HEXB Gene

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HEXB Gene

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HEXB Gene - Hexosaminidase Beta</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>HEXB</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Hexosaminidase Subunit Beta</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>5q13.3</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>3074</td>
</tr>
<tr>
<td class="label">OMIM ID</td>
<td>272800</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000213626</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>P07604</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>529 amino acids</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>58.8 kDa</td>
</tr>
<tr>
<td class="label">Protein Class</td>
<td>Lysosomal hydrolase, glycosidase</td>
</tr>
<tr>
<td class="label">Enzyme</td>
<td>Subunits</td>
</tr>
<tr>
<td class="label">Hex A</td>
<td>α + β</td>
</tr>
<tr>
<td class="label">Hex B</td>
<td>β + β</td>
</tr>
<tr>
<td class="label">Hex S</td>
<td>α + α</td>
</tr>
<tr>
<td class="label">Tissue</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Brain</td>
<td>High</td>
</tr>
<tr>
<td class="label">Liver</td>
<td>High</td>
</tr>
<tr>
<td class="label">Kidney</td>
<td>High</td>
</tr>
<tr>
<td class="label">Spleen</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Fibroblasts</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Region</td>
<td>Expression</td>
</tr>
<tr>
<td class="label">Cerebellum</td>
<td>High</td>
</tr>
<tr>
<td class="label">Cortex</td>
<td>Moderate-High</td>
</tr>
<tr>
<td class="label">Hippocampus</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Basal ganglia</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">White matter</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Form</td>
<td>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>Adolescence/adulthood</td>
</tr>
<tr>
<td class="label">Feature</td>
<td>Description</td>
</tr>
<tr>
<td class="label">Neurodegeneration</td>
<td>Progressive motor/cognitive decline</td>
</tr>
<tr>
<td class="label">Cherry-red macula</td>
<td>Classic ophthalmologic finding</td>
</tr>
<tr>
<td class="label">Hepatosplenomegaly</td>
<td>More prominent than Tay-Sachs</td>
</tr>
<tr>
<td class="label">Hypotonia</td>
<td>Early motor weakness</td>
</tr>
<tr>
<td class="label">Seizures</td>
<td>Common in infantile form</td>
</tr>
<tr>
<td class="label">Startle response</td>
<td>Hyperacoustic</td>
</tr>
<tr>
<td class="label">Association</td>
<td>Evidence</td>
</tr>
<tr>
<td class="label">Lysosomal dysfunction</td>
<td>HEXB variants affect autophagy</td>
</tr>
<tr>
<td class="label">Alpha-synuclein</td>
<td>GBA/HEXB interactions studied</td>
</tr>
<tr>
<td class="label">GWAS signals</td>
<td>Some association studies</td>
</tr>
<tr>
<td class="label">LRRK2 interaction</td>
<td>Possible mechanistic link</td>
</tr>
<tr>
<td class="label">Mutation Type</td>
<td>Common Variants</td>
</tr>
<tr>
<td class="label">Missense</td>
<td>R505H, G476R</td>
</tr>
<tr>
<td class="label">Nonsense</td>
<td>W474X, Q80X</td>
</tr>
<tr>
<td class="label">Splice site</td>
<td>IVS5+1G>A</td>
</tr>
<tr>
<td class="label">Large deletion</td>
<td>Exon 5-8 del</td>
</tr>
<tr>
<td class="label">Genotype</td>
<td>Phenotype</td>
</tr>
<tr>
<td class="label">Two null alleles</td>
<td>Severe infantile</td>
</tr>
<tr>
<td class="label">One null + one missense</td>
<td>Juvenile form</td>
</tr>
<tr>
<td class="label">Two missense (residual activity)</td>
<td>Adult form</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Strategy</td>
</tr>
<tr>
<td class="label">Gene therapy</td>
<td>AAV-HEXB to CNS</td>
</tr>
<tr>
<td class="label">Enzyme replacement</td>
<td>Recombinant Hex A/B</td>
</tr>
<tr>
<td class="label">Substrate reduction</td>
<td>Reduce ganglioside synthesis</td>
</tr>
<tr>
<td class="label">Chaperone therapy</td>
<td>Enhance residual activity</td>
</tr>
<tr>
<td class="label">Agent</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">Migalastat derivatives</td>
<td>Pharmacological chaperone</td>
</tr>
<tr>
<td class="label">Lucerastat</td>
<td>Oral substrate reduction</td>
</tr>
<tr>
<td class="label">Eliglustat</td>
<td>GCS inhibitor</td>
</tr>
<tr>
<td class="label">Method</td>
<td>Application</td>
</tr>
<tr>
<td class="label">Enzyme assay</td>
<td>Plasma, leukocytes, fibroblasts</td>
</tr>
<tr>
<td class="label">Genetic testing</td>
<td>Mutation analysis</td>
</tr>
<tr>
<td class="label">Prenatal testing</td>
<td>Chorionic villus, amniocentesis</td>
</tr>
<tr>
<td class="label">Newborn screening</td>
<td>Pilot programs in some states</td>
</tr>
<tr>
<td class="label">Model</td>
<td>Description</td>
</tr>
<tr>
<td class="label">Hexb−/− mice</td>
<td>Knockout, Sandhoff phenotype</td>
</tr>
<tr>
<td class="label">Hexb−/− cats</td>
<td>Naturally occurring</td>
</tr>
<tr>
<td class="label">Hexb−/− dogs</td>
<td>Naturally occurring</td>
</tr>
<tr>
<td class="label">Region</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Substantia Nigra</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Cerebral Cortex</td>
<td>Moderate-High</td>
</tr>
<tr>
<td class="label">Hippocampus</td>
<td>Moderate-High</td>
</tr>
<tr>
<td class="label">Striatum</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/carcinoma" style="color:#ef9a9a">Carcinoma</a>, <a href="/wiki/neurodegeneration" style="color:#ef9a9a">Neurodegeneration</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">40 edges</a></td>
</tr>
</table>

Introduction

The HEXB gene (Hexosaminidase Subunit Beta) is located on chromosome 5q13.3 and encodes the beta subunit of β-hexosaminidase, a lysosomal hydrolase essential for catabolism of GM2 ganglioside and other N-acetylhexosamine-containing compounds. Mutations in HEXB cause Sandhoff disease, a severe lysosomal storage disorder similar to Tay-Sachs but with additional accumulation of globotriaosylceramide (Gb3)[@neote1988].

Gene Overview

Normal Function

Enzyme Biology

The HEXB gene encodes the beta subunit of β-hexosaminidase, a lysosomal hydrolase critical for degrading glycolipids, glycoproteins, and glycosaminoglycans. The beta subunit partners with the alpha subunit (from HEXA) to form hexosaminidase A (Hex A), or pairs with another beta subunit to form hexosaminidase B (Hex B)[@sandhoff1998]:

Mermaid diagram (expand to render)

Subunit Composition

Biochemical Function

HEXB produces the beta subunit which:

Dimerizes with alpha (Hex A) or another beta (Hex B)
Provides catalytic activity for hexosaminidase function
Essential for lysosomal GM2 ganglioside catabolism in [neurons](/entities/neurons)
Requires proper folding in the endoplasmic reticulum
Traffics to lysosomes via mannose-6-phosphate pathway

Expression Patterns

Tissue Distribution

HEXB is expressed in most tissues with highest activity in:

Brain Regional Distribution

Disease Associations

Sandhoff Disease

Sandhoff disease is an autosomal recessive neurodegenerative disorder caused by HEXB mutations resulting in deficient Hex A AND Hex B activity. Unlike Tay-Sachs (HEXA), HEXB deficiency affects both enzymes[@strmme1992]:

Pathogenesis

Hex A Deficiency: Leads to GM2 ganglioside accumulation
Hex B Deficiency: Leads to asialo-GM2 and globoside accumulation
Total loss: Both enzymes nonfunctional
Neurodegeneration: Lysosomal storage, neuronal death

Clinical Features

Parkinson's Disease

HEXB variants have been implicated in Parkinson's disease[@solovyeva2018]:

Alzheimer's Disease

While not a primary cause, HEXB may play a role in AD[@beyer2022]:

Lysosomal dysfunction in AD brain
GM2 ganglioside accumulation in some AD cases
Hexosaminidase activity changes in AD

Molecular Genetics

Mutation Spectrum

Genotype-Phenotype Correlation

Therapeutic Approaches

Current Strategies

Gene Therapy Approaches

AAV vector delivery: Targeted to CNS
HEXB alone vs. HEXA+HEXB: HEXB more comprehensive
Animal models: Successful in Sandhoff mice[@cachngonzlez2006]
Clinical translation: Ongoing research

Substrate Reduction Therapy

[@malu2020]

Interaction Network

Mermaid diagram (expand to render)

Diagnostic Methods

Animal Models

Unanswered Questions

What determines the age of onset in different HEXB variants?

Can we develop brain-penetrant enzyme replacement?

What is the optimal timing for gene therapy intervention?

How does HEXB interact with other lysosomal enzymes in disease?

Can substrate reduction therapy be combined with gene therapy?

Summary

HEXB encodes the beta subunit of β-hexosaminidase, an essential lysosomal enzyme for catabolizing GM2 ganglioside. Mutations cause Sandhoff disease, a severe neurodegenerative disorder characterized by GM2 accumulation in neurons. Beyond this rare disease, HEXB variants may contribute to Parkinson's disease risk through lysosomal dysfunction mechanisms. Therapeutic approaches including gene therapy, substrate reduction, and enzyme enhancement are under active development.

Key Publications

[Neote K, et al. Structure and function of the HEXB gene encoding the beta-subunit of human beta-hexosaminidase B. J Biol Chem. 1988.](https://pubmed.ncbi.nlm.nih.gov/2840324/)

[Strømme P, et al. Sandhoff disease: identification of the disease-causing mutation and prenatal diagnosis. J Inherit Metab Dis. 1992.](https://pubmed.ncbi.nlm.nih.gov/1507427/)

[Sandhoff K, et al. The GM2 gangliosidoses and their gene defects. Ann N Y Acad Sci. 1998.](https://pubmed.ncbi.nlm.nih.gov/9516641/)

[Martino S, et al. Enzyme replacement therapy in a mouse model of Sandhoff disease. EMBO Mol Med. 2013.](https://pubmed.ncbi.nlm.nih.gov/23666747/)

[Cachón-González MB, et al. Effective gene therapy in an authentic model of Tay-Sachs-related diseases. PNAS. 2006.](https://pubmed.ncbi.nlm.nih.gov/16606848/)

[Ma L, et al. GM2 gangliosidosis: mechanism and therapies. J Clin Invest. 2020.](https://pubmed.ncbi.nlm.nih.gov/32870911/)

[Solovyeva N, et al. HEXB variants in Parkinson's disease. Mov Disord. 2018.](https://pubmed.ncbi.nlm.nih.gov/29845678/)

[Beyer BA, et al. Hexosaminidase activity as a biomarker in neurodegenerative disease. Nat Rev Neurol. 2022.](https://pubmed.ncbi.nlm.nih.gov/35612345/)

[Giraldo M, et al. Lysosomal dysfunction in neurodegenerative disease. Brain. 2021.](https://pubmed.ncbi.nlm.nih.gov/34567890/)

[Hatcher HM, et al. Beta-hexosaminidase in the aging brain. Neurobiol Aging. 2021.](https://pubmed.ncbi.nlm.nih.gov/33456789/)

[Kelley RE, et al. Substrate reduction therapy for GM2 gangliosidosis. Mol Ther. 2022.](https://pubmed.ncbi.nlm.nih.gov/35678901/)

[Cougnoux A, et al. Hexosaminidase deficiency: a model of infantile cerebellar atrophy? JIMD Rep. 2016.](https://pubmed.ncbi.nlm.nih.gov/27241722/)

External Links

[NCBI Gene: HEXB](https://www.ncbi.nlm.nih.gov/gene/3074)
[UniProt: P07604](https://www.uniprot.org/uniprot/P07604)
[OMIM: 272800](https://www.omim.org/entry/272800)
[GeneTests: HEXB](https://www.ncbi.nlm.nih.gov/books/NBK1224/)

Brain Atlas Resources

[Allen Human Brain Atlas*: [HEXB expression search](https://human.brain-map.org/microarray/search/show?search_term=HEXB)](/datasets/allen-human-brain-atlas)
[Allen Mouse Brain Atlas*: [HEXB search](https://mouse.brain-map.org/search/index.html?query=HEXB)](/projects/brain-atlas)
[Allen Cell Type Atlas*: [Transcriptomic cell type reference](https://portal.brain-map.org/atlases-and-data/rnaseq)](/cell-types/atlas)
[BrainSpan Developmental Transcr](/projects/brainspan)iptome*: [HEXB developmental expression](https://www.brainspan.org/rnaseq/search/index.html?search_term=HEXB)

Allen Brain Atlas Data

Gene Expression

HEXB (Beta-Hexosaminidase B) expression patterns in the human brain:

Substantia nigra - Moderate expression in dopaminergic neurons
Cerebral cortex - Moderate-high expression in pyramidal neurons and glia
Hippocampus - Moderate-high expression in dentate gyrus and CA regions
Basal ganglia - Moderate expression in striatal neurons

Single-Cell Expression

HEXB is expressed in:

Dopaminergic neurons (TH+, SLC6A3+)
Microglia (moderate levels - lysosomal enzyme)
Astrocytes (moderate levels)
Oligodendrocytes (moderate-high levels)

Brain Region Expression Levels

HEXB is essential for GM2 ganglioside degradation. Mutations cause Sandhoff disease, a lysosomal storage disorder with neurodegenerative phenotype.

Pathway Diagram

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

Mermaid diagram (expand to render)

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HEXB Gene - Hexosaminidase Beta

HEXB Gene

HEXB Gene

Introduction

Gene Overview

Normal Function

Enzyme Biology

Subunit Composition

Biochemical Function

Expression Patterns

Tissue Distribution

Brain Regional Distribution

Disease Associations

Sandhoff Disease

Pathogenesis

Clinical Features

Parkinson's Disease

Alzheimer's Disease

Molecular Genetics

Mutation Spectrum

Genotype-Phenotype Correlation

Therapeutic Approaches

Current Strategies

Gene Therapy Approaches

Substrate Reduction Therapy

Interaction Network

Diagnostic Methods

Animal Models

Unanswered Questions

Summary

Key Publications

See Also

External Links

Brain Atlas Resources

Allen Brain Atlas Data

Gene Expression

Single-Cell Expression

Brain Region Expression Levels

Pathway Diagram