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COX15
cytochrome c oxidase assembly factor COX15
The *COX15* gene provides instructions for a protein essential in the assembly of cytochrome *c* oxidase, a vital enzyme within the mitochondria responsible for cellular energy production. The *COX15* gene plays a critical role in mitochondrial function by encoding a protein involved in the final steps of assembling cytochrome *c* oxidase (Complex IV).
COX15 is located on the long (q) arm of chromosome 10, at band 10q24.2. Arm ratio per GRCh38 - banding schematic.
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Overview
The *COX15* gene, also known as cytochrome *c* oxidase assembly factor COX15, is fundamental for proper mitochondrial function. It provides genetic instructions for a protein that is crucially involved in the creation of cytochrome *c* oxidase, or Complex IV, which is a major component of the electron transport chain within mitochondria.
Dysfunction of the *COX15* gene can disrupt this essential energy-producing pathway, leading to severe inherited metabolic conditions. These conditions often manifest as mitochondrial disorders, impacting various organ systems due to insufficient cellular energy.
What the gene does
The protein encoded by the *COX15* gene is located in the inner mitochondrial membrane and is a key player in the biogenesis of cytochrome *c* oxidase (COX), also known as Complex IV. COX is the final enzyme complex in the mitochondrial electron transport chain, performing the oxygen-dependent step of cellular respiration.
Specifically, the COX15 protein is involved in the synthesis of heme A, a vital cofactor integrated into Complex IV. Heme A is created through a series of enzymatic modifications within the mitochondria, and COX15 facilitates the final oxygenation step in this pathway. Without sufficient and functional heme A, Complex IV cannot be properly assembled or maintain its structural integrity and catalytic activity, which impairs energy production and consequently affects cellular health.
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Chromosome location
The *COX15* gene is found on chromosome 10, specifically at position 10q24.2. This genomic location refers to the long (q) arm of chromosome 10, within region 2, band 4, and sub-band 2.
Protein structure
The COX15 protein consists of 410 amino acids. Domain architecture has not been experimentally characterised in detail for this protein.
Key variants
Variants in the *COX15* gene can lead to a spectrum of mitochondrial disorders. These genetic changes are typically inherited in an autosomal recessive manner, meaning an individual must inherit two copies of the altered gene (one from each parent) to develop the condition. Variants range from single nucleotide changes to larger deletions or insertions, all potentially impacting the protein's ability to facilitate heme A synthesis and Complex IV assembly.
Sample of pathogenic variants
10 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.272+2T>G | - | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.281_282del | p.Glu94fs | Pathogenic | ★★☆☆ | not provided |
c.305G>A | p.Trp102Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Leigh syndrome |
c.452C>G | p.Ser151Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Leigh syndrome |
c.457C>T | p.Arg153Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Cardioencephalomyopathy, fatal infantile, due to cytochrome c oxidase deficiency 2 |
c.597G>A | p.Trp199Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Cardioencephalomyopathy, fatal infantile, due to cytochrome c oxidase deficiency 2 |
c.649C>T | p.Arg217Trp | Pathogenic | ★★☆☆ | COX15-related disorder |
c.686C>A | p.Ser229Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Cardioencephalomyopathy, fatal infantile, due to cytochrome c oxidase deficiency 2 |
c.717G>A | p.Trp239Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Cardioencephalomyopathy, fatal infantile, due to cytochrome c oxidase deficiency 2 |
c.830C>G | p.Ser277Ter | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
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
Pathogenic variants in the *COX15* gene are associated with mitochondrial disorders, primarily characterised by a deficiency in cytochrome *c* oxidase (Complex IV). These conditions can present with a wide array of symptoms affecting multiple body systems, including neurological dysfunction, developmental delays, movement disorders, and cardiomyopathy. The severity and presentation can vary significantly between individuals.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic COX15 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
In the UK, the *COX15* gene is recognised on several NHS Genomic Medicine Service national test panels. These include panels for Childhood onset dystonia, chorea or related movement disorder, DDG2P, Inherited white matter disorders, Intellectual disability, Likely inborn error of metabolism, Mitochondrial disorders, Mitochondrial disorder with complex IV deficiency, Paediatric or syndromic cardiomyopathy, Possible mitochondrial disorder - nuclear genes, Structural basal ganglia disorders, and Undiagnosed metabolic disorders, and White matter disorders and cerebral calcification - narrow panel. This indicates its clinical relevance in diagnosing a range of neurological and metabolic conditions within the NHS.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the primary function of the COX15 gene?
The *COX15* gene provides instructions for a protein that is essential for the assembly of cytochrome *c* oxidase (Complex IV), a crucial enzyme in the mitochondria's electron transport chain responsible for cellular energy production.
How are conditions associated with COX15 typically inherited?
Conditions linked to pathogenic variants in the *COX15* gene are generally inherited in an autosomal recessive manner. This means an individual must inherit two altered copies of the gene, one from each parent, to be affected.
What kind of health issues can arise from COX15 gene variants?
Pathogenic *COX15* variants can lead to mitochondrial disorders, often characterised by cytochrome *c* oxidase deficiency. These disorders can cause diverse symptoms affecting neurological development, movement, and heart function due to impaired cellular energy metabolism.