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GNPTAB

N-acetylglucosamine-1-phosphate transferase subunits alpha and beta

The GNPTAB gene provides instructions for producing subunits of an enzyme critical for transporting digestive enzymes to lysosomes, cellular compartments responsible for waste breakdown. The GNPTAB gene encodes components of GlcNAc-1-phosphotransferase, an enzyme vital for tagging certain digestive enzymes.

Chromosome 12q23.2 Autosomal recessive HGNC:29670 Tier C
GNPTAB 12q23.2 p arm q arm 12

GNPTAB is located on the long (q) arm of chromosome 12, at band 12q23.2. Arm ratio per GRCh38 - banding schematic.

Explore chromosome 12 in the library →

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Clinical tests that include this

Carrier Screening panel
GNPTAB is 1 of 1,008 genes on this panel
Expanded carrier screening for recessive and X-linked conditions

Overview

The GNPTAB gene, fully known as N-acetylglucosamine-1-phosphate transferase subunits alpha and beta, is essential for normal cellular function. It plays a key role in the creation of a specific enzyme that helps transport other vital enzymes to lysosomes, which are often referred to as the 'recycling centres' of the cell. Pathogenic variants in GNPTAB are associated with severe inherited conditions, including mucolipidosis type II (I-cell disease) and type III, which are lysosomal storage disorders.

What the gene does

The GNPTAB gene provides the genetic blueprint for the alpha and beta subunits of the GlcNAc-1-phosphotransferase enzyme. This enzyme, composed of alpha, beta, and gamma subunits (the gamma subunit is encoded by a different gene, GNPTG), initiates the process of tagging lysosomal hydrolases. Specifically, GlcNAc-1-phosphotransferase adds a GlcNAc-1-phosphate molecule to newly synthesised hydrolases. This tag is then processed to form mannose-6-phosphate (M6P), which acts as a signal, directing these hydrolases to the lysosomes. Without correctly functioning GlcNAc-1-phosphotransferase, hydrolases cannot receive their M6P tag and are instead secreted outside the cell, leading to an accumulation of waste products within lysosomes and subsequent cellular dysfunction.

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Chromosome location

The GNPTAB gene is situated on chromosome 12 at position 12q23.2. This gene contains instructions for making a protein that is 1256 amino acids long.

Protein structure

The GNPTAB protein has a complex structure that includes several important domains. It features two LNR repeat regions, LNR 1 spanning amino acids 438-473, and LNR 2 from amino acids 505-545. A DMAP1-binding domain is located between amino acids 699-798, and an EF-hand domain is found from amino acids 1005-1040.

Domain map · 1,256 amino acids
LNR 1 (438–473)LNR 2 (505–545)DMAP1-binding (699–798)EF-hand (1005–1040)LNR 1438–473LNR 2505–545DMAP1-binding699–7981~6281,256
Repeat - repeating structural motif
Domain - independent functional unit
🧬 Explore 3D structure on AlphaFold
UniProt:Q3T906Length:1,256 aaStructure:AlphaFold

Key variants

Variants in the GNPTAB gene can alter the function of the GlcNAc-1-phosphotransferase enzyme, leading to a spectrum of inherited disorders. These genetic changes can range from small alterations in DNA sequence to larger deletions or duplications, impacting the production or activity of the enzyme's alpha and beta subunits. The specific effect on enzyme function typically dictates the severity and type of associated condition.

The table below shows the top 10 pathogenic or likely-pathogenic variants currently classified in ClinVar for GNPTAB.
View all on ClinVar →

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.1052dup
Duplication
 p.Asn351fs Pathogenic/Likely pathogenic ★★☆☆ Mucolipidosis type II
c.1364C>T
single nucleotide variant
 p.Ala455Val Pathogenic/Likely pathogenic ★★☆☆ Mucolipidosis type II
c.1609C>T
single nucleotide variant
 p.Gln537Ter Pathogenic/Likely pathogenic ★★☆☆ Mucolipidosis type II
c.1858_1880del
Deletion
 p.Thr620fs Pathogenic/Likely pathogenic ★★☆☆ Mucolipidosis type II
c.1947C>G
single nucleotide variant
 p.Tyr649Ter Pathogenic/Likely pathogenic ★★☆☆ Mucolipidosis type II
c.1A>T
single nucleotide variant
 p.Met1Leu Pathogenic/Likely pathogenic ★★☆☆ Mucolipidosis type II
c.2036dup
Duplication
 p.Arg680fs Pathogenic/Likely pathogenic ★★☆☆ Mucolipidosis type II
c.2363T>A
single nucleotide variant
 p.Leu788Ter Pathogenic/Likely pathogenic ★★☆☆ Mucolipidosis type II
c.249_267dup
Duplication
 p.Leu90delinsTrpHisArgSerTer Pathogenic ★★☆☆ Pseudo-Hurler polydystrophy
c.3159dup
Duplication
 p.Leu1054fs Pathogenic/Likely pathogenic ★★☆☆ Mucolipidosis type II

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 GNPTAB gene are primarily associated with mucolipidosis II (I-cell disease) and mucolipidosis III alpha/beta. These conditions are autosomal recessive lysosomal storage disorders, meaning an individual must inherit two affected copies of the gene to develop the disease. Mucolipidosis II generally presents with a more severe clinical picture, often due to a complete absence of functional GlcNAc-1-phosphotransferase, while mucolipidosis III results from reduced enzyme activity.

Inheritance pattern

Conditions caused by pathogenic GNPTAB variants typically follow autosomal recessive inheritance.

♀ Carrier parent 1 altered copy ♂ Carrier parent 1 altered copy Affected Carrier Carrier Unaffected Affected Carrier Unaffected Circles = females · Squares = males

When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.

Carrier frequency by population How common is heterozygous GNPTAB carrier status across ancestry groups?

UK clinical status

The GNPTAB gene is recognised on several UK NHS national genomic testing panels, indicating its clinical significance. It is included in panels for Foetal anomalies (R21), Foetal hydrops, Intellectual disability, Likely inborn error of metabolism (R98), Lysosomal storage disorder (R276), Mucolipidosis II and III Alpha or Beta (R289), Mucopolysaccharideosis, Gaucher, Fabry, Rare syndromic craniosynostosis or isolated multisuture synostosis (R100), Skeletal dysplasia (R104), and Undiagnosed metabolic disorders, as listed by NHS England's National Genomic Test Directory. This gene is also listed in DDG2P.

Green-listed
High evidence · clinically actionable in NHS testing
Included in NHS GMS signed-off panels
Fetal anomalies · R21 NHS GMS → Likely inborn error of metabolism · R98 NHS GMS → Lysosomal storage disorder · R276 NHS GMS → Mucolipidosis II and III Alpha or Beta · R289 NHS GMS → Rare syndromic craniosynostosis or isolated multisuture synostosis · R100 NHS GMS → Skeletal dysplasia · R104 NHS GMS → DDG2P NHS GMS → Intellectual disability NHS GMS →
NHS Genomic Medicine Service Jeen carrier screening

Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory

Frequently asked questions

What is the primary function of the GNPTAB gene?

The GNPTAB gene provides instructions for making subunits of the GlcNAc-1-phosphotransferase enzyme, which is crucial for tagging digestive enzymes with mannose-6-phosphate (M6P). This M6P tag directs these enzymes to lysosomes for breaking down waste materials within cells.

What conditions are associated with GNPTAB gene variants?

Variants in the GNPTAB gene are linked to mucolipidosis II (I-cell disease) and mucolipidosis III alpha/beta. Both are autosomal recessive lysosomal storage disorders characterised by an accumulation of unprocessed molecules within cells.

How do genetic variants in GNPTAB affect the body?

Genetic variants in GNPTAB disrupt the normal tagging and transport of lysosomal enzymes. Without proper enzyme delivery to lysosomes, waste products build up, leading to cellular dysfunction and a range of symptoms affecting multiple organ systems, characteristic of lysosomal storage disorders.

References

  1. Cathey SS, Leroy JG, Wood T. Phenotype and genotype in mucolipidoses II and III alpha/beta: a study of 61 probands. Journal of medical genetics. 2010. PMID: 19617216
  2. Otomo T, Muramatsu T, Yorifuji T. Mucolipidosis II and III alpha/beta: mutation analysis of 40 Japanese patients showed genotype-phenotype correlation. Journal of human genetics. 2009. PMID: 19197337
  3. Plante M, Claveau S, Lepage P. Mucolipidosis II: a single causal mutation in the N-acetylglucosamine-1-phosphotransferase gene (GNPTAB) in a French Canadian founder population. Clinical genetics. 2008. PMID: 18190596
  4. Braulke T, Pohl S, Storch S. Molecular analysis of the GlcNac-1-phosphotransferase. Journal of inherited metabolic disease. 2008. PMID: 18425436
  5. Kudo M, Brem MS, Canfield WM. Mucolipidosis II (I-cell disease) and mucolipidosis IIIA (classical pseudo-hurler polydystrophy) are caused by mutations in the GlcNAc-phosphotransferase alpha / beta -subunits precursor gene. American journal of human genetics. 2006. PMID: 16465621
  6. Bargal R, Zeigler M, Abu-Libdeh B. When Mucolipidosis III meets Mucolipidosis II: GNPTA gene mutations in 24 patients. Molecular genetics and metabolism. 2006. PMID: 16630736
  7. Steet RA, Hullin R, Kudo M. A splicing mutation in the alpha/beta GlcNAc-1-phosphotransferase gene results in an adult onset form of mucolipidosis III associated with sensory neuropathy and cardiomyopathy. American journal of medical genetics. Part A. 2005. PMID: 15633164
  8. Tiede S, Muschol N, Reutter G. Missense mutations in N-acetylglucosamine-1-phosphotransferase alpha/beta subunit gene in a patient with mucolipidosis III and a mild clinical phenotype. American journal of medical genetics. Part A. 2005. PMID: 16094673
  9. Tiede S, Storch S, Lübke T. Mucolipidosis II is caused by mutations in GNPTA encoding the alpha/beta GlcNAc-1-phosphotransferase. Nature medicine. 2005. PMID: 16200072
  10. Adam MP, Bick S, Mirzaa GM. GNPTAB-Related Disorders. 1993. PMID: 20301728
Educational content. This page is not medical or genetic advice, is not individually reviewed by a clinician for each reader, and should not replace a consultation with a qualified healthcare professional or genetic counsellor. If you are considering genetic testing or acting on a test result, book a consultation.
Data sources Last updated 11 October 2026. Content compiled from HGNC · MedlinePlus Genetics · ClinGen · Genomics England PanelApp · NHS National Genomic Test Directory · ClinVar · UniProt · AlphaFold .