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NDUFS2
NADH:ubiquinone oxidoreductase core subunit S2
NDUFS2 is located on the long (q) arm of chromosome 1, at band 1q23.3. Arm ratio per GRCh38 - banding schematic.
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Overview
NDUFS2 (NADH:ubiquinone oxidoreductase core subunit S2) encodes a critical structural and catalytic component of mitochondrial complex I, also known as NADH dehydrogenase. Complex I is the first and largest enzyme complex in the mitochondrial electron transport chain, responsible for initiating the process by which cells generate adenosine triphosphate (ATP), the primary energy currency of the cell. The NDUFS2 protein is essential for both the stability and enzymatic activity of the assembled complex. Pathogenic variants in NDUFS2 are inherited in an autosomal recessive pattern, meaning affected individuals carry two altered copies of the gene. These variants result in complex I deficiency, a form of mitochondrial disease that can affect multiple organ systems, particularly those with high energy demands such as the brain, heart, and skeletal muscle.
What the gene does
The NDUFS2 protein functions as a core subunit within the membrane arm of complex I, a large multi-subunit enzyme complex. Complex I catalyses the transfer of electrons from NADH (the reduced form of nicotinamide adenine dinucleotide) to ubiquinone (coenzyme Q10), coupling this reaction to the pumping of protons across the inner mitochondrial membrane. This proton gradient drives ATP synthesis by ATP synthase, the final step in oxidative phosphorylation. NDUFS2 contributes to the structural scaffold that supports the enzyme's catalytic machinery and helps maintain the integrity of the electron transfer pathway. The protein also participates in the assembly of complex I, a highly coordinated process involving numerous accessory factors. When NDUFS2 function is compromised, complex I activity drops substantially, reducing ATP production and increasing the generation of reactive oxygen species, which can damage cellular components including lipids, proteins, and nucleic acids.
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Chromosome location
NDUFS2 is located on the long arm of chromosome 1 at position 23.3, designated as 1q23.3. This chromosomal region contains multiple genes involved in fundamental cellular processes.
Protein structure
The NDUFS2 protein consists of 463 amino acids and is synthesised in the cytoplasm before being imported into mitochondria, where it undergoes processing and incorporation into the assembling complex I structure. The mature protein integrates into the membrane arm of the complex, contributing to both the structural framework and the functional electron transfer pathway.
Key variants
Pathogenic variants in NDUFS2 typically result in loss of protein function, either through reducing protein stability, impairing mitochondrial import, or disrupting incorporation into complex I. Missense variants that alter critical amino acids involved in subunit interactions or electron transfer are commonly reported, as are nonsense and frameshift variants that lead to premature termination of translation. The spectrum of variants includes both private mutations unique to individual families and recurrent changes observed across multiple unrelated patients.
Sample of pathogenic variants
5 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.1102C>T | p.Arg368Ter | Pathogenic | ★☆☆☆ | not provided |
c.128G>A | p.Trp43Ter | Pathogenic | ★☆☆☆ | not provided |
c.442G>A | p.Glu148Lys | Pathogenic | ★☆☆☆ | not provided |
c.686C>A | p.Pro229Gln | Pathogenic | - | Mitochondrial complex I deficiency, nuclear type 6 |
c.923A>G | p.Tyr308Cys | Pathogenic | - | Leber-like hereditary optic neuropathy, autosomal recessive 2 |
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
Biallelic pathogenic variants in NDUFS2 cause mitochondrial complex I deficiency, a severe metabolic disorder characterised by impaired cellular energy production. Clinical presentations vary considerably but often include neurological features such as developmental delay, seizures, hypotonia, and white matter abnormalities visible on brain imaging. Cardiomyopathy, affecting the heart muscle's ability to pump effectively, can also occur. Some affected individuals present in infancy with severe, rapidly progressive disease, whilst others may have a later onset with more variable symptoms. The severity and range of features depend on the degree of residual complex I activity and the specific tissues affected.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic NDUFS2 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
Within the UK NHS Genomic Medicine Service, NDUFS2 holds green (high-evidence) status across multiple clinical panels, reflecting strong evidence for its role in mitochondrial disease. The gene appears on the Mitochondrial disorders panel, the Mitochondrial disorder with complex I deficiency panel (R353), and the Inherited white matter disorders panel, amongst others. It is also included on the Paediatric or syndromic cardiomyopathy panel (R135) and the Likely inborn error of metabolism panel (R98), recognising the metabolic and cardiac manifestations that can occur. Additional memberships include the Possible mitochondrial disorder - nuclear genes panel (R63), the Undiagnosed metabolic disorders panel, and the White matter disorders and cerebral calcification - narrow panel, supporting diagnostic testing pathways for patients with suspected mitochondrial dysfunction.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
How is NDUFS2-related mitochondrial disease inherited?
NDUFS2-related mitochondrial disease follows an autosomal recessive inheritance pattern. An affected individual inherits one pathogenic variant from each parent, who are typically unaffected carriers. Each child of two carrier parents has a 25% chance of being affected, a 50% chance of being a carrier, and a 25% chance of inheriting two typical copies of the gene.
What is complex I deficiency?
Complex I deficiency is a mitochondrial disorder caused by impaired function of NADH dehydrogenase, the first enzyme complex in the electron transport chain. Reduced complex I activity leads to decreased ATP production and increased oxidative stress, affecting tissues with high energy requirements such as the brain, heart, and muscles.
Can carriers of NDUFS2 variants have symptoms?
Carriers of a single pathogenic NDUFS2 variant are generally unaffected and do not develop symptoms of mitochondrial disease. The condition requires two altered copies of the gene to manifest clinically.