On this page
CNGA1
cyclic nucleotide gated channel subunit alpha 1
The *CNGA1* gene provides instructions for making a protein subunit essential for the function of cyclic nucleotide-gated ion channels, which play a crucial role in the visual process. The *CNGA1* gene is vital for the proper function of photoreceptor cells in the retina.
CNGA1 is located on the short (p) arm of chromosome 4, at band 4p12. Arm ratio per GRCh38 - banding schematic.
Explore chromosome 4 in the library →Available at Jeen Health
Clinical tests that include this
Overview
The *CNGA1* gene, full name cyclic nucleotide-gated channel subunit alpha 1, is located on chromosome 4. It codes for a protein that forms part of a crucial ion channel in the eye's retina. This channel is integral to phototransduction, the process by which light is converted into electrical signals for the brain.
Changes within the *CNGA1* gene can disrupt this process, leading to various inherited retinal disorders. Jeen Health categorises *CNGA1* as Tier 2-3 for actionability, indicating its established role in genetic conditions, particularly within ophthalmology.
What the gene does
The protein produced by the *CNGA1* gene is a subunit of a cyclic nucleotide-gated (CNG) ion channel. These channels are paramount in retinal photoreceptor cells, where they open in response to cyclic GMP (cGMP), an intracellular messenger activated by light. This opening allows ions such as sodium and calcium to flow into the cell, initiating the electrical signal that the brain interprets as vision.
Specifically, the CNGA1 protein forms part of the pore through which these ions pass, regulating the sensitivity and speed of the visual response. Its correct function is indispensable for the initial steps of light perception. The ion conduction pathway and selectivity filter regions of the protein are directly involved in controlling this ion flow.
Video: Genetics 101
Chromosome location
The *CNGA1* gene is found on chromosome 4, specifically at position 4p12. This location refers to the short (p) arm of chromosome 4, within band 12. Its precise genomic position helps delineate its neighbourhood with other genes and can be significant for genetic studies and mapping.
Protein structure
The CNGA1 protein is composed of 686 amino acids and exhibits several key functional regions. Notably, it contains two Disordered regions, at amino acids 31-75 and 87-149, which often play roles in protein-protein interactions or regulatory mechanisms. The Ion conduction pathway, spanning amino acids 291-399, is central to its function as an ion channel, with a critical Selectivity filter at amino acids 358-361 that determines which ions can pass through.
Further structural elements include the C-linker (amino acids 401-477), vital for coupling the cyclic nucleotide-binding domain to the channel pore, and the Cyclic nucleotide-binding domain itself (amino acids 481-601), which is responsible for binding cGMP. A Coiled coil region is also present from amino acids 619-673, which may contribute to protein stability or subunit assembly.
Key variants
Variants in the *CNGA1* gene can range from single base changes to larger deletions or insertions within the gene sequence. These genetic differences can alter the structure or function of the CNGA1 protein, potentially impairing the cyclic nucleotide-gated ion channel's ability to operate correctly. The clinical consequences of such variants depend on their specific nature and location, influencing how severely the protein's activity is affected.
Sample of pathogenic variants
3 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 |
|---|---|---|---|---|
g.(?_47938438)_(47945449_?)del | - | Pathogenic | ★☆☆☆ | not provided |
g.(?_47938438)_(47954718_?)del | - | Pathogenic | ★☆☆☆ | not provided |
g.(?_47936421)_(47943412_?)del | - | 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 *CNGA1* gene are associated with various inherited retinal disorders, reflecting its critical role in visual function. These conditions typically affect the photoreceptor cells, leading to progressive vision loss. The observed inheritance patterns can vary, which impacts how these conditions are passed through families.
No disease links recorded for this gene in our reference set.
UK clinical status
The *CNGA1* gene is recognised within the NHS Genomic Medicine Service (GMS) pathways. It is currently listed on the Retinal disorders panel (R32) in PanelApp, which indicates that it is an established gene for testing in patients presenting with these conditions within the UK.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the primary function of the CNGA1 gene?
The *CNGA1* gene provides instructions for a protein subunit that forms part of a cyclic nucleotide-gated ion channel. This channel is crucial for converting light signals into electrical impulses in the eye's photoreceptor cells, enabling vision.
How do variants in the CNGA1 gene affect vision?
Variants in *CNGA1* can disrupt the normal function of the ion channel it forms. This disruption impairs the ability of photoreceptor cells to properly process light, which can lead to various inherited retinal disorders and progressive vision loss.
Is the CNGA1 gene tested in the UK?
Yes, the *CNGA1* gene is included in the NHS Genomic Medicine Service's Retinal disorders panel (R32) within PanelApp, indicating its relevance for genetic testing in the UK for individuals with suspected retinal conditions.