URL of this page: https://medlineplus.gov/genetics/gene/gm2a/

GM2A gene

ganglioside GM2 activator

Normal Function

The GM2A gene provides instructions for making a protein called the ganglioside GM2 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 ganglioside GM2 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.

Health Conditions Related to Genetic Changes

GM2-gangliosidosis, AB variant

A few variants (also called mutations) in the GM2A gene have been identified in people with GM2-gangliosidosis, AB variant. Some of these variants change single protein building blocks (amino acids) in the ganglioside GM2 activator. Other variants 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 ganglioside GM2 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.

More About This Health Condition

Other Names for This Gene

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

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


  • 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. doi: 10.1086/302463. Citation on PubMed or Free article on PubMed Central
  • Mahuran DJ. Biochemical consequences of mutations causing the GM2 gangliosidoses. Biochim Biophys Acta. 1999 Oct 8;1455(2-3):105-38. doi: 10.1016/s0925-4439(99)00074-5. Citation on PubMed
  • 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. doi: 10.1016/s0005-2760(98)00057-5. Citation on PubMed
  • 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. Citation on PubMed or Free article on PubMed Central
  • 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. doi: 10.1111/j.1742-4658.2006.05126.x. Citation on PubMed
  • Xiao C, Toro C, Tifft C. GM2 Activator Deficiency. 2022 Aug 25. In: Adam MP, Mirzaa GM, Pagon RA, Wallace SE, Bean LJH, Gripp KW, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2023. Available from http://www.ncbi.nlm.nih.gov/books/NBK583219/ Citation on PubMed

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