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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 GM2A gene?

The official name of this gene is “GM2 ganglioside activator.”

GM2A is the gene's official symbol. The GM2A gene is also known by other names, listed below.

What is the normal function of the GM2A gene?

The GM2A gene provides instructions for making a protein called the GM2 ganglioside activator. This protein is necessary for the normal function of an enzyme called beta-hexosaminidase A, which plays a critical role in the brain and spinal cord (central nervous system). Beta-hexosaminidase A and the GM2 ganglioside activator protein work together in lysosomes, which are structures in cells that break down toxic substances and act as recycling centers. Within lysosomes, the activator protein binds to a fatty substance called GM2 ganglioside and presents it to beta-hexosaminidase A to be broken down.

How are changes in the GM2A gene related to health conditions?

GM2-gangliosidosis, AB variant - caused by mutations in the GM2A gene

Only a few mutations in the GM2A gene have been identified in people with GM2-gangliosidosis, AB variant. Some of these mutations change single protein building blocks (amino acids) in the GM2 ganglioside activator. Other mutations delete a small amount of DNA from the GM2A gene. These genetic changes result in an unstable activator protein that is quickly degraded, or they prevent the gene from making any functional protein. Without the GM2 ganglioside activator, beta-hexosaminidase A is unable to break 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 the AB variant.

Where is the GM2A gene located?

Cytogenetic Location: 5q33.1

Molecular Location on chromosome 5: base pairs 151,253,052 to 151,270,394

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

The GM2A gene is located on the long (q) arm of chromosome 5 at position 33.1.

The GM2A gene is located on the long (q) arm of chromosome 5 at position 33.1.

More precisely, the GM2A gene is located from base pair 151,253,052 to base pair 151,270,394 on chromosome 5.

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

Where can I find additional information about GM2A?

You and your healthcare professional may find the following resources about GM2A 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 GM2A gene or gene products?

  • cerebroside sulfate activator protein
  • GM2 activator
  • GM2 ganglioside activator protein
  • SAP-3
  • sphingolipid activator protein 3

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

What glossary definitions help with understanding GM2A?

acids ; central nervous system ; DNA ; enzyme ; gene ; nervous system ; protein ; sulfate ; toxic

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


  • Chen B, Rigat B, Curry C, Mahuran DJ. Structure of the GM2A gene: identification of an exon 2 nonsense mutation and a naturally occurring transcript with an in-frame deletion of exon 2. Am J Hum Genet. 1999 Jul;65(1):77-87. (
  • Mahuran DJ. Biochemical consequences of mutations causing the GM2 gangliosidoses. Biochim Biophys Acta. 1999 Oct 8;1455(2-3):105-38. Review. (
  • Mahuran DJ. The GM2 activator protein, its roles as a co-factor in GM2 hydrolysis and as a general glycolipid transport protein. Biochim Biophys Acta. 1998 Jul 31;1393(1):1-18. Review. (
  • NCBI Gene (
  • Schepers U, Glombitza G, Lemm T, Hoffmann A, Chabas A, Ozand P, Sandhoff K. Molecular analysis of a GM2-activator deficiency in two patients with GM2-gangliosidosis AB variant. Am J Hum Genet. 1996 Nov;59(5):1048-56. (
  • Wendeler M, Werth N, Maier T, Schwarzmann G, Kolter T, Schoeniger M, Hoffmann D, Lemm T, Saenger W, Sandhoff K. The enzyme-binding region of human GM2-activator protein. FEBS J. 2006 Mar;273(5):982-91. (


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