HEXA Gene - Hexosaminidase Alpha

HEXA Gene

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HEXA Gene - Hexosaminidase Alpha</th>
</tr>
<tr>
<td class="label">infobox</td>
<td>[@myerowitz1997]</td>
</tr>
<tr>
<td class="label">HEXA Gene</td>
<td>[@tifft2009]</td>
</tr>
<tr>
<td class="label">Symbol</td>
<td>HEXA</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>15q24.1</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>3073</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>272800</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000213626</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td>P06865</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td>Tay-Sachs Disease, AB Variant GM2 Gangliosidosis</td>
</tr>
<tr>
<td class="label">Form</td>
<td>Age of Onset</td>
</tr>
<tr>
<td class="label">Infantile</td>
<td>3-6 months</td>
</tr>
<tr>
<td class="label">Juvenile</td>
<td>2-5 years</td>
</tr>
<tr>
<td class="label">Adult (LADB)</td>
<td>Puberty/adolescence</td>
</tr>
</table>

Introduction

Hexa Gene Hexosaminidase Alpha is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

...

HEXA Gene

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HEXA Gene - Hexosaminidase Alpha</th>
</tr>
<tr>
<td class="label">infobox</td>
<td>[@myerowitz1997]</td>
</tr>
<tr>
<td class="label">HEXA Gene</td>
<td>[@tifft2009]</td>
</tr>
<tr>
<td class="label">Symbol</td>
<td>HEXA</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>15q24.1</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>3073</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>272800</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000213626</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td>P06865</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td>Tay-Sachs Disease, AB Variant GM2 Gangliosidosis</td>
</tr>
<tr>
<td class="label">Form</td>
<td>Age of Onset</td>
</tr>
<tr>
<td class="label">Infantile</td>
<td>3-6 months</td>
</tr>
<tr>
<td class="label">Juvenile</td>
<td>2-5 years</td>
</tr>
<tr>
<td class="label">Adult (LADB)</td>
<td>Puberty/adolescence</td>
</tr>
</table>

Introduction

Hexa Gene Hexosaminidase Alpha is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

The HEXA gene (Hexosaminidase Subunit Alpha) is located on chromosome 15q24.1 and encodes the alpha subunit of the lysosomal enzyme beta-hexosaminidase A (Hex A). This enzyme is essential for the catabolism of GM2 ganglioside, a major ganglioside in neuronal membranes. Mutations in HEXA cause Tay-Sachs disease, a fatal lysosomal storage disorder characterized by progressive neurodegeneration. The gene is part of a family of hexosaminidase genes that also includes HEXB, with which it forms the heterodimeric Hex A enzyme.

Function

The HEXA gene encodes the alpha subunit of the enzyme β-hexosaminidase A (Hex A), a lysosomal hydrolase essential for the catabolism of GM2 ganglioside and other glycoconjugates containing N-acetylhexosamines.

Hexosaminidase A is a heterodimer composed of an alpha (HEXA) and beta (HEXB) subunit. The enzyme functions within the acidic environment of lysosomes to hydrolyze:

• GM2 ganglioside: Major membrane glycolipid in neuronal cells
• Glycosaminoglycans: Heparin, chondroitin sulfate
• Glycoproteins: Various N-acetylhexosamine-containing substrates

Enzyme Complex

• Hex A (αβ): α subunit from HEXA + β subunit from HEXB
• Hex B (ββ): Two β subunits from HEXB
• Hex S (αα): Two α subunits (usually inactive without β)

The alpha subunit provides the catalytic site and is essential for Hex A activity. Mutations affecting the alpha subunit disrupt GM2 ganglioside catabolism, leading to accumulation in [neurons](/entities/neurons).

Disease Associations

Tay-Sachs Disease

Tay-Sachs disease is an autosomal recessive neurodegenerative disorder caused by HEXA mutations resulting in deficient Hex A activity. It is characterized by:

• GM2 Ganglioside Accumulation: Progressive accumulation in neuronal cytoplasm
• Cherry-Red Macula: Classic ophthalmologic finding
• Neurodegeneration: Progressive motor and cognitive decline
• Infantile Death: Typically fatal by age 2-4 years

Clinical Forms

AB Variant GM2 Gangliosidosis

A rare form caused by mutations in HEXA combined with deficiency of the GM2 activator protein, resulting in a similar phenotype to Tay-Sachs.

Other Associations

• Alzheimer's Disease: Hex A activity declines with age; potential role in [Aβ](/proteins/amyloid-beta) metabolism
• Parkinson's Disease: Some studies show altered hexosaminidase activity in PD brains

Expression

HEXA is expressed in most tissues with highest levels in:

• Brain (neurons, astrocytes)
• Liver
• Kidney
• Placenta

In the brain, HEXA expression is essential for maintaining GM2 ganglioside turnover in neurons. The enzyme is synthesized in the ER and trafficked to lysosomes via mannose-6-phosphate receptors.

Therapeutic Approaches

Enzyme Replacement Therapy

• Limited by blood-brain barrier: Cannot deliver enzyme to CNS
• Teverbal research: Modified enzymes with enhanced [BBB](/entities/blood-brain-barrier) penetration

Gene Therapy

• AAV-vector delivery: Experimental approaches targeting CNS
• Ex vivo gene therapy: Patient cells modified and reinfused
• CRISPR-based approaches: Potential for correction

Substrate Reduction Therapy

• Migalastat (Galafold): FDA-approved for Fabry disease, being explored for Tay-Sachs
• Lucerastat: Oral substrate reduction therapy in trials

Chaperone Therapy

• Pharmacological chaperones: Small molecules to enhance mutant enzyme folding and activity
• Pyrimethamine: Currently in clinical trials

Newborn Screening

• Enzyme activity testing: Allows early diagnosis
• Carrier screening: Important in at-risk populations (Ashkenazi Jewish descent)
• Preimplantation genetic diagnosis: Available for families

Background

The study of Hexa Gene Hexosaminidase Alpha has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

See Also

• [Tay-Sachs Disease - Primary disease association](/diseases/tay-sachs-disease)
• [HEXB Gene - Partner subunit gene](/genes/ar)
• [Sandhoff Disease - HEXB deficiency](/diseases/sandhoff-disease)
• [GM2 Gangliosidosis - Disease category](/proteins/ANG)
• [Lysosomal Storage Disorders - Related disorders](/diseases/lysosomal-storage-disorders)
• GM2 Activator Protein - Essential cofactor

External Links

• [NCBI Gene: HEXA](https://www.ncbi.nlm.nih.gov/gene/3073)
• [UniProt: P06865](https://www.uniprot.org/uniprot/P06865)
• [OMIM: 272800](https://www.omim.org/entry/272800)
• [GeneTests: HEXA](https://www.ncbi.nlm.nih.gov/books/NBK1192/)
• [NTSAD - National Tay-Sachs & Allied Diseases Association](https://www.ntsad.org/)

Allen Brain Atlas Data

Gene Expression

HEXA (Beta-hexosaminidase A subunit) expression data from the Allen Human Brain Atlas:

• [Cerebral cortex* - Moderate expression in pyramidal neurons](/brain-regions/cerebral-cortex)
• [Hippocampus* - Expression in CA regions and dentate gyrus](/brain-regions/hippocampus)
• [Cerebellum* - Pre](/brain-regions/cerebellum)sent in Purkinje cells
• White matter - Expression in oligodendrocytes

Single-Cell Expression

Single-cell transcriptomics data indicates HEXA (Beta-hexosaminidase A subunit) is expressed in:

• Oligodendrocytes and precursor cells
• Certain neuronal populations
• Microglial cells

External Resources

• [Allen Human Brain Atlas - Microarray](https://human.brain-map.org/microarray/gene/search?search_term=HEXA)
• [Single Cell Expression Atlas](https://www.ebi.ac.uk/gxa/sc/gene/HEXA)

References

References

Gravel RA, et al, The GM2 gangliosidoses (2001)

Myerowitz R, Tay-Sachs disease-causing mutations and neutral variants in the HEXA gene (1997)

Lemanski K, et al, Structure of human beta-hexosaminidase A (2003)

Tifft CJ, et al, Mouse models of GM2 activator deficiency and Tay-Sachs disease (2009)

Kakkis E, et al, Enzyme replacement therapy in a mouse model of Tay-Sachs disease (1996)

Pathway Diagram

The following diagram shows the key molecular relationships involving HEXA Gene - Hexosaminidase Alpha discovered through SciDEX knowledge graph analysis: