CNGB3 rs61748239: Understanding the p.Arg403Gln Variant
The rs61748239 variant in the CNGB3 gene is a missense mutation (p.Arg403Gln) associated with achromatopsia, a condition affecting color vision and light sensitivity. This variant impacts the function of cyclic nucleotide-gated channels in the retina's cone photoreceptor cells.
What each genotype means
Typical CNGB3 function
This genotype represents the most common genetic sequence at this location in the CNGB3 gene. Individuals with this profile do not carry the specific Arg403Gln pathogenic variant associated with complete achromatopsia.
This is the most common genotype found in the general population across all ancestries.
Carrier of variant
You carry one copy of the Arg403Gln variant in the CNGB3 gene. Because achromatopsia is an autosomal recessive condition, carrying a single copy typically does not result in the disorder, though you may pass this variant to your biological children.
This genotype is rare, occurring in less than 0.04% of the global population based on gnomAD data.
Increased risk of achromatopsia
You carry two copies of the Arg403Gln variant, which is a known cause of complete achromatopsia. This condition affects cone photoreceptor function, leading to symptoms such as impaired color vision, high sensitivity to light, and reduced visual acuity. Please consult with a clinical geneticist or ophthalmologist to discuss these findings and their implications for your vision health.
This genotype is extremely rare in the general population, as it is associated with a specific congenital disorder.
What is rs61748239?
The variant rs61748239, often referred to as p.Arg403Gln or c.1208G>A, is a specific change in the DNA sequence of the CNGB3 gene. Located on chromosome 8, this variant involves a single nucleotide substitution where guanine is replaced by adenine. This change results in an amino acid alteration in the protein product, specifically replacing arginine with glutamine at position 403. This protein, the beta-3 subunit of the cyclic nucleotide-gated (CNG) channel, is essential for the proper functioning of cone photoreceptors in the human eye. Because this variant is located within a gene critical for vision, researchers study it to understand how structural changes in ion channels can lead to inherited retinal disorders.
The Role of the CNGB3 Gene
The CNGB3 gene provides instructions for making the beta-3 subunit of a specialized ion channel found in cone photoreceptor cells. These cells are located in the retina and are responsible for color vision and vision in bright light. The CNG channels act like gates that open and close in response to chemical signals, allowing ions to flow into the cell, which is a necessary step in converting light into electrical signals sent to the brain. When the CNGB3 gene contains pathogenic variants, the resulting channels may be non-functional or absent. This disruption prevents cone cells from responding correctly to light, leading to the symptoms associated with achromatopsia, such as reduced visual acuity, extreme light sensitivity, and a limited or total inability to perceive color.
Research and Clinical Associations
Research has linked the rs61748239 variant to achromatopsia, a condition characterized by the loss of cone photoreceptor function. While many variants in CNGB3 are associated with this condition, the p.Arg403Gln variant is specifically noted for its potential to cause a variable phenotype. Some individuals carrying this variant may experience complete achromatopsia, while others might show incomplete achromatopsia or progressive cone dystrophy. Studies suggest that the severity of the condition can be influenced by other genetic factors, such as the co-occurrence of variants in the CNGA3 gene. Because the evidence for the specific clinical impact of this variant can be complex and variable, it is classified as a pathogenic variant in the context of recessive inheritance, meaning an individual typically needs to inherit the variant from both parents to manifest the condition.
Understanding Your Results
If you have received information about your status for rs61748239, it is important to understand that this is a genetic finding and not a medical diagnosis. Achromatopsia is a complex condition, and the presence of a single variant does not necessarily predict a specific clinical outcome. Genetic testing results should always be interpreted by a qualified healthcare professional or a genetic counselor who can place the findings in the context of your personal and family medical history. You cannot use this information to self-diagnose or treat any condition. If you have concerns about your vision or the health of your eyes, please consult an ophthalmologist or a clinical geneticist. They can provide appropriate clinical evaluations and discuss the implications of your genetic profile.
How common is this variant?
The rs61748239 variant is rare, with a global minor allele frequency reported in gnomAD as less than 0.0002.
Frequently asked questions
What is achromatopsia?
Achromatopsia is an inherited retinal disorder that affects cone photoreceptor cells. It results in symptoms such as significantly reduced visual acuity, extreme sensitivity to light, and a partial or total inability to see colors.
Is rs61748239 the only cause of achromatopsia?
No, achromatopsia can be caused by variants in several different genes, including CNGA3, GNAT2, and others. CNGB3 variants are responsible for approximately 50% of all cases of autosomal recessive achromatopsia.
Can I be a carrier of this variant?
Yes, if you have one copy of the variant (G/A), you are considered a carrier. Carriers typically do not show symptoms of the condition because the disorder is inherited in an autosomal recessive pattern.
Should I get tested for this variant?
Genetic testing is usually recommended by a doctor if there is a family history of retinal disorders or if you are experiencing symptoms of vision loss. You should discuss the necessity and implications of testing with a genetic counselor.
Sources & further reading
Educational information only, last refreshed 9/18/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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