What you carry at this position in your DNA and what research says about it.
Corneal Health and Fuchs Risk: 8/10 evidence, 37 publications.
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Sample genotype (not yours): G/G
High Risk of Fuchs Corneal Dystrophy
Carrying two copies of the G allele is associated with a significantly elevated risk of developing Fuchs' corneal dystrophy. This condition affects the inner layer of the cornea and can lead to blurred vision.
What this genotype means: Significantly higher risk of Fuchs' corneal dystrophy; Slightly higher cognitive performance; Slightly increased likelihood of mood instability.
Sample genotype (not yours): G/T
Elevated Risk of Fuchs Corneal Dystrophy
Carrying one copy of the G allele increases the risk of developing Fuchs' corneal dystrophy.
What this genotype means: Moderately higher risk of Fuchs' corneal dystrophy; Slightly higher cognitive performance; Slightly increased likelihood of mood instability.
Sample genotype (not yours): T/T
Typical Risk of Fuchs Corneal Dystrophy
Carrying two copies of the T allele is associated with a typical, baseline risk of Fuchs' corneal dystrophy. This is the most common genotype globally.
What this genotype means: Typical baseline risk of Fuchs' corneal dystrophy; Typical baseline cognitive performance; Slightly higher likelihood of tinnitus.
Gene function and biological role
Gene Function: Transcription factor 4, encoded by the TCF4 gene, is a crucial protein that regulates the expression of numerous other genes during development [1]. It belongs to the basic helix-loop-helix family of transcription factors and is widely expressed in the brain and corneal endothelial cells [1]. Proper functioning of this protein is essential for maintaining the health and hydration of the cornea [2]. Variations in this gene can disrupt normal cellular development and have been linked to both neurological traits and corneal disorders [1] [2].
Variant Impact: The rs613872 variant is located within an intron, or non-coding region, of the TCF4 gene. Although it does not directly alter the amino acid sequence of the protein, it serves as a powerful genetic marker for nearby trinucleotide repeat expansions [3]. These expansions can significantly alter the splicing and expression levels of the TCF4 gene in corneal tissues [3]. Consequently, this specific genetic change is heavily studied for its profound impact on corneal cell survival and overall eye health [2].
Key Insight: The G allele of this variant is one of the strongest genetic risk factors known for Fuchs' corneal dystrophy, yet many carriers never develop the condition, pointing to other environmental or genetic modifiers.
Location: TCF4. Chromosome 18 · 18q21.2 · 55.5 Mb
Estimated prevalence by population
Global 1.8%; European 2.8%; African 0.1%; East Asian < 0.1%; South Asian 1.6%; Americas 0.9%; Ashkenazi 5.9%; Finnish 2.3%; Middle Eastern 1.8%; Amish 12.3%.
Estimated GG genotype frequency.
Global 19.7%; European 27.8%; African 5.8%; East Asian 0.4%; South Asian 22.0%; Americas 17.2%; Ashkenazi 36.8%; Finnish 25.8%; Middle Eastern 23.0%; Amish 45.6%.
Estimated GT genotype frequency.
Global 78.5%; European 69.4%; African 94.1%; East Asian 99.6%; South Asian 76.4%; Americas 81.9%; Ashkenazi 57.3%; Finnish 71.9%; Middle Eastern 75.2%; Amish 42.1%.
Estimated TT genotype frequency.
Showing effects for G/G genotype
Organ Systems
Vision & Eye Health
Fuchs Corneal Dystrophy. Evidence: 4/10. Source: PMID 20825314. ~20-30x Higher Risk.
Hearing & Balance
Tinnitus. Evidence: 6/10. Source: PMID 38242899. Typical Risk.
Neurology & Mental Health
Cognitive Performance
Cognitive Function. Evidence: 6/10. Source: PMID 30038396. Slightly Higher.
Educational Attainment. Evidence: 8/10. Source: PMID 30038396. Slightly Higher.
Mood Disorders
Mood Instability. Evidence: 7/10. Source: PMID 31168069. Slightly Higher.
Showing effects for G/T genotype
Fuchs Corneal Dystrophy. Evidence: 4/10. Source: PMID 20825314. ~5x Higher Risk.
Tinnitus. Evidence: 6/10. Source: PMID 38242899. Slightly Higher.
Showing effects for T/T genotype
Fuchs Corneal Dystrophy. Evidence: 4/10. Source: PMID 20825314. Typical Risk.
Cognitive Function. Evidence: 6/10. Source: PMID 30038396. Typical.
Educational Attainment. Evidence: 8/10. Source: PMID 30038396. Typical.
Mood Instability. Evidence: 7/10. Source: PMID 31168069. Typical.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Corneal endothelial cells rely on precise transcription factor activity to maintain the fluid balance required for clear vision. A 20- to 30-fold increase in the risk of developing Fuchs' endothelial corneal dystrophy is strongly linked to this genetic profile [1]. This progressive condition causes gradual loss of corneal endothelial cells, leading to swelling, discomfort, and eventual vision impairment [1]. Interestingly, this same genetic profile is also associated with slightly higher cognitive function and educational attainment [2]. However, the potential for corneal issues remains the most clinically significant aspect of this genotype.
Significantly higher risk of Fuchs' corneal dystrophy; Slightly higher cognitive performance; Slightly increased likelihood of mood instability.
Sample genotype: GT (Heterozygous)
Endothelial cells in the cornea require stable TCF4 expression to pump out excess fluid and maintain transparency. An approximately 5-fold increase in the risk of Fuchs' corneal dystrophy is associated with this genetic profile [1]. While this risk is lower than that of individuals with two G alleles, it still represents a notable elevation compared to the general population [1]. On the positive side, this genotype is also linked to a slight increase in cognitive performance and educational attainment [2]. Some individuals with this genetic makeup may also experience a slightly higher tendency toward mood instability [3].
Moderately higher risk of Fuchs' corneal dystrophy; Slightly higher cognitive performance; Slightly increased likelihood of mood instability.
Sample genotype: TT (Homozygous)
Corneal health is typically well-maintained in individuals carrying two copies of the T allele, as they lack the risk-associated G variant. The risk of developing Fuchs' endothelial corneal dystrophy remains at the baseline population level, which is generally low [1]. This genotype represents the standard genetic background for the majority of people worldwide. While corneal health is favored, this profile is associated with typical baseline levels of cognitive function and educational attainment rather than the slight elevations seen with the G allele [2]. Additionally, there is a slightly higher statistical likelihood of experiencing tinnitus compared to G-allele carriers [3].
Typical baseline risk of Fuchs' corneal dystrophy; Typical baseline cognitive performance; Slightly higher likelihood of tinnitus.
Variants with shared genetic architecture
rs9960767 · TCF4 Gene · Chr 18 · Schizophrenia Risk
rs2745572 · FOXC1 Gene · Chr 6 · Glaucoma Risk
rs33912345 · SIX6 Gene · Chr 14 · Glaucoma Risk
E2-2 protein and Fuchs's corneal dystrophy.
Genetic architecture distinguishes tinnitus from hearing loss.
Content updated August 2026.
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