rs587776949 — NDUFS4

Frameshift deletion in NDUFS4 abolishing mitochondrial complex I function; homozygous carriers develop Leigh syndrome, a severe infantile encephalopathy; heterozygous carriers are unaffected but carry a reproductive risk, particularly in Ashkenazi Jewish families

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NDUFS4 c.462delA — A Mitochondrial Complex I Frameshift with Leigh Syndrome Risk

Mitochondrial complex I (NADH:ubiquinone oxidoreductase11 NADH:ubiquinone oxidoreductase
The largest enzyme in the mitochondrial respiratory chain, comprising 45 subunits, 14 of which form the catalytic core. It transfers electrons from NADH to ubiquinone, pumping protons to drive ATP synthesis) is the cell's primary engine for converting food into energy. The NDUFS4 subunit is a nuclear-encoded accessory subunit22 nuclear-encoded accessory subunit
NDUFS4 is encoded in the nuclear genome and imported into the mitochondrial matrix; it stabilizes the final assembly of the complex I holocomplex and carries a cAMP-dependent phosphorylation site that regulates enzyme activation required for complete complex I assembly and activation. The c.462delA frameshift — a single adenine deletion at position 462 in the coding sequence — disrupts the reading frame at codon 154, producing a truncated protein (p.Lys154fs) that lacks the phosphorylation site essential for complex I activation.

Among Ashkenazi Jewish families, this variant has been identified as a founder mutation33 founder mutation
A mutation present in high frequency in a specific population due to descent from a small number of founders who carried the variant; the AJ population has experienced several well-characterized founder effects for recessive disease alleles with a carrier frequency of approximately 1 in 1,000. For most carriers, the other copy of NDUFS4 is intact and complex I function is entirely normal. The risk materializes only when both parents are carriers, giving each child a 25% chance of inheriting two deletion alleles and developing Leigh syndrome.

The Mechanism

The c.462delA deletion shifts the reading frame after codon 154, replacing the final 22 amino acids of NDUFS4 with a novel sequence before encountering a premature stop codon. The resulting truncated protein cannot serve its normal role in complex I holocomplex stabilization44 complex I holocomplex stabilization
NDUFS4 is incorporated in one of the last steps of complex I assembly. Without functional NDUFS4, the 550-kilodalton membrane-arm complex assembles but remains unstable and is present at sharply reduced levels. The critical phosphorylation site for cAMP-dependent kinase activation is also absent, further impairing the enzyme's ability to respond to cellular energy signals.

Homozygous loss of NDUFS4 therefore creates a state of severe mitochondrial energy deficiency. Neurons — which depend almost entirely on oxidative phosphorylation — are the most vulnerable cell type. In the Ndufs4 knockout mouse model, glutamatergic neurons mediate most of the motor and respiratory phenotype55 glutamatergic neurons mediate most of the motor and respiratory phenotype
Single-cell studies show Vglut2-expressing glutamatergic neurons in the brainstem die earliest; GABAergic neurons contribute later through inflammation and epilepsy, while activated microglia drive a secondary neuroinflammatory cascade involving NLRP3 inflammasome and IL-666 NLRP3 inflammasome and IL-6
Elevated NLRP3 and IL-6 pro-inflammatory pathways were confirmed in NDUFS4-mutant iPSC-derived brain organoids and postmortem Leigh syndrome tissue from human patients that amplifies neuronal death.

The Evidence

The clinical significance of biallelic NDUFS4 loss is unambiguous. Leigh syndrome (subacute necrotizing encephalomyelopathy) caused by NDUFS4 mutations presents in infancy or early childhood with developmental regression, hypotonia, feeding difficulties, respiratory failure, and characteristic bilateral symmetric lesions in the basal ganglia and brainstem on MRI. The course is typically progressive and often fatal within the first years of life77 often fatal within the first years of life
Published case series document death from respiratory failure, usually before age 5, in most NDUFS4-null children; some survive longer with intensive supportive care.

Anderson et al. 200888 Anderson et al. 2008
Journal of Inherited Metabolic Disease, December 2008 (PMID 19107570) identified c.462delA as the causal mutation in three affected children from a non-consanguineous Ashkenazi Jewish family. Screening of 5,000 healthy AJ individuals revealed a carrier frequency of approximately 1 in 1,000, leading the authors to recommend that this variant should be evaluated in all AJ patients presenting with Leigh syndrome before proceeding to more extensive enzyme studies.

Leshinsky-Silver et al. 200999 Leshinsky-Silver et al. 2009
Molecular Genetics and Metabolism, July 2009 (PMID 19364667) confirmed p.Lys154fs in a second patient — a compound heterozygote carrying the AJ founder allele alongside a novel NDUFS4 missense — with Leigh syndrome showing predominant brainstem involvement and fatal outcome in early childhood. Together these reports establish the biological mechanism, the Ashkenazi Jewish population risk, and the clinical phenotype.

Practical Actions

For confirmed carriers (DI genotype), the finding has no impact on personal health — complex I activity is entirely normal with one functional allele. The clinical relevance is reproductive: if a carrier has a child with a partner who is also a carrier, each pregnancy has a 25% risk of Leigh syndrome.

Carrier screening for the Ashkenazi Jewish population panel should include NDUFS4 c.462delA. Several expanded carrier screening programs include it explicitly. For carriers planning a family, preconception genetic counseling can guide decisions about preimplantation genetic testing (PGT) or prenatal diagnosis.

For the rare homozygous individual, management is supportive and ideally coordinated by a specialized mitochondrial disease center. Treatments under investigation in animal models include rapamycin (mTOR inhibition to reduce cellular energy demand) and ketogenic diet (providing an alternative fuel source that bypasses the complex I block). Microglial ablation has extended lifespan in mouse models by reducing neuroinflammation. None of these are established clinical protocols, but referral to a mitochondrial disease specialist ensures access to current evidence and any available clinical trials.

Interactions

As an autosomal recessive condition, the key interaction is the combination of two heterozygous NDUFS4 c.462delA carriers producing a homozygous child. This is documented as a Mendelian transmission pattern, not a genetic interaction in the complex-I-pathway sense. There are no documented gene-gene interactions between NDUFS4 c.462delA and other nuclear-encoded complex I subunit variants in terms of modifying carrier status — two heterozygous carriers of different NDUFS4 pathogenic alleles could produce a compound heterozygous affected child, which is biologically equivalent to homozygosity in terms of complex I loss.

Genotype Interpretations

What each possible genotype means for this variant.

II Non-carrier Normal

No NDUFS4 deletion detected; normal mitochondrial complex I function

You do not carry the c.462delA frameshift deletion in NDUFS4. Your mitochondrial complex I is expected to assemble and function normally. This variant is very rare globally — it is found primarily in Ashkenazi Jewish families at a carrier frequency of roughly 1 in 1,000. The vast majority of people worldwide are non-carriers.

DI Carrier Carrier

Single-copy NDUFS4 deletion carrier — no personal health impact, reproductive consideration

The NDUFS4 gene follows strict autosomal recessive inheritance — two non-functional copies are needed to cause disease. As a heterozygous carrier, your single intact allele provides enough NDUFS4 protein for normal complex I assembly and energy metabolism. Long-term health outcomes for carriers are indistinguishable from non-carriers.

The c.462delA allele is a recognized founder mutation in the Ashkenazi Jewish population. Anderson et al. 2008 (PMID 19107570) identified it in three affected children from a non-consanguineous AJ family and confirmed a carrier frequency of ~1/1,000 in 5,000 healthy AJ individuals. This makes it relevant to population-level carrier screening programs for Ashkenazi Jewish couples planning pregnancies.

If you are of Ashkenazi Jewish descent and planning a family, partner testing is the critical next step. If both partners carry the deletion, preimplantation genetic testing (PGT-M) or prenatal diagnosis (chorionic villus sampling or amniocentesis) can determine whether a pregnancy is affected.

DD Homozygous Homozygous

Two copies of NDUFS4 deletion — associated with mitochondrial complex I deficiency and Leigh syndrome

Homozygosity for NDUFS4 c.462delA produces a truncated protein (p.Lys154fs) that cannot fulfill its role in the final stabilization steps of complex I assembly. The result is a severely reduced, unstable complex I holocomplex with profoundly impaired electron transfer from NADH to ubiquinone. Neurons are the most vulnerable cell type because they rely almost exclusively on oxidative phosphorylation for ATP production.

In published case series, affected children present in infancy or early childhood (median onset before 2 years) with the hallmarks of Leigh syndrome: developmental plateau followed by regression, hypotonia, feeding difficulties, and recurrent metabolic crises triggered by illness. Brain MRI shows bilateral symmetric hyperintense lesions in the basal ganglia, brainstem, and cerebellum. Respiratory failure, caused by brainstem involvement, is the leading cause of death. Most children with NDUFS4-null Leigh syndrome do not survive beyond early childhood, though clinical severity varies and some patients have longer courses.

Management is supportive — there is no approved curative therapy. Research in Ndufs4 knockout mice has identified mTOR inhibition (rapamycin) and ketogenic diet as interventions that extend lifespan in animal models, and these approaches are being evaluated in clinical settings. Specialized mitochondrial disease centers offer the most comprehensive supportive care and access to clinical trials.

Because this genotype is typically identified through genetic evaluation of a symptomatic child, this entry is primarily relevant for confirming an established or suspected diagnosis, for reproductive planning in affected families, and for cascade testing of relatives.