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ST3GAL5 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

ST3GAL5 gene

The ST3GAL5 gene encodes an enzyme responsible for the first step in producing gangliosides, which are vital for nervous system development and function.

Normal Function

The ST3GAL5 gene provides instructions for making an enzyme called GM3 synthase. This enzyme carries out the first step in the production of gangliosides, which are fatty molecules (lipids) found on the surface of cells throughout the body, particularly in the nervous system. While their exact functions are complex, gangliosides help regulate chemical signaling pathways that influence cell growth, movement, adhesion, and survival, and are important for normal brain development.

Health Conditions Related to Genetic Changes

GM3 synthase deficiency

At least one mutation in the ST3GAL5 gene has been found to cause GM3 synthase deficiency, a condition characterized by recurrent seizures (epilepsy) and problems with brain development. The known mutation (Arg288Ter or R288X) prevents the production of any functional GM3 synthase. Without this enzyme, cells cannot produce GM3 or other gangliosides normally. Researchers are currently investigating whether the resulting signs and symptoms are caused by the lack of gangliosides, a buildup of the compounds used to make them, or a combination of both.

Frequently Asked Questions

Infants with GM3 synthase deficiency often show developmental delays within the first few months, such as delayed motor milestones (e.g., sitting, crawling) and poor muscle tone. Seizure activity may appear as early as 3–6 months of age, typically presenting as focal or generalized tonic‑clonic seizures that are difficult to control with standard antiepileptic drugs. Early neuroimaging may reveal mild brain atrophy or white‑matter changes, but these findings are not specific. Early recognition is critical for initiating supportive care and seizure management.
There is no cure that restores ganglioside synthesis, but seizure control can be attempted with a combination of antiepileptic drugs (AEDs) such as valproate, levetiracetam, or topiramate. Some patients benefit from ketogenic diet therapy, which may reduce seizure frequency. Early initiation of physical, occupational, and speech therapy can also improve developmental outcomes. Clinical trials investigating enzyme replacement or gene therapy are in preclinical stages and not yet available.
The diagnosis is confirmed by sequencing the ST3GAL5 gene from a blood or saliva sample. Targeted next‑generation sequencing panels for metabolic or epileptic encephalopathies often include ST3GAL5. If a pathogenic variant such as Arg288Ter (R288X) is identified, functional studies—like measuring ganglioside levels in cultured fibroblasts—can support the diagnosis. A negative result does not rule out the disorder, so clinical correlation and repeat testing may be necessary.
ST3GAL5 mutations are inherited in an autosomal recessive pattern. If both parents are carriers, each pregnancy has a 25 % chance of producing an affected child, a 50 % chance of a carrier child, and a 25 % chance of a child who is neither carrier nor affected. Prenatal testing via chorionic villus sampling (CVS) or amniocentesis can identify affected fetuses. Pre‑implantation genetic diagnosis (PGD) with in‑vitro fertilization (IVF) is another option to avoid affected pregnancies. Genetic counseling should discuss recurrence risks, testing options, and family planning strategies.
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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