CFTR rs121908812: Understanding This Genetic Variant
The rs121908812 variant is a specific change within the CFTR gene that is recognized as a pathogenic mutation. It is primarily associated with cystic fibrosis carrier status, meaning individuals who carry this variant may be at risk of passing it to their offspring.
What each genotype means
Typical CFTR gene profile
This genotype represents the common, non-mutated sequence at this specific location in the CFTR gene. It is considered the reference sequence and is not associated with the pathogenic deletion described for this variant.
This is the most common genotype found in the general population.
Cystic fibrosis carrier status
This genotype indicates the presence of a pathogenic deletion (c.2012delT) in one copy of the CFTR gene. Individuals with this result are considered carriers of a cystic fibrosis-associated mutation, which means they do not typically exhibit symptoms of the condition themselves but may pass the variant to their children.
This genotype is rare in the general population.
What is the rs121908812 Variant?
The rs121908812 variant is a single nucleotide change located within the CFTR gene on chromosome 7. In genetic databases, it is often identified by its specific molecular impact, such as a deletion of a thymine base, which alters the genetic code at that position. Because the CFTR gene provides instructions for making a protein that acts as a channel for chloride ions, changes to this sequence can disrupt the protein's normal function. This specific variant is classified as pathogenic, meaning it is known to cause or contribute to disease when present in certain combinations. It is tracked by researchers and clinicians through international databases like ClinVar to help identify individuals who may be carriers of cystic fibrosis-related mutations.
The Role of the CFTR Gene
The CFTR gene encodes the Cystic Fibrosis Transmembrane conductance Regulator protein. This protein is essential for the movement of chloride ions and water across the membranes of cells that line various organs, including the lungs, pancreas, and digestive tract. When the CFTR protein is absent or malfunctioning, these cells cannot properly regulate the flow of fluids, leading to the production of abnormally thick and sticky mucus. This mucus can obstruct airways and ducts, which is the hallmark of cystic fibrosis. Because the gene is inherited in an autosomal recessive pattern, an individual typically needs to inherit two copies of a pathogenic variant—one from each parent—to manifest the clinical symptoms of the condition.
Research and Clinical Evidence
Scientific research has firmly established that pathogenic variants in the CFTR gene are the cause of cystic fibrosis. The evidence for rs121908812 is considered moderate to strong in the context of clinical genetics, as it is documented in databases like the CFTR2 (Clinical and Functional Translation of CFTR) project. Studies have shown that this variant disrupts the production or stability of the CFTR protein. While the presence of this variant is a significant finding, it is important to note that the severity of cystic fibrosis can vary widely depending on the specific combination of variants an individual carries. Researchers continue to study how different mutations interact to influence the clinical presentation of the disease.
Population Frequency
The rs121908812 variant is considered rare in the general population. Because it is a pathogenic mutation associated with a specific recessive condition, it does not appear at high frequencies in large-scale genomic databases like gnomAD. Its distribution is often linked to specific ancestral backgrounds where certain CFTR mutations have historically been more prevalent. Genetic screening programs often look for this variant alongside hundreds of others to provide comprehensive carrier testing. Due to its rarity, most individuals will not carry this specific change, but those who do are often identified through targeted clinical testing rather than population-wide screening.
What This Information Means for You
If you have been informed that you carry the rs121908812 variant, it is important to understand that this is a carrier status finding. Being a carrier generally means you have one copy of a pathogenic variant and one functional copy of the gene, which typically does not result in the symptoms of cystic fibrosis. However, if your partner is also a carrier of a CFTR mutation, there is a statistical possibility of passing the condition to your children. This information is not a medical diagnosis and should not be used to make health decisions on your own. You should discuss these results with a genetic counselor or a qualified healthcare provider who can explain the implications for your family planning and overall health.
How common is this variant?
The rs121908812 variant is rare across all major global populations, appearing only sporadically in clinical and research databases.
Frequently asked questions
What does it mean to be a carrier for cystic fibrosis?
Being a carrier means you have one copy of a gene mutation that causes cystic fibrosis, but you do not have the disease yourself. You have one normal copy of the gene that allows your body to function correctly.
Can I get cystic fibrosis if I only have one copy of this variant?
No, cystic fibrosis is an autosomal recessive condition, which means it typically requires two copies of a pathogenic mutation to manifest symptoms. Having only one copy makes you a carrier, not a person with the disease.
Should I be worried if I have this variant?
Finding out you are a carrier is useful information for family planning, but it does not mean you are ill. You should consult with a genetic counselor to understand the risks and what this means for your future children.
Is this variant the same as the common DeltaF508 mutation?
No, rs121908812 is a distinct variant from the DeltaF508 mutation. While both are located in the CFTR gene and are associated with cystic fibrosis, they are different genetic changes.
Sources & further reading
Educational information only, last refreshed 9/27/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Pathogenic CFTR splice-site mutation (c.1585-1G>A / 1717-1G>A) causing cystic fibrosis when inherited in trans with another pathogenic allele.
Well-characterized pathogenic CFTR nonsense mutation (p.Gly542Ter) included in standard ACMG/ACOG reproductive carrier screening recommendations.
Pathogenic CFTR missense variant (p.Arg334Trp) associated with classic or atypical cystic fibrosis in expanded carrier screening panels.
Pathogenic CFTR missense variant (p.Arg347His) causing defective chloride conductance, tested in expanded reproductive carrier screening for cystic fibrosis.
This variant is identified as a carrier allele for cystic fibrosis.
This variant is a known pathogenic allele associated with cystic fibrosis carrier status.