What you carry at this position in your DNA and what research says about it.
Heart and Brain Health: 8/10 evidence, 30 publications.
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Sample genotype (not yours): G/G
Higher Risk of Atrial Fibrillation
This genotype is associated with an increased risk of developing atrial fibrillation and other cardiac arrhythmias. However, it is linked to a lower risk of progressive supranuclear palsy and lower circulating tau levels.
What this genotype means: Increased risk of atrial fibrillation; Increased risk of cardiac arrhythmia; Lower risk of progressive supranuclear palsy.
Sample genotype (not yours): A/A
Higher Risk of Progressive Supranuclear Palsy
This genotype is linked to an increased risk of progressive supranuclear palsy and higher circulating tau levels. However, it is associated with a lower risk of atrial fibrillation.
What this genotype means: Increased risk of progressive supranuclear palsy; Higher circulating tau levels; Increased risk of dilated cardiomyopathy.
Sample genotype (not yours): G/A
Typical Risk of Heart and Neurological Conditions
This genotype represents a balanced genetic profile with typical risk levels for both cardiovascular and neurodegenerative conditions. It is the most common genotype globally.
What this genotype means: Typical risk of atrial fibrillation; Typical risk of progressive supranuclear palsy; Typical levels of circulating tau protein.
Gene function and biological role
Gene Function: The MAPT gene provides instructions for making a protein called tau, which is abundant in neurons of the central nervous system [1]. Tau protein plays a critical role in stabilizing microtubules, which act as cellular tracks for transporting nutrients and other materials within nerve cells [1]. When tau protein becomes abnormal or hyperphosphorylated, it can clump together to form toxic tangles that disrupt cell function and lead to cell death [2]. These tau aggregates are a hallmark of several neurodegenerative diseases collectively known as tauopathies, including Alzheimer's disease and progressive supranuclear palsy [2] [3].
Variant Impact: The rs242557 variant is located in an intronic region of the MAPT gene and acts as a key genetic marker for the H1c subhaplotype [2]. This specific genetic variation is known to influence the expression levels of the tau protein in the brain and body [2] [4]. The A allele of this variant is associated with higher levels of circulating total tau in both plasma and cerebrospinal fluid [4] [5]. Conversely, the G allele has been linked to altered cardiac electrical activity, increasing the susceptibility to certain heart rhythm disorders [6].
Key Insight: The same genetic variant that increases the risk of certain heart rhythm disorders actually lowers the risk of rare neurodegenerative brain diseases.
Location: MAPT. Chromosome 17 · 17q21.31 · 45.9 Mb
Estimated prevalence by population
Global 40.8%; European 39.7%; African 47.0%; East Asian 19.6%; South Asian 34.8%; Americas 43.9%; Ashkenazi 50.0%; Finnish 28.5%; Middle Eastern 46.3%; Amish 30.3%.
Estimated GG genotype frequency.
Global 45.7%; European 46.6%; African 43.1%; East Asian 49.3%; South Asian 48.4%; Americas 44.7%; Ashkenazi 41.4%; Finnish 49.8%; Middle Eastern 43.5%; Amish 49.5%.
Estimated GA genotype frequency.
Global 13.5%; European 13.7%; African 9.9%; East Asian 31.1%; South Asian 16.9%; Americas 11.4%; Ashkenazi 8.6%; Finnish 21.7%; Middle Eastern 10.2%; Amish 20.2%.
Estimated AA genotype frequency.
Showing effects for G/G genotype
Cardiovascular & Metabolic
Heart Rhythm & Conduction
Atrial Fibrillation. Evidence: 8/10. Source: PMID 29892015. Increased Risk.
Cardiac Arrhythmia. Evidence: 6/10. Source: PMID 32514122. Increased Risk.
Heart Disease
Dilated Cardiomyopathy. Evidence: 4/10. Source: PMID 39572784. Typical Risk.
Neurology & Mental Health
Neurodegenerative Diseases
Progressive Supranuclear Palsy. Evidence: 6/10. Source: PMID 21685912. Typical Risk.
Total Tau Levels. Evidence: 8/10. Source: PMID 28100725. Lower Levels.
Showing effects for A/A genotype
Atrial Fibrillation. Evidence: 8/10. Source: PMID 29892015. Typical Risk.
Cardiac Arrhythmia. Evidence: 6/10. Source: PMID 32514122. Typical Risk.
Dilated Cardiomyopathy. Evidence: 4/10. Source: PMID 39572784. Increased Risk.
Progressive Supranuclear Palsy. Evidence: 6/10. Source: PMID 21685912. Increased Risk.
Total Tau Levels. Evidence: 8/10. Source: PMID 28100725. Higher Levels.
Showing effects for G/A genotype
Atrial Fibrillation. Evidence: 8/10. Source: PMID 29892015. Slightly Increased.
Cardiac Arrhythmia. Evidence: 6/10. Source: PMID 32514122. Slightly Increased.
Dilated Cardiomyopathy. Evidence: 4/10. Source: PMID 39572784. Slightly Increased.
Progressive Supranuclear Palsy. Evidence: 6/10. Source: PMID 21685912. Slightly Increased.
Total Tau Levels. Evidence: 8/10. Source: PMID 28100725. Typical Levels.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Carrying two copies of the G allele is associated with a higher susceptibility to atrial fibrillation, a common heart rhythm disorder [1]. Large-scale genetic studies have demonstrated a consistent link between this genotype and elevated odds of cardiac arrhythmias [1] [2]. On the neurological side, this genotype appears to be protective against certain rare neurodegenerative conditions [3]. It is associated with lower levels of total tau protein in the blood and cerebrospinal fluid, which may reduce the formation of toxic tau tangles in brain tissue [4]. While the risk of progressive supranuclear palsy is significantly lower for individuals with this genotype, maintaining cardiovascular health remains a key focus [3].
Increased risk of atrial fibrillation; Increased risk of cardiac arrhythmia; Lower risk of progressive supranuclear palsy.
Sample genotype: AA (Homozygous)
Carrying two copies of the A allele is a well-established risk factor for progressive supranuclear palsy, a rare but severe neurodegenerative disorder [1]. This genetic variation is thought to increase the expression of tau protein, leading to higher levels of total tau in the plasma and brain [2] [3]. Elevated tau levels can promote the accumulation of toxic protein aggregates that damage nerve cells over time [4]. Additionally, this genotype is associated with an increased risk of dilated cardiomyopathy, a condition affecting the heart muscle [5]. On the positive side, individuals with this genotype have a lower risk of developing atrial fibrillation and other common cardiac arrhythmias [6].
Increased risk of progressive supranuclear palsy; Higher circulating tau levels; Increased risk of dilated cardiomyopathy; Lower risk of atrial fibrillation.
Sample genotype: GA (Heterozygous)
Having one copy of each allele generally results in intermediate levels of tau protein expression and typical cardiovascular risk [1]. This heterozygous profile is considered the baseline or normal state in most genetic analyses [2]. Studies show that the risk for developing atrial fibrillation or cardiac arrhythmias is not as elevated as in those with the G/G genotype [3]. Similarly, the risk for progressive supranuclear palsy and other tau-related neurodegenerative disorders is lower than in those with the A/A genotype [4]. Because this genotype is highly common, it serves as a standard reference point for health outcomes.
Typical risk of atrial fibrillation; Typical risk of progressive supranuclear palsy; Typical levels of circulating tau protein.
Variants with shared genetic architecture
rs2471738 · MAPT Gene · Chr 17 · Alzheimer's and Cognition
rs3785883 · MAPT Gene · Chr 17 · Cognitive Decline Risk
rs8070723 · MAPT Gene · Chr 17 · Progressive Supranuclear Palsy
Identification of common variants influencing risk of the tauopathy progressive supranuclear palsy.
The associations between the MAPT polymorphisms and Alzheimer's disease risk: a meta-analysis.
Genome-wide association study identifies MAPT locus influencing human plasma tau levels.
Multi-ethnic genome-wide association study for atrial fibrillation.
Structural study of the microtubule-associated protein tau locus of Alzheimer's disease in Taiwan.
Content updated August 2026.
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