CFTR rs121908811: Understanding the c.3659delC Variant
The rs121908811 variant is a specific genetic change in the CFTR gene known as c.3659delC. It is recognized in clinical literature as a pathogenic variant associated with cystic fibrosis.
What each genotype means
Typical risk profile
You do not carry the c.3659delC deletion at this site in the CFTR gene. This common genotype does not indicate increased carrier risk for cystic fibrosis related to this specific variant. Because cystic fibrosis can result from hundreds of different CFTR variants, this result alone does not rule out carrier status for other mutations.
Carried by more than 99.9% of individuals across global populations.
Cystic fibrosis carrier
You carry one copy of the c.3659delC (p.Thr1220Lysfs) frameshift variant in the CFTR gene, classifying you as an unaffected carrier of autosomal recessive cystic fibrosis. Carriers generally do not display classic cystic fibrosis symptoms, but have a 50% chance of passing this variant to their biological children. Genetic counseling and reproductive carrier testing for partners are commonly recommended to assess family planning considerations.
Very rare globally with an overall frequency under 0.01%, though enriched in specific pan-ethnic clinical screening panels.
What is the rs121908811 Variant?
The rs121908811 variant is a deletion of a single cytosine nucleotide within the CFTR gene, specifically identified as c.3659delC. In genetic terms, this is classified as a frameshift mutation. Because the genetic code is read in groups of three nucleotides, the removal of one base shifts the entire reading frame of the gene sequence. This shift typically results in the production of an altered protein sequence, often leading to a premature stop codon. In the case of this specific variant, the change occurs at codon 1220, resulting in a protein product that is truncated and likely non-functional. This variant is located on chromosome 7 and is documented in major genomic databases as a significant alteration within the CFTR sequence.
The Role of the CFTR Gene
The CFTR gene provides instructions for making the cystic fibrosis transmembrane conductance regulator protein. This protein functions as a channel across the membranes of cells that produce mucus, sweat, saliva, tears, and digestive enzymes. By transporting negatively charged particles called chloride ions into and out of cells, the CFTR protein helps control the movement of water in tissues, which is necessary for the production of thin, freely flowing mucus. When the CFTR gene is mutated, the resulting protein may be missing, non-functional, or present in insufficient quantities. This leads to the production of thick, sticky mucus that can clog airways and ducts in the lungs, pancreas, and other organs, which is the hallmark of cystic fibrosis.
Research and Clinical Associations
Research has established a link between the rs121908811 variant and cystic fibrosis. Because it is a frameshift mutation that disrupts the normal production of the CFTR protein, it is categorized as pathogenic in clinical databases like ClinVar. While the primary association is with cystic fibrosis, it is important to note that the severity of the condition can vary based on the presence of other mutations in the CFTR gene. The evidence for this variant's pathogenicity is supported by its identification in individuals diagnosed with the condition. However, because cystic fibrosis is a complex, recessive condition, the presence of this variant alone does not provide a complete clinical picture. Genetic testing results should always be interpreted by a qualified healthcare professional who can consider the full genetic context and clinical history.
Population Frequency
The rs121908811 variant is considered rare in the general population. According to available genomic data, the minor allele frequency is reported to be less than 0.0001. This low frequency is consistent with many pathogenic variants associated with severe recessive conditions, which are typically maintained at low levels in the gene pool. Because it is so uncommon, it is not frequently encountered in standard population screening unless specifically targeted by a diagnostic panel. The rarity of this variant underscores the importance of specialized genetic testing for individuals with a family history of cystic fibrosis or those seeking carrier screening.
Interpreting Your Genetic Information
If you have received information regarding the rs121908811 variant, it is essential to understand what this means in a practical sense. This information is for educational purposes and does not constitute a medical diagnosis. Genetic variants are only one piece of a larger health puzzle. If you are concerned about your carrier status or the potential for passing a genetic condition to children, you should consult with a genetic counselor or a medical geneticist. These professionals can help you understand the implications of your specific genotype, discuss the necessity of further diagnostic testing, and provide guidance based on your personal and family health history. Never make medical decisions based solely on raw genetic data without professional clinical consultation.
How common is this variant?
The rs121908811 variant is very rare, with a minor allele frequency of less than 0.0001 across global populations.
Frequently asked questions
What does it mean to be a carrier of a CFTR mutation?
Being a carrier means you have one copy of a mutated CFTR gene and one normal copy. Carriers typically do not show symptoms of cystic fibrosis but can pass the mutation to their children.
Is rs121908811 the same as the common Delta F508 mutation?
No, rs121908811 is a different, less common mutation than the Delta F508 variant. While both occur in the CFTR gene, they are distinct genetic changes.
Can I use this information to diagnose myself?
No, genetic data from testing services is not a medical diagnosis. You must discuss any findings with a healthcare provider who can interpret the results in the context of your health.
Where can I find more information about CFTR mutations?
You can visit resources like MedlinePlus Genetics or the ClinVar database for authoritative information on CFTR and its associated variants. Always prioritize information from established medical and scientific institutions.
Sources & further reading
Educational information only, last refreshed 10/11/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Severe pathogenic mutation (p.Gly542Ter) associated with cystic fibrosis.
Classic cystic fibrosis in-frame 3-bp deletion variant (p.Phe508del / deltaF508) causing misfolding and impaired chloride channel trafficking.
Pathogenic nonsense variant (p.Gly542Ter / G542X) causing autosomal recessive cystic fibrosis when inherited in trans with another CFTR pathogenic allele.
Also known as p.Arg117His (R117H), this CFTR variant is associated with mild or atypical cystic fibrosis and congenital bilateral absence of the vas deferens, with clinical severity influenced by the poly-T tract background.
A CFTR mutation associated with cystic fibrosis and CFTR-related disorders.
A pathogenic variant (p.Arg117His) in the CFTR gene associated with CFTR-related disorders.