On this page
GLB1
galactosidase beta 1
The GLB1 gene provides instructions for producing the beta-galactosidase enzyme, which is vital for cellular waste recycling and preventing the accumulation of harmful substances. The GLB1 gene encodes the beta-galactosidase enzyme, located within cellular lysosomes, where it breaks down specific molecules including GM1 ganglioside and keratan sulphate.
GLB1 is located on the short (p) arm of chromosome 3, at band 3p22.3. Arm ratio per GRCh38 - banding schematic.
Explore chromosome 3 in the library →Available at Jeen Health
Clinical tests that include this
Overview
The GLB1 gene, full name galactosidase beta 1, is essential for cellular health, primarily by producing an enzyme known as beta-galactosidase. This enzyme plays a crucial role in the lysosomes, which are cellular compartments responsible for breaking down and recycling various molecules. Deficiencies in this enzyme can lead to the build-up of certain substances within cells, contributing to inherited conditions.
What the gene does
The GLB1 gene provides instructions for two distinct proteins. The primary protein is beta-galactosidase (β-galactosidase), an enzyme situated in lysosomes, where it facilitates the breakdown of specific molecules. These include GM1 ganglioside, which is important for healthy nerve cell function in the brain, and keratan sulphate, a large sugar molecule (glycosaminoglycan) abundant in cartilage and the cornea of the eye. Breakdown of these molecules is critical for preventing their harmful accumulation.
The GLB1 gene also directs the production of a smaller protein, elastin-binding protein (EBP), found on cell surfaces. EBP interacts with other proteins, cathepsin A and neuraminidase 1, forming the elastin receptor complex. This complex contributes to the formation of elastic fibres, which are key components of the body's connective tissues.
Video: Genetics 101
Chromosome location
The GLB1 gene is located on chromosome 3 at position 3p22.3. It spans a region of the short arm of chromosome 3. The protein produced from this gene is 677 amino acids in length.
Protein structure
The GLB1 gene encodes a protein with a total length of 677 amino acids. While the full domain architecture is not extensively characterised, a specific Disordered Region has been identified towards the C-terminal end, spanning amino acids 650-677.
Key variants
Pathogenic variants in the GLB1 gene can disrupt the normal function of the proteins it encodes, particularly the beta-galactosidase enzyme. These genetic changes can range from single DNA building block alterations to larger deletions or insertions, impacting enzyme activity or protein stability. Such variants interfere with the cell's ability to properly break down specific molecules, leading to their accumulation.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.1071_1073delinsGG | p.Phe357fs | Pathogenic/Likely pathogenic | ★★☆☆ | Infantile GM1 gangliosidosis |
c.1147A>T | p.Lys383Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Mucopolysaccharidosis, MPS-IV-B |
c.1398_1399del | p.Gly467fs | Pathogenic/Likely pathogenic | ★★☆☆ | Mucopolysaccharidosis, MPS-IV-B |
c.1480-1G>C | - | Pathogenic/Likely pathogenic | ★★☆☆ | GM1 gangliosidosis type 2 |
c.1577del | p.Gly526fs | Pathogenic/Likely pathogenic | ★★☆☆ | Mucopolysaccharidosis, MPS-IV-B |
c.452A>T | p.Asp151Val | Pathogenic/Likely pathogenic | ★★☆☆ | Mucopolysaccharidosis, MPS-IV-B |
c.562G>T | p.Glu188Ter | Pathogenic | ★★☆☆ | Infantile GM1 gangliosidosis |
c.710A>G | p.Tyr237Cys | Pathogenic/Likely pathogenic | ★★☆☆ | Mucopolysaccharidosis, MPS-IV-B |
c.785G>A | p.Gly262Glu | Pathogenic/Likely pathogenic | ★★☆☆ | Mucopolysaccharidosis, MPS-IV-B |
c.785G>T | p.Gly262Val | Pathogenic/Likely pathogenic | ★★☆☆ | Mucopolysaccharidosis, MPS-IV-B |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Variants within the GLB1 gene are primarily associated with GM1 gangliosidosis, a lysosomal storage disorder characterised by the progressive accumulation of GM1 ganglioside. These genetic changes typically impair the production or function of both beta-galactosidase and elastin-binding protein. Additionally, certain GLB1 variants can cause Mucopolysaccharidosis Type IV, a condition mainly affecting the skeleton, where the breakdown of keratan sulphate is disrupted while GM1 ganglioside processing remains unaffected.
Inheritance pattern
Conditions caused by pathogenic GLB1 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
In the UK, the GLB1 gene is included on several NHS Genomic Medicine Service national panels, indicating its clinical significance. It is listed as 'green' for conditions such as GM1 Gangliosidosis and Mucopolysaccharidosis Type IVB (R288), Lysosomal storage disorder (R276), and Foetal anomalies (R21). GLB1 is also relevant for investigations into early onset or syndromic epilepsy, intellectual disability, and various forms of leukodystrophy and movement disorders.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the primary function of the GLB1 gene?
The GLB1 gene primarily provides instructions for producing the beta-galactosidase enzyme. This enzyme is crucial for breaking down complex molecules like GM1 ganglioside and keratan sulphate within cellular lysosomes.
What conditions are associated with variants in the GLB1 gene?
Variants in the GLB1 gene are mainly associated with GM1 gangliosidosis, a severe lysosomal storage disorder. Some variants can also cause Mucopolysaccharidosis Type IV, which primarily affects skeletal development.
How does GLB1 relate to carrier screening?
GLB1 is classified as an autosomal recessive gene, meaning that individuals who inherit one pathogenic variant are typically carriers and do not show symptoms. Carrier screening identifies these individuals who have an increased risk of having a child affected by a GLB1-related condition if their partner is also a carrier.
References
- Hofer D, Paul K, Fantur K. Phenotype determining alleles in GM1 gangliosidosis patients bearing novel GLB1 mutations. Clinical genetics. 2010. PMID: 20175788
- Hofer D, Paul K, Fantur K. GM1 gangliosidosis and Morquio B disease: expression analysis of missense mutations affecting the catalytic site of acid beta-galactosidase. Human mutation. 2009. PMID: 19472408
- Duca L, Blanchevoye C, Cantarelli B. The elastin receptor complex transduces signals through the catalytic activity of its Neu-1 subunit. The Journal of biological chemistry. 2007. PMID: 17327233
- Santamaria R, Chabás A, Callahan JW. Expression and characterization of 14 GLB1 mutant alleles found in GM1-gangliosidosis and Morquio B patients. Journal of lipid research. 2007. PMID: 17664528