMELX Mutations and Genotype-Phenotype Correlation in X-Linked Amelogenesis Imperfecta. Int J Mol Sci. 2024 Jun 1;25(11):6132. doi: 10.3390/ijms25116132. Citation on PubMed
  • Wright JT, Li Y, Suggs C, Kuehl MA, Kulkarni AB, Gibson CW. The role of amelogenin during enamel-crystallite growth and organization in vivo. Eur J Oral Sci. 2011 Dec;119 Suppl 1(Suppl 1):65-9. doi: 10.1111/j.1600-0722.2011.00883.x. Citation on PubMed or Free article on PubMed Central
  • Wright JT, Torain M, Long K, Seow K, Crawford P, Aldred MJ, Hart PS, Hart TC. Amelogenesis imperfecta: genotype-phenotype studies in 71 families. Cells Tissues Organs. 2011;194(2-4):279-83. doi: 10.1159/000324339. Epub 2011 May 19. Citation on PubMed or Free article on PubMed Central
  • Wright JT. The molecular etiologies and associated phenotypes of amelogenesis imperfecta. Am J Med Genet A. 2006 Dec 1;140(23):2547-55. doi: 10.1002/ajmg.a.31358. Citation on PubMed or Free article on PubMed Central

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.