CFTR rs113993959: What Your Genotype Means
The rs113993959 variant, also known as p.Gly542Ter or G542X, is a specific genetic change within the CFTR gene. It is recognized as a pathogenic mutation and is included in standard reproductive carrier screening panels due to its association with cystic fibrosis.
What each genotype means
Typical CFTR genotype
This genotype represents the common, non-mutated sequence at this position in the CFTR gene. It is not associated with the specific G542X (p.Gly542Ter) cystic fibrosis mutation.
This is the most common genotype observed in the general population across all ancestries.
Cystic fibrosis carrier
This genotype indicates you carry one copy of the G542X (p.Gly542Ter) mutation in the CFTR gene. Carriers are typically asymptomatic, but you should discuss reproductive carrier screening and family planning with a genetic counselor or healthcare provider.
This variant is found at a global allele frequency of approximately 0.0007, with higher prevalence in Mediterranean and Ashkenazi Jewish lineages.
Cystic fibrosis associated
This genotype indicates you carry two copies of the G542X (p.Gly542Ter) mutation. This mutation is a well-characterized pathogenic variant associated with cystic fibrosis, and you should consult with a medical specialist for clinical evaluation and management.
This homozygous genotype is extremely rare in the general population.
Understanding the Variant
The variant rs113993959 is a single nucleotide polymorphism (SNP) located on chromosome 7 within the CFTR gene. In scientific literature, it is frequently referred to as c.1624G>T or p.Gly542Ter, indicating that a guanine is replaced by a thymine at a specific position. This change results in a premature stop codon, which instructs the cell to stop building the CFTR protein before it is complete. Because the resulting protein is truncated and typically non-functional, this variant is classified as a pathogenic mutation. It is one of the most well-studied variants in the CFTR gene and is a standard inclusion in clinical carrier screening programs recommended by organizations like the American College of Medical Genetics and Genomics (ACMG).
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 that transports negatively charged chloride ions into and out of cells. This movement of ions is essential for maintaining the proper balance of salt and water on cell surfaces, which helps produce thin, free-flowing mucus in organs such as the lungs, pancreas, and digestive tract. When the CFTR gene contains a pathogenic mutation like rs113993959, the resulting protein is either absent or unable to function correctly. This disruption leads to the production of thick, sticky mucus that can clog airways and ducts, which is the hallmark of cystic fibrosis. Understanding this gene is critical for identifying individuals who may be carriers of these mutations.
Research and Clinical Significance
Research has firmly established that rs113993959 is a pathogenic variant associated with cystic fibrosis. It is considered one of the most common CFTR mutations in certain populations, particularly those of Mediterranean descent. Because it is a severe mutation, individuals who inherit two copies of this variant (one from each parent) are at high risk for developing cystic fibrosis. Individuals who carry only one copy are typically asymptomatic carriers. While the evidence for its pathogenicity is strong, the clinical expression of cystic fibrosis can vary significantly between individuals, even those with the same genotype. This variability is influenced by other genetic factors and environmental modifiers. If you have questions about your carrier status or the implications of this variant for your health or family planning, it is essential to discuss these results with a qualified genetic counselor or your primary healthcare provider.
What You Can Do With This Information
Knowing your status for the rs113993959 variant is primarily useful for reproductive planning and understanding your risk of being a carrier for cystic fibrosis. If you are identified as a carrier, it does not mean you have the disease, but it does mean there is a possibility of passing the variant to your children. If both parents are carriers of a CFTR mutation, there is a 25% chance with each pregnancy that the child will inherit two copies of the mutation and potentially develop cystic fibrosis. This information should not be used to self-diagnose or make medical decisions without professional guidance. Always consult with a medical professional to interpret genetic test results in the context of your personal and family medical history. They can provide accurate information regarding testing for partners and the availability of reproductive options.
How common is this variant?
The global allele frequency of this variant is approximately 0.0007 in the gnomAD database, though it is notably more common in Mediterranean lineages.
Frequently asked questions
What does it mean to be a carrier for the G542X mutation?
Being a carrier means you have one copy of the mutated gene and one normal copy. Carriers typically do not show symptoms of cystic fibrosis but can pass the mutation to their children.
Is rs113993959 the same as G542X?
Yes, rs113993959 is the unique identifier (rsID) for the genetic variant commonly known as G542X or p.Gly542Ter. These names all refer to the same specific change in the CFTR gene.
Should I be worried if I have this variant?
Identifying this variant is a tool for reproductive health awareness. You should discuss the results with a genetic counselor to understand what it means for your specific situation and family planning.
Does this variant cause other health conditions?
While primarily associated with cystic fibrosis, some CFTR mutations are also linked to other conditions like hereditary pancreatitis. Consult a doctor to understand the full clinical picture.
Sources & further reading
Educational information only, last refreshed 10/14/2026. 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 frameshift mutation (c.3659delC) in CFTR linked to cystic fibrosis.
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.