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Genetics Home Reference: your guide to understanding genetic conditions
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AMELX

Reviewed February 2007

What is the official name of the AMELX gene?

The official name of this gene is “amelogenin, X-linked.”

AMELX is the gene's official symbol. The AMELX gene is also known by other names, listed below.

What is the normal function of the AMELX gene?

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 enamel, which is the hard, white material that forms the protective outer layer of each tooth. Enamel is composed mainly of mineral-containing crystals. These microscopic crystals are arranged in organized bundles that give enamel its strength and durability. Although the exact function of amelogenin is not well understood, it appears to separate and support the ribbon-like 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.

Studies suggest that small amounts of amelogenin may also be present in tissues other than developing tooth enamel. For example, amelogenin has been found in certain bone, bone marrow, and brain cells. The function of amelogenin in these tissues is unknown.

One copy of the amelogenin gene is located on each of the sex chromosomes (the X and Y chromosomes). The AMELX gene, which is located on the X chromosome, makes almost all of the body's amelogenin. The copy of the amelogenin gene on the Y chromosome, AMELY, makes very little amelogenin and is not needed for enamel formation.

How are changes in the AMELX gene related to health conditions?

amelogenesis imperfecta - caused by mutations in the AMELX gene

At least 15 mutations in the AMELX gene have been identified in people with X-linked forms of amelogenesis imperfecta. (X-linked disorders are caused by mutations in genes on the X chromosome.) Some AMELX mutations lead to the production of an abnormal version of the amelogenin protein that can interfere with the formation and organization of enamel crystals. Other AMELX mutations prevent one copy of the gene from producing any amelogenin protein at all. Enamel cannot form properly without an adequate amount of amelogenin.

Males have a single copy of the X chromosome in each cell. Males who inherit a defective copy of the AMELX gene have very little amelogenin and develop almost no enamel to cover and protect their teeth. Females have two copies of the X chromosome in each cell. Females who inherit one altered copy of the AMELX gene are less severely affected because they have a normal copy of the gene on the other X chromosome to produce amelogenin. Their tooth enamel may have structural defects such as a distinctive pattern of vertical grooves. No symptoms other than abnormal enamel development have been reported in people with AMELX mutations.

Where is the AMELX gene located?

Cytogenetic Location: Xp22.31-p22.1

Molecular Location on the X chromosome: base pairs 11,293,412 to 11,300,760

The AMELX gene is located on the short (p) arm of the X chromosome between positions 22.31 and 22.1.

The AMELX gene is located on the short (p) arm of the X chromosome between positions 22.31 and 22.1.

More precisely, the AMELX gene is located from base pair 11,293,412 to base pair 11,300,760 on the X chromosome.

See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.

Where can I find additional information about AMELX?

You and your healthcare professional may find the following resources about AMELX helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the AMELX gene or gene products?

  • AIH1
  • ALGN
  • amelogenin (amelogenesis imperfecta 1, X-linked)
  • AMELX_HUMAN
  • AMG
  • AMGL
  • AMGX

See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What glossary definitions help with understanding AMELX?

amelogenesis ; bone marrow ; cell ; chromosome ; enamel ; gene ; hypoplasia ; inherit ; mineral ; protein ; sex chromosomes

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).

References

  • Deutsch D, Haze-Filderman A, Blumenfeld A, Dafni L, Leiser Y, Shay B, Gruenbaum-Cohen Y, Rosenfeld E, Fermon E, Zimmermann B, Haegewald S, Bernimoulin JP, Taylor AL. Amelogenin, a major structural protein in mineralizing enamel, is also expressed in soft tissues: brain and cells of the hematopoietic system. Eur J Oral Sci. 2006 May;114 Suppl 1:183-9; discussion 201-2, 381. (http://www.ncbi.nlm.nih.gov/pubmed/16674683?dopt=Abstract)
  • Greene SR, Yuan ZA, Wright JT, Amjad H, Abrams WR, Buchanan JA, Trachtenberg DI, Gibson CW. A new frameshift mutation encoding a truncated amelogenin leads to X-linked amelogenesis imperfecta. Arch Oral Biol. 2002 Mar;47(3):211-7. (http://www.ncbi.nlm.nih.gov/pubmed/11839357?dopt=Abstract)
  • Hart PS, Aldred MJ, Crawford PJ, Wright NJ, Hart TC, Wright JT. Amelogenesis imperfecta phenotype-genotype correlations with two amelogenin gene mutations. Arch Oral Biol. 2002 Apr;47(4):261-5. (http://www.ncbi.nlm.nih.gov/pubmed/11922869?dopt=Abstract)
  • Kida M, Sakiyama Y, Matsuda A, Takabayashi S, Ochi H, Sekiguchi H, Minamitake S, Ariga T. A novel missense mutation (p.P52R) in amelogenin gene causing X-linked amelogenesis imperfecta. J Dent Res. 2007 Jan;86(1):69-72. (http://www.ncbi.nlm.nih.gov/pubmed/17189466?dopt=Abstract)
  • Kim JW, Simmer JP, Hu YY, Lin BP, Boyd C, Wright JT, Yamada CJ, Rayes SK, Feigal RJ, Hu JC. Amelogenin p.M1T and p.W4S mutations underlying hypoplastic X-linked amelogenesis imperfecta. J Dent Res. 2004 May;83(5):378-83. (http://www.ncbi.nlm.nih.gov/pubmed/15111628?dopt=Abstract)
  • 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. Review. (http://www.ncbi.nlm.nih.gov/pubmed/16931858?dopt=Abstract)
  • NCBI Gene (http://www.ncbi.nlm.nih.gov/gene/265)
  • Stephanopoulos G, Garefalaki ME, Lyroudia K. Genes and related proteins involved in amelogenesis imperfecta. J Dent Res. 2005 Dec;84(12):1117-26. Review. (http://www.ncbi.nlm.nih.gov/pubmed/16304440?dopt=Abstract)
  • Wright JT, Hart PS, Aldred MJ, Seow K, Crawford PJ, Hong SP, Gibson CW, Hart TC. Relationship of phenotype and genotype in X-linked amelogenesis imperfecta. Connect Tissue Res. 2003;44 Suppl 1:72-8. Review. (http://www.ncbi.nlm.nih.gov/pubmed/12952177?dopt=Abstract)
  • Wright JT. The molecular etiologies and associated phenotypes of amelogenesis imperfecta. Am J Med Genet A. 2006 Dec 1;140(23):2547-55. Review. (http://www.ncbi.nlm.nih.gov/pubmed/16838342?dopt=Abstract)

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

 
Reviewed: February 2007
Published: August 25, 2014