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COG7
component of oligomeric golgi complex 7
COG7 is located on the short (p) arm of chromosome 16, at band 16p12.2. Arm ratio per GRCh38 - banding schematic.
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Overview
COG7 is located on chromosome 16 and encodes a 770-amino-acid protein that forms part of the conserved oligomeric Golgi (COG) complex. This complex acts as a tethering factor, ensuring that transport vesicles carrying glycosylation enzymes and other cargo are correctly targeted within the Golgi apparatus. When COG7 function is disrupted, cells cannot maintain the organised structure of the Golgi or properly modify proteins with sugar chains, leading to widespread cellular dysfunction.
Biallelic pathogenic variants in COG7 cause a congenital disorder of glycosylation, an inherited metabolic condition that affects multiple organ systems. Because glycosylation is essential for the normal function of proteins throughout the body, loss of COG7 activity typically results in developmental delays, liver dysfunction, and neurological features. The condition follows an autosomal recessive inheritance pattern, meaning that two altered copies of the gene must be present for symptoms to develop.
What the gene does
The COG7 protein serves as one of eight subunits within the COG complex, which orchestrates retrograde trafficking of Golgi-resident proteins. The Golgi apparatus is a cellular sorting centre where newly synthesised proteins receive modifications, particularly the addition of complex carbohydrate structures through glycosylation. COG7 and its partner subunits form a scaffold that captures transport vesicles returning from later Golgi compartments and tethers them to earlier cisternae, ensuring that glycosylation enzymes remain in their correct locations.
Without functional COG7, the spatial organisation of glycosylation machinery breaks down. Enzymes responsible for adding specific sugar residues to proteins become mislocalised, disrupting the sequential assembly of glycan chains. This leads to underglycosylation or misglycosylation of numerous cellular and secreted proteins, impairing their stability and function. The effects are particularly pronounced in rapidly developing tissues and organs with high metabolic demands, including the liver, brain, and skeletal system, where proper protein glycosylation is critical for normal growth and cellular homeostasis.
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Chromosome location
COG7 is located on the short arm of chromosome 16 at band 16p12.2. This chromosomal region contains several genes involved in developmental and metabolic processes. The precise genomic coordinates and exon structure of COG7 have been mapped through reference genome assemblies, enabling targeted sequencing approaches for diagnostic testing.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein. The COG7 polypeptide chain comprises 770 amino acids and interacts with other COG subunits to form the functional octameric complex. Structural studies of the broader COG assembly suggest that individual subunits contribute distinct interaction surfaces that allow the complex to bind both vesicle coat proteins and Golgi membrane components, though the precise molecular interfaces involving COG7 remain under investigation.
Key variants
Pathogenic variants in COG7 are rare and typically include loss-of-function changes such as nonsense mutations, frameshift deletions, and splice-site alterations that disrupt normal protein production. Missense substitutions affecting conserved residues critical for subunit interactions or complex stability have also been reported. Because the condition follows autosomal recessive inheritance, affected individuals carry biallelic variants, whilst heterozygous carriers generally remain asymptomatic.
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.1330C>T | p.Arg444Ter | Pathogenic/Likely pathogenic | ★★☆☆ | COG7 congenital disorder of glycosylation |
c.1817C>A | p.Ala606Asp | Pathogenic/Likely pathogenic | ★★☆☆ | COG7 congenital disorder of glycosylation |
c.323dup | p.Leu108fs | Pathogenic | ★★☆☆ | COG7 congenital disorder of glycosylation |
g.(?_23417377)_(23417603_?)del | - | Pathogenic | ★☆☆☆ | COG7 congenital disorder of glycosylation |
c.1673C>A | p.Ser558Ter | Pathogenic | ★☆☆☆ | COG7 congenital disorder of glycosylation |
c.1702C>T | p.Arg568Ter | Pathogenic | ★☆☆☆ | COG7 congenital disorder of glycosylation |
c.1808G>A | p.Trp603Ter | Pathogenic | ★☆☆☆ | COG7 congenital disorder of glycosylation |
c.1999C>T | p.Gln667Ter | Pathogenic | ★☆☆☆ | COG7 congenital disorder of glycosylation |
c.343_344insTCCCTCTCCCTCTCCCGTCTCCCTCTCCCTCTCCCGTCTCCCGCTCCCTCTCCCGGCTCCCGCTCCCGCTCCCGGGGCCCTCTCCCGCGCGCGGCNNNNNNNNNNAAAAAAAAAAAAAAAAAAAAAGAAATTGACCAAGTGA | p.Lys115delinsIleProLeuProLeuProSerProSerProSerProValSerArgSerLeuSerArgLeuProLeuProLeuProGlyProSerProAlaArgGlyXaaXaaXaaXaaLysLysLysLysLysLysArgAsnTer | Pathogenic | ★☆☆☆ | COG7 congenital disorder of glycosylation |
c.669C>A | p.Tyr223Ter | Pathogenic | ★☆☆☆ | COG7 congenital disorder of glycosylation |
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 COG7 result in COG7-congenital disorder of glycosylation (COG7-CDG), a rare inherited metabolic condition characterised by abnormal protein glycosylation. Clinical features typically include developmental delay, intellectual disability, seizures, liver dysfunction with cholestasis, skeletal abnormalities, and failure to thrive. The severity and specific manifestations can vary among affected individuals, reflecting the widespread importance of glycosylation across organ systems. Early diagnosis through biochemical testing and genetic analysis enables supportive care and monitoring for complications.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic COG7 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
COG7 is included on multiple NHS Genomic Medicine Service gene panels, reflecting its relevance to various clinical presentations. The gene holds green (high evidence) status on panels including Cholestasis, Congenital Disorders of Glycosylation, Early Onset or Syndromic Epilepsy, Fetal Anomalies, Intellectual Disability, Likely Inborn Error of Metabolism, Neonatal Cholestasis, and Undiagnosed Metabolic Disorders. This broad panel representation reflects the multi-system nature of COG7-related disease and supports testing in individuals presenting with combinations of liver, neurological, and developmental features.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does it mean to be a carrier of a COG7 variant?
Carriers have one altered copy of COG7 and one working copy, which is generally sufficient for normal Golgi function and protein glycosylation. Carriers typically have no symptoms but can pass the variant to their children.
How is COG7-related disease diagnosed?
Diagnosis often begins with clinical suspicion based on symptoms such as developmental delay, liver dysfunction, and neurological features. Biochemical testing may reveal abnormal glycosylation patterns, and genetic testing confirms the presence of biallelic COG7 variants.
Can COG7 variants cause problems detectable before birth?
Some individuals with COG7-related conditions may have foetal anomalies detectable on antenatal imaging, which is why the gene appears on the NHS Fetal Anomalies panel. However, the specific findings vary and not all affected pregnancies show antenatal abnormalities.