On this page
GNPTG
N-acetylglucosamine-1-phosphate transferase subunit gamma
The GNPTG gene provides instructions for the gamma subunit of N-acetylglucosamine-1-phosphotransferase, an enzyme critical for directing digestive enzymes to cellular lysosomes. GNPTG encodes a subunit of an enzyme called GlcNAc-1-phosphotransferase, which plays a vital role in cellular waste recycling by tagging enzymes for delivery to lysosomes.
GNPTG is located on the short (p) arm of chromosome 16, at band 16p13.3. Arm ratio per GRCh38 - banding schematic.
Explore chromosome 16 in the library →Available at Jeen Health
Clinical tests that include this
Overview
The GNPTG gene, or N-acetylglucosamine-1-phosphate transferase subunit gamma, is essential for normal cellular function, particularly in the process of enzyme targeting within cells. It provides the genetic blueprint for one of the subunits of a crucial enzyme known as GlcNAc-1-phosphotransferase. This enzyme is responsible for modifying specific digestive enzymes, marking them for transport to lysosomes, which are cellular compartments that break down waste products.
What the gene does
The enzyme GlcNAc-1-phosphotransferase, composed of alpha, beta, and gamma subunits, initiates the creation of mannose-6-phosphate (M6P) tags. The GNPTG gene specifically codes for the gamma subunit of this enzyme. The M6P tag acts as a molecular address label, ensuring that newly synthesised digestive enzymes, known as hydrolases, are correctly delivered to the lysosomes. Without proper tagging, these hydrolases may not reach their intended destination, leading to their increased presence outside the cell and a deficiency within the lysosomes. This can result in an accumulation of unprocessed molecules within the lysosomes, disrupting cellular processes.
Video: Genetics 101
Chromosome location
The GNPTG gene is situated on chromosome 16 at position 16p13.3. This specific location indicates its physical address on the short arm (p) of chromosome 16, within band 13.3.
Protein structure
The GNPTG gene encodes a protein consisting of 305 amino acids. This protein contains several functional regions. From amino acids 69-171, there is a MRH (Mannose-6-Phosphate Receptor Homology) domain. Following this, a DMAP1-binding domain is located between amino acids 176-279. The C-terminal region, spanning amino acids 267-305, is characterised as a disordered region.
Key variants
Genetic variations within the GNPTG gene can alter the function of the GlcNAc-1-phosphotransferase enzyme. These changes may reduce the enzyme's activity, impacting its ability to correctly tag lysosomal enzymes. Such variations are typically inherited in an autosomal recessive pattern, meaning an individual must inherit two altered copies of the gene (one from each parent) to be affected.
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.203C>A | p.Ser68Ter | Pathogenic/Likely pathogenic | ★★☆☆ | GNPTG-related disorder |
c.234-1G>C | - | Pathogenic | ★★☆☆ | GNPTG-mucolipidosis |
c.384_385dup | p.Cys129fs | Pathogenic/Likely pathogenic | ★★☆☆ | GNPTG-mucolipidosis |
c.461_465del | p.Pro154fs | Pathogenic/Likely pathogenic | ★★☆☆ | GNPTG-mucolipidosis |
c.514dup | p.His172fs | Pathogenic | ★★☆☆ | GNPTG-mucolipidosis |
c.559C>T | p.Gln187Ter | Pathogenic/Likely pathogenic | ★★☆☆ | GNPTG-mucolipidosis |
c.607C>T | p.Gln203Ter | Pathogenic | ★★☆☆ | GNPTG-mucolipidosis |
c.610-1G>A | - | Pathogenic | ★★☆☆ | GNPTG-mucolipidosis |
c.638_639del | p.Leu212_Phe213insTer | Pathogenic/Likely pathogenic | ★★☆☆ | GNPTG-related disorder |
c.701del | p.Pro234fs | Pathogenic/Likely pathogenic | ★★☆☆ | GNPTG-mucolipidosis |
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
Variations in the GNPTG gene are associated with inherited metabolic conditions. Specifically, mutations in this gene are known to cause mucolipidosis III gamma. This condition arises from the impaired targeting of digestive enzymes to lysosomes, leading to their accumulation outside the cell and subsequent cellular dysfunction.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic GNPTG 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
The GNPTG gene is recognised in the UK for its clinical relevance, featuring on several NHS Genomic Medicine Service national test panels. These include panels for conditions such as Foetal anomalies (R21), Intellectual disability, Lysosomal storage disorder (R276), Skeletal dysplasia (R104), and Retinal disorders (R32). It is also part of panels for Undiagnosed metabolic disorders, Mucopolysaccharidosis, Gaucher, Fabry, and is listed in the DDG2P (Deciphering Developmental Disorders Gene to Phenotype) database.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the primary function of the GNPTG gene?
The GNPTG gene provides instructions for making the gamma subunit of an enzyme called GlcNAc-1-phosphotransferase. This enzyme is crucial for tagging digestive enzymes with mannose-6-phosphate, directing them to lysosomes for waste breakdown.
What happens if the GNPTG gene doesn't function correctly?
If the GNPTG gene has pathogenic variants, the GlcNAc-1-phosphotransferase enzyme may have reduced activity. This can disrupt the proper targeting of digestive enzymes to lysosomes, leading to their accumulation outside the cell and causing conditions such as mucolipidosis III gamma.
How is mucolipidosis III gamma inherited?
Mucolipidosis III gamma is typically inherited in an autosomal recessive manner. This means an individual must inherit two copies of the altered GNPTG gene, one from each parent, to develop the condition.
References
- Persichetti E, Chuzhanova NA, Dardis A. Identification and molecular characterization of six novel mutations in the UDP-N-acetylglucosamine-1-phosphotransferase gamma subunit (GNPTG) gene in patients with mucolipidosis III gamma. Human mutation. 2009. PMID: 19370764
- Pohl S, Tiede S, Castrichini M. Compensatory expression of human N-acetylglucosaminyl-1-phosphotransferase subunits in mucolipidosis type III gamma. Biochimica et biophysica acta. 2009. PMID: 19708128
- Raas-Rothschild A, Bargal R, Goldman O. Genomic organisation of the UDP-N-acetylglucosamine-1-phosphotransferase gamma subunit (GNPTAG) and its mutations in mucolipidosis III. Journal of medical genetics. 2004. PMID: 15060128
- Raas-Rothschild A, Cormier-Daire V, Bao M. Molecular basis of variant pseudo-hurler polydystrophy (mucolipidosis IIIC). The Journal of clinical investigation. 2000. PMID: 10712439