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


Reviewed September 2008

What is the official name of the HEXA gene?

The official name of this gene is “hexosaminidase subunit alpha.”

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

What is the normal function of the HEXA gene?

The HEXA gene provides instructions for making one part (subunit) of an enzyme called beta-hexosaminidase A. Specifically, the protein produced from the HEXA gene forms the alpha subunit of this enzyme. One alpha subunit joins with one beta subunit (produced from the HEXB gene) to form a functioning enzyme.

Beta-hexosaminidase A plays a critical role in the brain and spinal cord (central nervous system). This enzyme is found in lysosomes, which are structures in cells that break down toxic substances and act as recycling centers. Within lysosomes, beta-hexosaminidase A forms part of a complex that breaks down a fatty substance called GM2 ganglioside.

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

Tay-Sachs disease - caused by mutations in the HEXA gene

More than 120 mutations that cause Tay-Sachs disease have been identified in the HEXA gene. These mutations reduce or eliminate the activity of the enzyme beta-hexosaminidase A, which prevents the enzyme from breaking down GM2 ganglioside. As a result, this substance builds up to toxic levels, particularly in nerve cells in the brain and spinal cord. Progressive damage caused by the buildup of GM2 ganglioside leads to the destruction of these cells, which causes the signs and symptoms of Tay-Sachs disease.

Most of the known HEXA mutations result in a completely nonfunctional version of beta-hexosaminidase A. These mutations cause the severe form of Tay-Sachs disease, which appears in infancy. Other mutations reduce but do not eliminate the activity of beta-hexosaminidase A; these genetic changes are responsible for the less severe forms of Tay-Sachs disease, which appear later in life.

Where is the HEXA gene located?

Cytogenetic Location: 15q24.1

Molecular Location on chromosome 15: base pairs 72,343,437 to 72,376,179

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

The HEXA gene is located on the long (q) arm of chromosome 15 at position 24.1.

The HEXA gene is located on the long (q) arm of chromosome 15 at position 24.1.

More precisely, the HEXA gene is located from base pair 72,343,437 to base pair 72,376,179 on chromosome 15.

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

Where can I find additional information about HEXA?

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

  • Beta-hexosaminidase A
  • beta-N-Acetylhexosaminidase A
  • Hex A
  • hexosaminidase A (alpha polypeptide)
  • N-acetyl-beta-glucosaminidase

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

What glossary definitions help with understanding HEXA?

central nervous system ; enzyme ; gene ; nervous system ; protein ; subunit ; toxic

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


  • Chavany C, Jendoubi M. Biology and potential strategies for the treatment of GM2 gangliosidoses. Mol Med Today. 1998 Apr;4(4):158-65. Review. (
  • Gene Review: Hexosaminidase A Deficiency (
  • Lemieux MJ, Mark BL, Cherney MM, Withers SG, Mahuran DJ, James MN. Crystallographic structure of human beta-hexosaminidase A: interpretation of Tay-Sachs mutations and loss of GM2 ganglioside hydrolysis. J Mol Biol. 2006 Jun 16;359(4):913-29. Epub 2006 Apr 27. (
  • Mahuran DJ. Biochemical consequences of mutations causing the GM2 gangliosidoses. Biochim Biophys Acta. 1999 Oct 8;1455(2-3):105-38. Review. (
  • Matsuzawa F, Aikawa S, Sakuraba H, Lan HT, Tanaka A, Ohno K, Sugimoto Y, Ninomiya H, Doi H. Structural basis of the GM2 gangliosidosis B variant. J Hum Genet. 2003;48(11):582-9. Epub 2003 Oct 24. (
  • Montalvo AL, Filocamo M, Vlahovicek K, Dardis A, Lualdi S, Corsolini F, Bembi B, Pittis MG. Molecular analysis of the HEXA gene in Italian patients with infantile and late onset Tay-Sachs disease: detection of fourteen novel alleles. Hum Mutat. 2005 Sep;26(3):282. (
  • Myerowitz R, Lawson D, Mizukami H, Mi Y, Tifft CJ, Proia RL. Molecular pathophysiology in Tay-Sachs and Sandhoff diseases as revealed by gene expression profiling. Hum Mol Genet. 2002 May 15;11(11):1343-50. (
  • NCBI Gene (


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: September 2008
Published: February 1, 2016