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COA7
cytochrome c oxidase assembly factor 7
COA7 is located on the short (p) arm of chromosome 1, at band 1p32.3. Arm ratio per GRCh38 - banding schematic.
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Overview
COA7 (cytochrome c oxidase assembly factor 7) is located on chromosome 1 at position 1p32.3 and consists of coding sequence that produces a 231-amino acid protein. The COA7 protein functions within mitochondria to coordinate the assembly of cytochrome c oxidase, also known as mitochondrial respiratory chain complex IV. This enzyme complex transfers electrons to oxygen during cellular respiration, a process fundamental to energy metabolism in human cells. When COA7 function is disrupted through genetic variation, cells experience deficiencies in complex IV activity, leading to impaired energy production that particularly affects tissues with high metabolic demands such as the brain, muscles, and peripheral nerves.
What the gene does
The COA7 protein operates as a specialised assembly factor that coordinates the construction of cytochrome c oxidase within the inner mitochondrial membrane. Cytochrome c oxidase comprises multiple protein subunits encoded by both mitochondrial and nuclear DNA, and its assembly requires a carefully orchestrated series of steps involving numerous helper proteins. COA7 facilitates the incorporation of copper cofactors into specific subunits of the complex, a process essential for the enzyme's electron transfer activity. The protein appears to interact with other assembly factors and newly synthesised complex IV subunits during intermediate stages of construction. By ensuring proper metalation and structural organisation, COA7 enables the formation of functional cytochrome c oxidase complexes capable of sustaining the final step of the electron transport chain. Without adequate COA7 function, complex IV assembly stalls, leading to reduced enzyme activity and compromised cellular respiration, particularly affecting organs with high energy requirements.
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Chromosome location
The COA7 gene is positioned on the short arm of chromosome 1 at cytogenetic band 1p32.3. This chromosomal region contains multiple genes involved in various cellular processes. The genomic structure of COA7 and its regulatory elements direct tissue-specific expression patterns that ensure adequate protein levels in metabolically active tissues.
Protein structure
The COA7 protein contains a series of five Sel1-like repeats that form its characteristic structural architecture. These repeats span Sel1-like 1 (amino acids 34-66), Sel1-like 2 (amino acids 68-104), Sel1-like 3 (amino acids 108-146), Sel1-like 4 (amino acids 147-183), and Sel1-like 5 (amino acids 184-219). Sel1-like repeat domains are known to mediate protein-protein interactions, and in COA7 these repeats likely facilitate binding to other assembly factors and cytochrome c oxidase subunits during complex IV biogenesis. The arrangement of these tandem repeats creates a scaffold structure that positions the protein appropriately within the mitochondrial assembly machinery.
Key variants
Genetic variants in COA7 that disrupt protein function typically result in reduced or absent assembly factor activity. Pathogenic changes include missense variants that alter critical amino acids within the Sel1-like repeats, frameshift or nonsense variants that truncate the protein, and variants affecting splice sites that lead to aberrant transcript processing. The spectrum of variants reflects different degrees of functional impairment, contributing to variable clinical presentations in affected individuals.
Sample of pathogenic variants
2 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.17A>G | p.Asp6Gly | Pathogenic | - | Spinocerebellar ataxia, autosomal recessive, with axonal neuropathy 3 |
c.247+1G>T | - | Pathogenic | - | Spinocerebellar ataxia, autosomal recessive, with axonal neuropathy 3 |
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 COA7 cause mitochondrial complex IV deficiency, a disorder characterised by impaired cellular energy production. Clinical manifestations vary but often include neurological features such as ataxia (impaired coordination), peripheral neuropathy (nerve damage affecting sensation and movement), and developmental delay. Some affected individuals present with multisystem involvement affecting the brain, muscles, and other metabolically demanding organs. The severity and specific features depend on the degree of residual complex IV activity and the tissues most vulnerable to energy deficits.
No disease links recorded for this gene in our reference set.
UK clinical status
Within the NHS Genomic Medicine Service, COA7 holds green (diagnostic-grade) classification across multiple clinical panels reflecting its recognised role in mitochondrial and neurological disorders. The gene appears on the Mitochondrial disorders panel, Mitochondrial disorder with complex IV deficiency panel, and Possible mitochondrial disorder - nuclear genes panel, supporting its use in diagnosing energy metabolism conditions. COA7 is also included on panels for Hereditary ataxia with onset in adulthood, Hereditary neuropathy, Ataxia and cerebellar anomalies, and White matter disorders and cerebral calcification, reflecting the neurological presentations associated with complex IV deficiency. Additional memberships on the Likely inborn error of metabolism and Fetal anomalies panels acknowledge the broad spectrum of metabolic and developmental presentations.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the COA7 gene do?
The COA7 gene encodes a mitochondrial assembly factor that helps construct cytochrome c oxidase, the enzyme complex responsible for the final step in cellular energy production. The protein coordinates the incorporation of copper cofactors and ensures proper assembly of the complex within mitochondria.
How do COA7 variants affect health?
Pathogenic variants in COA7 impair the assembly of cytochrome c oxidase, leading to complex IV deficiency and reduced cellular energy production. This results in clinical features including ataxia, peripheral neuropathy, developmental delay, and other neurological or multisystem manifestations depending on the severity of the deficiency.
Is COA7 tested in the NHS?
Yes, COA7 is included on multiple NHS Genomic Medicine Service panels with green (diagnostic-grade) status, including panels for mitochondrial disorders, hereditary ataxia, hereditary neuropathy, and inborn errors of metabolism, reflecting its established role in diagnosing complex IV deficiency.