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SURF1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

SURF1 gene

The SURF1 gene encodes a protein essential for assembling complex IV of the mitochondrial electron transport chain, and mutations can lead to severe disorders such as Leigh syndrome. Understanding its function and associated conditions helps guide diagnosis and research.

Normal Function

The SURF1 gene provides instructions for making a protein that is important in oxidative phosphorylation, the process by which the energy from food is converted into a form cells can use. Oxidative phosphorylation involves a series of reactions that take place through several different protein complexes. The SURF1 protein aids in the correct assembly of one of the protein complexes, or enzymes, involved in oxidative phosphorylation called complex IV.

Complex IV, also known as cytochrome c oxidase or COX, accepts negatively charged particles (electrons) from earlier steps in oxidative phosphorylation. In addition, the enzyme accepts positively charged particles (protons) from inside the mitochondrion. Using the electrons and protons, the COX enzyme performs a chemical reaction that converts oxygen to water. The enzyme also transfers additional protons across the specialized membrane inside the mitochondrion. These processes create energy that is used to generate adenosine triphosphate (ATP), the cell's main energy source.

Health Conditions Related to Genetic Changes

Charcot-Marie-Tooth disease

MedlinePlus Genetics provides information about Charcot-Marie-Tooth disease

More About This Health Condition

Cytochrome c oxidase deficiency

MedlinePlus Genetics provides information about Cytochrome c oxidase deficiency

More About This Health Condition

Leigh syndrome

More than 80 different SURF1 gene mutations have been identified in people with Leigh syndrome, a progressive brain disorder that usually appears in infancy or early childhood. Affected children may experience delayed development, muscle weakness, problems with movement, or difficulty breathing.

Approximately 10 to 15 percent of people with Leigh syndrome have a mutation in the SURF1 gene. Most SURF1 gene mutations result in an abnormally short protein. Other mutations replace a single protein building block in the SURF1 protein. The mutated proteins are broken down in the cell, which results in the absence of SURF1

Frequently Asked Questions

The diagnostic work‑up includes a brain MRI showing symmetrical lesions in the basal ganglia, thalami, or brainstem; a muscle biopsy with histochemical staining for cytochrome c oxidase (COX) activity; and a respiratory chain enzyme assay that often shows reduced complex IV activity. Genetic testing—preferably a targeted mitochondrial disease panel or whole‑exome sequencing—identifies pathogenic SURF1 variants. A normal COX activity in blood lymphocytes does not rule out the disease, so muscle tissue is preferred.
No curative therapy exists, but supportive care improves quality of life. High‑dose thiamine (vitamin B1) and coenzyme Q10 supplementation are sometimes trialed, though evidence is limited. Antiepileptic drugs tailored to seizure type, physiotherapy to maintain motor function, and respiratory support (e.g., non‑invasive ventilation) are standard. Early referral to a multidisciplinary mitochondrial clinic can coordinate care and monitor for complications such as cardiomyopathy or hearing loss.
SURF1 is essential for assembling complex IV of the mitochondrial electron transport chain. When SURF1 is defective, complex IV assembly is impaired, reducing ATP production and increasing reactive oxygen species. Neurons, especially in the brainstem and basal ganglia, are highly energy‑dependent; their dysfunction manifests as developmental delay, hypotonia, ataxia, respiratory difficulties, and characteristic MRI findings such as bilateral basal ganglia lesions. The severity depends on the specific mutation and residual enzyme activity.
While SURF1 mutations are most commonly associated with Leigh syndrome, rare reports link them to axonal Charcot‑Marie‑Tooth (CMT) type 2. Clinically, CMT presents with distal muscle weakness, sensory loss, and foot deformities, whereas Leigh syndrome involves central nervous system signs, seizures, and respiratory failure. Electrophysiological studies (nerve conduction velocity) and MRI findings help differentiate. Genetic testing confirming a SURF1 variant in the context of CMT features warrants further evaluation for mitochondrial dysfunction, but the presence of typical Leigh syndrome MRI lesions strongly suggests a Leigh phenotype.
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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