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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed February 2009

What is the official name of the EXT1 gene?

The official name of this gene is “exostosin glycosyltransferase 1.”

EXT1 is the gene's official symbol. The EXT1 gene is also known by other names, listed below.

What is the normal function of the EXT1 gene?

The EXT1 gene provides instructions for producing a protein called exostosin-1. This protein is found in a cell structure called the Golgi apparatus, which modifies newly produced enzymes and other proteins. In the Golgi apparatus, exostosin-1 attaches (binds) to another protein, exostosin-2, to form a complex that modifies heparan sulfate. Heparan sulfate is a complex of sugar molecules (polysaccharide) that is added to proteins to form proteoglycans, which are proteins attached to several sugars. Heparan sulfate is involved in regulating a variety of body processes including blood clotting and the formation of blood vessels (angiogenesis). It also has a role in the spreading (metastasis) of cancer cells.

How are changes in the EXT1 gene related to health conditions?

hereditary multiple exostoses - caused by mutations in the EXT1 gene

About 200 mutations in the EXT1 gene have been identified in people with hereditary multiple exostoses type 1. Most of these mutations are known as "loss-of-function" mutations, as they prevent any functional exostosin-1 protein from being made. The loss of exostosin-1 protein function prevents it from forming a complex with the exostosin-2 protein and adding heparan sulfate to proteins. It is unclear how this impairment leads to the signs and symptoms of hereditary multiple exostoses.

Langer-Giedion syndrome - associated with the EXT1 gene

The deletion or mutation of the EXT1 gene and at least one additional gene on chromosome 8 causes Langer-Giedion syndrome. These EXT1 gene mutations cause no exostosin-1 protein to be made. A lack of functional exostosin-1 protein causes the multiple noncancerous (benign) bone tumors (exostoses) seen in people with Langer-Giedion syndrome.

People with Langer-Giedion syndrome are always missing one functional copy of the EXT1 gene in each cell; however, other neighboring genes may also be involved. The deletion or mutation of additional genes near the EXT1 gene likely contributes to the varied features of this condition.

Where is the EXT1 gene located?

Cytogenetic Location: 8q24.11

Molecular Location on chromosome 8: base pairs 117,799,363 to 118,111,819

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The EXT1 gene is located on the long (q) arm of chromosome 8 at position 24.11.

The EXT1 gene is located on the long (q) arm of chromosome 8 at position 24.11.

More precisely, the EXT1 gene is located from base pair 117,799,363 to base pair 118,111,819 on chromosome 8.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about EXT1?

You and your healthcare professional may find the following resources about EXT1 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 EXT1 gene or gene products?

  • exostoses (multiple) 1
  • exostosin 1
  • EXT
  • Glucuronosyl-N-acetylglucosaminyl-proteoglycan 4-alpha-N- acetylglucosaminyltransferase
  • N-acetylglucosaminyl-proteoglycan 4-beta-glucuronosyltransferase

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding EXT1?

angiogenesis ; benign ; blood clotting ; cancer ; cell ; chromosome ; clotting ; deletion ; exostoses ; gene ; Golgi apparatus ; heparan sulfate ; hereditary ; metastasis ; mutation ; polysaccharide ; protein ; proteoglycan ; sulfate ; syndrome

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Francannet C, Cohen-Tanugi A, Le Merrer M, Munnich A, Bonaventure J, Legeai-Mallet L. Genotype-phenotype correlation in hereditary multiple exostoses. J Med Genet. 2001 Jul;38(7):430-4. (
  • Lonie L, Porter DE, Fraser M, Cole T, Wise C, Yates L, Wakeling E, Blair E, Morava E, Monaco AP, Ragoussis J. Determination of the mutation spectrum of the EXT1/EXT2 genes in British Caucasian patients with multiple osteochondromas, and exclusion of six candidate genes in EXT negative cases. Hum Mutat. 2006 Nov;27(11):1160. (
  • Lüdecke HJ, Schmidt O, Nardmann J, von Holtum D, Meinecke P, Muenke M, Horsthemke B. Genes and chromosomal breakpoints in the Langer-Giedion syndrome region on human chromosome 8. Hum Genet. 1999 Dec;105(6):619-28. (
  • McCormick C, Duncan G, Goutsos KT, Tufaro F. The putative tumor suppressors EXT1 and EXT2 form a stable complex that accumulates in the Golgi apparatus and catalyzes the synthesis of heparan sulfate. Proc Natl Acad Sci U S A. 2000 Jan 18;97(2):668-73. (
  • NCBI Gene (
  • Wuyts W, Van Hul W, De Boulle K, Hendrickx J, Bakker E, Vanhoenacker F, Mollica F, Lüdecke HJ, Sayli BS, Pazzaglia UE, Mortier G, Hamel B, Conrad EU, Matsushita M, Raskind WH, Willems PJ. Mutations in the EXT1 and EXT2 genes in hereditary multiple exostoses. Am J Hum Genet. 1998 Feb;62(2):346-54. (


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? ( in the Handbook.

Reviewed: February 2009
Published: February 8, 2016