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GLA
galactosidase alpha
The GLA gene provides instructions for creating the alpha-galactosidase A enzyme, crucial for cellular waste recycling and lipid metabolism. The GLA gene is vital for cellular function, encoding the alpha-galactosidase A enzyme which breaks down specific fatty substances within lysosomes.
GLA is located on the long (q) arm of chromosome X, at band Xq22.1. Arm ratio per GRCh38 - banding schematic.
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Overview
The GLA gene, found on the X chromosome, directs the synthesis of an enzyme named alpha-galactosidase A. This enzyme is crucial for the cell's internal recycling system, specifically within organelles called lysosomes [PMID:33678082]. Lysosomes function as cellular waste disposal units, breaking down various molecules for degradation or subsequent cellular use.
Alpha-galactosidase A primarily acts on globotriaosylceramide, a molecule composed of three sugar units linked to a lipid. Effective functioning of this enzyme is essential for the normal catabolism of aged cellular components, including those from red blood cells. When alterations occur in the GLA gene, it can lead to impaired enzyme activity and the build-up of globotriaosylceramide inside cells, disrupting cellular processes.
What the gene does
The GLA gene's primary role is to provide the genetic blueprint for alpha-galactosidase A, which is a lysosomal hydrolase enzyme. This enzyme is essential for the catabolism (breakdown) of glycosphingolipids (complex fat molecules), especially globotriaosylceramide (Gb3 or GL-3) and related substances [PMID:33678082]. Within the lysosome, alpha-galactosidase A cleaves the terminal alpha-galactosyl residue from globotriaosylceramide.
This enzymatic action is critical for maintaining cellular homeostasis, as Gb3 is a common component of cell membranes and is produced during normal cell turnover. Without sufficient functional alpha-galactosidase A, Gb3 progressively accumulates within the lysosomes of various cell types throughout the body [PMID:33678082]. This accumulation impairs cellular structure and function, leading to a spectrum of symptoms and organ damage. The enzyme's precise mechanism involves catalysing the hydrolysis (a chemical reaction with water) of specific glycosidic bonds, effectively breaking down complex lipids into simpler components for further processing or excretion. Therefore, dysfunctional alpha-galactosidase A hinders the cell's ability to effectively manage its waste products.
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Chromosome location
The GLA gene is located on the long arm (q arm) of the X chromosome at position 22.1, denoted as Xq22.1. This genomic position indicates that the gene resides within the X chromosome's band 22.1. Its X-linked inheritance pattern typically results in differing presentations of associated conditions between males and females due to the variation in X chromosome dosage.
Protein structure
Detailed information regarding the domain architecture of the alpha-galactosidase A protein is not provided in the current grounding sources.
Key variants
Genetic variations within the GLA gene can significantly impact the production or function of the alpha-galactosidase A enzyme. Over 370 distinct genetic changes in GLA have been identified in individuals with Fabry disease. These variants can range from single base-pair changes that alter a specific amino acid in the enzyme to larger deletions or insertions of genetic material within the gene. Some variants may also introduce a premature stop signal, leading to a truncated and non-functional protein. The specific nature and location of a GLA variant can influence the severity of the resulting enzyme deficiency and the clinical presentation of the associated condition.
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.1000-1G>A | - | Pathogenic | ★★☆☆ | Fabry disease |
c.1000-1G>C | - | Pathogenic | ★★☆☆ | Fabry disease |
c.1018T>C | p.Trp340Arg | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1019_1020insA | p.Trp340Ter | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1019G>A | p.Trp340Ter | Pathogenic | ★★☆☆ | Fabry disease |
c.101A>G | p.Asn34Ser | Pathogenic | ★★☆☆ | Fabry disease |
c.1020G>A | p.Trp340Ter | Pathogenic | ★★☆☆ | Fabry disease |
c.1021del | p.Glu341fs | Pathogenic | ★★☆☆ | Fabry disease |
c.1021G>A | p.Glu341Lys | Pathogenic | ★★☆☆ | Fabry disease |
c.1021G>T | p.Glu341Ter | Pathogenic | ★★☆☆ | Fabry disease |
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
Pathogenic variants in the GLA gene are primarily associated with Fabry disease. This condition follows an X-linked inheritance pattern, meaning males are typically more severely affected as they have only one X chromosome, whilst females may experience a range of symptoms from mild to severe due to X-inactivation patterns. Fabry disease is a lysosomal storage disorder characterised by the accumulation of globotriaosylceramide within various tissues and organs due to insufficient alpha-galactosidase A activity. This accumulation can lead to a wide spectrum of health issues affecting the kidneys, heart, nervous system, and skin [PMID:33678082].
Inheritance pattern
Conditions caused by pathogenic GLA variants typically follow x-linked inheritance.
X-linked recessive: sons of a carrier mother have a 50% chance of being affected. Daughters have a 50% chance of being carriers.
UK clinical status
In the UK, the GLA gene is included on several NHS Genomic Medicine Service clinical panels, reflecting its importance in diagnosing a range of conditions. It is part of panels for conditions such as Cystic kidney disease, Fabry disease, Familial cerebral small vessel disease, and Hypertrophic cardiomyopathy. Its presence on these panels indicates that genetic testing for GLA variants is considered clinically relevant for individuals presenting with symptoms related to these disorders.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Diet & lifestyle considerations
Maintaining a healthy lifestyle, including a balanced diet and regular physical activity, supports overall health. For individuals with conditions related to GLA gene variants, managing symptoms and supporting organ health can be aided by general health practices. However, there is no conclusive evidence to suggest that specific lifestyle interventions can prevent the onset or progression of genetic conditions like Fabry disease. General medical advice often includes avoiding factors that might exacerbate symptoms and adhering to prescribed treatments.
Supplement considerations
While some individuals with chronic conditions may consider dietary supplements, there is no scientific evidence to support the use of specific supplements for preventing or treating conditions associated with GLA gene variants. Individuals should consult with a healthcare professional before taking any new supplements, as some may interact with medications or have adverse effects. A healthcare provider can offer personalised advice based on an individual's specific health needs and medical history.
Frequently asked questions
What is the function of the GLA gene?
The GLA gene provides instructions for making the alpha-galactosidase A enzyme, which is essential for breaking down globotriaosylceramide (Gb3) within cellular lysosomes. This process is vital for the cell's waste recycling system.
What condition is associated with the GLA gene?
Pathogenic variants in the GLA gene are associated with Fabry disease, an X-linked lysosomal storage disorder characterised by the accumulation of Gb3 in various tissues and organs.
How is Fabry disease inherited?
Fabry disease is inherited in an X-linked pattern. This means the gene is located on the X chromosome, and males are typically more severely affected than females, though females can experience a range of symptoms.
What are lysosomes and why are they important for GLA?
Lysosomes are organelles within cells that act as recycling centres, using digestive enzymes to break down waste products. The alpha-galactosidase A enzyme, encoded by GLA, functions in lysosomes to break down specific fatty substances.
Is the GLA gene included in UK genetic testing panels?
Yes, the GLA gene is part of several NHS Genomic Medicine Service clinical panels in the UK, including those for Fabry disease, Cystic kidney disease, and Hypertrophic cardiomyopathy, among others.
References
- Schäfer E, Baron K, Widmer U. Thirty-four novel mutations of the GLA gene in 121 patients with Fabry disease. Human mutation. 2005. PMID: 15776423
- Matsuzawa F, Aikawa S, Doi H. Fabry disease: correlation between structural changes in alpha-galactosidase, and clinical and biochemical phenotypes. Human genetics. 2005. PMID: 15924232
- Garman SC, Garboczi DN. The molecular defect leading to Fabry disease: structure of human alpha-galactosidase. Journal of molecular biology. 2004. PMID: 15003450
- Pastores GM, Lien YH. Biochemical and molecular genetic basis of Fabry disease. Journal of the American Society of Nephrology : JASN. 2002. PMID: 12068024
- Feldt-Rasmussen U, Rasmussen AK, Mersebach H. Fabry disease--a metabolic disorder with a challenge for endocrinologists? Hormone research. 2002. PMID: 12446988
- Adam MP, Bick S, Mirzaa GM. Fabry Disease. 1993. PMID: 20301469