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HEXA gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

HEXA gene

The HEXA gene provides instructions for creating a subunit of the enzyme beta-hexosaminidase A, which is critical for breaking down fatty substances in the brain and spinal cord.

Normal Function

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 beta-hexosaminidase A 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 found in cell membranes.

Health Conditions Related to Genetic Changes

Tay-Sachs disease

More than 210 variants that cause Tay-Sachs disease have been identified in the HEXA gene. Tay-Sachs disease is a condition characterized by movement disorders, intellectual and developmental disability, and other neurological problems caused by the death of nerve cells (neurons) in the central nervous system.

The HEXA gene variants that cause Tay-Sachs disease eliminate or severely reduce the activity of the enzyme beta-hexosaminidase A. This lack of enzyme activity prevents the enzyme from breaking down GM2 ganglioside. As a result, this substance builds up to toxic levels, particularly in neurons in the central nervous system. Progressive damage caused by the buildup of GM2 ganglioside leads to the destruction of these cells.

  • Infantile Tay-Sachs disease: Most known variants result in a completely nonfunctional version of the enzyme, leading to this severe form that appears in infancy.
  • Juvenile and late-onset forms: Other variants severely reduce but do not eliminate the activity of beta-hexosaminidase A, leading to less severe forms that appear later in life.

Other Names for This Gene

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

Frequently Asked Questions

Lysosomes are cellular structures that act as recycling centers, breaking down toxic substances and waste materials. In the context of Tay-Sachs disease, the lysosomes contain the beta-hexosaminidase A enzyme. When the HEXA gene mutation prevents the formation of a functional enzyme, the lysosomes cannot break down GM2 ganglioside. This failure leads to the toxic buildup of this fatty substance inside the cell, ultimately causing the destruction of the neuron.
The HEXA gene produces the alpha subunit of the beta-hexosaminidase A enzyme, which is vital for breaking down GM2 ganglioside within lysosomes. When this enzyme is nonfunctional due to HEXA mutations, GM2 ganglioside accumulates to toxic levels specifically in neurons of the brain and spinal cord. This buildup causes progressive damage and eventual death of these nerve cells, leading to the severe neurological symptoms characteristic of the disease.
The beta-hexosaminidase A enzyme is a complex made of two distinct parts: the alpha subunit, which is produced by the HEXA gene, and the beta subunit, which is produced by the HEXB gene. Both subunits must join together to form a functional enzyme. Mutations in either the HEXA or HEXB gene can disrupt this pairing, leading to a lack of enzyme activity and the subsequent accumulation of fatty substances in the body.
Infantile Tay-Sachs disease is caused by variants in the HEXA gene that result in a completely nonfunctional version of the beta-hexosaminidase A enzyme. This total loss of activity leads to rapid and severe accumulation of GM2 ganglioside, causing early onset of symptoms and rapid neurological decline. In contrast, other forms of the disease may involve residual enzyme activity, which can lead to a slower progression of symptoms.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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