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GNPTG gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

GNPTG gene

The GNPTG gene provides instructions for the gamma subunit of an enzyme essential for directing digestive enzymes to the correct cellular compartments.

Normal Function

The GNPTG gene provides instructions for making the gamma (γ) subunit of an enzyme called GlcNAc-1-phosphotransferase. This enzyme is made up of two alpha (α), two beta (β), and two gamma (γ) subunits. The alpha and beta subunits are produced by a different gene, GNPTAB. GlcNAc-1-phosphotransferase helps prepare newly made enzymes for transport to lysosomes, which are compartments within the cell that use digestive enzymes called hydrolases to break down large molecules.

The enzyme is involved in the first step of creating a molecule called mannose-6-phosphate (M6P). M6P acts as a tag that indicates a hydrolase should be transported to the lysosome. GlcNAc-1-phosphotransferase transfers a molecule called GlcNAc-1-phosphate to a newly produced hydrolase. Once the M6P tag is revealed, the hydrolase can be successfully transported to the lysosome.

Health Conditions Related to Genetic Changes

Mucolipidosis III gamma

At least 8 mutations in the GNPTG gene have been found to cause mucolipidosis III gamma. These mutations reduce the activity of GlcNAc-1-phosphotransferase, disrupting the tagging of hydrolases with M6P. Digestive enzymes that do not receive the M6P tag end up outside the cell, where they have increased activity. The resulting shortage of these enzymes within lysosomes causes large molecules to accumulate, which is why this condition is classified as a lysosomal storage disorder.

Other Names for This Gene

  • C16orf27
  • c316G12.3
  • CAB56184
  • GlcNAc-phosphotransferase gamma-subunit
  • GNPTAG
  • GNPTG_HUMAN
  • LP2537
  • N-acetylglucosamine-1-phosphate transferase gamma subunit
  • N-acetylglucosamine-1-phosphate transferase, gamma subunit
  • N-acetylglucosamine-1-phosphotransferase, gamma subunit
  • RJD9

Frequently Asked Questions

No enzyme‑replacement therapy is approved for mucolipidosis III γ. Treatment is supportive: regular orthopedic evaluation, physiotherapy for joint range‑of‑motion, and management of respiratory infections. Clinical trials of substrate‑reduction or gene‑therapy approaches are ongoing but not yet available clinically.
GNPTG encodes the gamma subunit of GlcNAc‑1‑phosphotransferase; loss‑of‑function mutations reduce enzyme activity, leading to incomplete tagging of lysosomal hydrolases. Compared with GNPTAB‑related forms, mucolipidosis III γ often presents later (preschool age), with milder skeletal abnormalities, less severe growth retardation, and predominantly joint stiffness and mild facial coarseness.
Targeted sequencing of the GNPTG gene (single‑gene panel) or inclusion of GNPTG in a broader lysosomal storage disorder panel can detect pathogenic variants. If initial testing is negative but suspicion remains, whole‑exome or whole‑genome sequencing can be employed.
Since GNPTG disease is autosomal recessive, carrier testing of both parents confirms carrier status. If both are carriers, each future pregnancy carries a 25 % risk of an affected child. Options include preimplantation genetic testing, prenatal diagnostic testing (chorionic villus sampling or amniocentesis), or use of donor gametes. Genetic counseling is recommended to discuss these choices.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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