GP1BA rs6065: The HPA-2 Platelet Antigen Explained
The genetic variant rs6065 is a missense single nucleotide polymorphism situated in the GP1BA gene on chromosome 17. It defines the human platelet alloantigen-2 (HPA-2) system by swapping a threonine for a methionine at position 161 of the glycoprotein Ib-alpha chain. This variant has been investigated for its subtle influence on platelet adhesion and statistical associations with arterial thrombosis and coronary artery disease, though clinical evidence remains limited.
What each genotype means
Typical platelet antigen profile
You carry two copies of the C allele, which corresponds to the common HPA-2a (Thr161) form of the platelet glycoprotein Ib alpha subunit. Research indicates typical platelet receptor functioning without the modest differences in arterial thrombosis risk associated with the alternative allele. However, scientific evidence linking this locus to cardiovascular outcomes remains limited and mixed across diverse populations.
Carried by approximately 80% of individuals of European ancestry and roughly 90% of individuals of East Asian ancestry.
Heterozygous HPA-2 antigen profile
You carry one copy of the C allele and one copy of the T allele (encoding the HPA-2b or Met161 variant). Some observational studies have reported a slightly higher susceptibility to coronary artery disease or ischemic stroke among carriers of this allele, whereas other studies find no significant association. If you are taking antiplatelet medications such as aspirin, any potential effects on drug response remain under preliminary research and should be discussed with your clinician.
Carried by roughly 15% to 20% of people of European descent and about 8% to 10% of individuals of East Asian descent.
Homozygous HPA-2b antigen profile
You carry two copies of the T allele, encoding the less common HPA-2b (Met161) platelet membrane antigen. Certain epidemiological analyses suggest a possible correlation with altered platelet signaling and arterial thrombotic events, though overall findings across ancestral groups remain inconsistent. If you have questions about cardiovascular wellness or antiplatelet therapy, consult your healthcare provider.
Carried by approximately 1% of individuals of European ancestry and fewer than 1 in 300 individuals of East Asian ancestry.
Genomic Context and the HPA-2 Variant
The single nucleotide polymorphism rs6065 is located on chromosome 17 within the coding region of the GP1BA gene, as documented in NCBI's [dbSNP](https://www.ncbi.nlm.nih.gov/snp/rs6065). At the molecular level, this transition variant involves an exchange between cytosine (C) and thymine (T) alleles. In the primary translated protein sequence, this nucleotide change leads to a missense substitution of threonine with methionine (frequently designated as Met161Thr or Thr145Met depending on the signal peptide numbering). Historically, this polymorphism forms the immunological basis for the human platelet alloantigen 2 (HPA-2) system, where the C allele represents the HPA-2a alloantigen and the alternative T allele corresponds to HPA-2b. While rare loss-of-function disruptions in GP1BA cause monogenic bleeding disorders such as Bernard-Soulier syndrome, rs6065 is a common evolutionary polymorphism that exerts far milder, nuanced modulations on platelet physiology.
Biological Role of the GP1BA Receptor
The GP1BA gene provides instructions for producing the alpha subunit of platelet glycoprotein Ib (GPIb-alpha). This protein is a central component of the membrane-bound GPIb-IX-V receptor complex, which plays an essential role in early hemostasis. When a blood vessel wall is injured, endothelial damage exposes collagen and circulating von Willebrand factor (VWF). The GPIb-alpha chain directly binds to the A1 domain of VWF, allowing circulating blood platelets to roll, adhere, and tether onto the damaged vessel wall under high-shear vascular flow. Because position 161 resides in the functional extracellular region of the receptor, the Met161Thr substitution has been hypothesized to subtly shift receptor conformation and downstream signal transduction during platelet activation and aggregation.
Research Findings and Cardiovascular Risk
Epidemiological studies and candidate-gene investigations have evaluated rs6065 for potential associations with ischemic stroke, myocardial infarction, and coronary artery disease, as reviewed in cardiovascular literature on [PubMed](https://pubmed.ncbi.nlm.nih.gov/?term=rs6065). Some observational cohorts reported modest correlations between the minor T allele (HPA-2b) and altered susceptibility to arterial thrombotic events or small variations in baseline platelet counts. However, larger meta-analyses and systematic reviews in broad populations frequently report mixed, inconsistent, or null associations. Furthermore, entries in databases like ClinVar annotate rs6065 under drug-response categories regarding antiplatelet therapy such as aspirin, but without definitive outcome links. Consequently, the overall clinical evidence connecting rs6065 to coronary heart disease and thrombosis is officially classified as limited and non-definitive.
Interpreting Genetic Results in Daily Life
Understanding your rs6065 genotype provides interesting educational context regarding platelet biology, but it is not a standalone clinical diagnostic marker. Having one or two copies of the T allele does not indicate that you will develop a blood clot, heart disease, or a bleeding complication. Cardiovascular health is complex, polygenic, and strongly influenced by established lifestyle and metabolic factors such as blood pressure, lipid profiles, diet, exercise, and smoking history. Genetic findings for rs6065 cannot replace comprehensive cardiovascular risk assessments. Furthermore, anyone taking antiplatelet medications such as aspirin or clopidogrel should never adjust or discontinue their prescribed therapy based on home genetic tests; any medication-response questions must always be reviewed directly with a physician or clinical pharmacist.
How common is this variant?
The minor T allele occurs at a frequency of approximately 0.10 in populations of European ancestry and roughly 0.05 in East Asian populations, making the CC genotype the predominant form globally.
Frequently asked questions
What is the HPA-2 platelet antigen system?
The human platelet alloantigen-2 (HPA-2) system is an immunological typing system based on structural variations in the GPIb-alpha platelet receptor. The rs6065 single nucleotide polymorphism determines whether an individual expresses the HPA-2a form (threonine) or the HPA-2b form (methionine), which can sometimes play a role in alloimmune platelet reactions.
Does having the rs6065 TT genotype mean I will get a blood clot?
No. While some historical studies explored whether the T allele slightly alters platelet aggregation or arterial clot risk, modern evidence is limited and conflicting. Possessing this genotype is not an independent diagnostic indicator of thrombosis.
Is rs6065 related to Bernard-Soulier syndrome?
No. While rare, deleterious loss-of-function mutations throughout the GP1BA gene cause the severe inherited bleeding disorder Bernard-Soulier syndrome, rs6065 is a benign, common polymorphism that does not cause this syndrome.
Should I adjust my aspirin or antiplatelet medication based on this variant?
No. Although rs6065 has been investigated for subtle influences on platelet response, current clinical guidelines do not support altering antiplatelet therapy based on this variant. Always consult your prescribing physician or pharmacist before changing any medication.
Sources & further reading
Educational information only, last refreshed 9/11/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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