rs2301612 — ADAMTS13 Q448E

Common ADAMTS13 missense variant substituting glutamate for glutamine at position 448; the G allele acts as a context-dependent modifier of ADAMTS13 enzyme function and is associated with higher rates of atrial fibrillation and cerebral ischemic events in coronary syndrome patients

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ADAMTS13 Q448E — A Coding Variant in the VWF-Cleaving Enzyme

ADAMTS1311 ADAMTS13
ADAM metallopeptidase with thrombospondin type 1 motif 13, the principal protease responsible for cleaving ultra-large von Willebrand factor (VWF) multimers in the circulation, encoded on chromosome 9q34.2 sits at the center of the VWF-platelet axis — a biological dial that determines whether platelet-rich microvascular thrombi form inappropriately. When ADAMTS13 activity is sufficient, it trims the hyper-adhesive VWF multimers released during vascular injury to safe sizes. When activity falls — through genetic variation, antibody-mediated inhibition, or acute-phase consumption — large multimers accumulate and recruit platelets into dangerous spontaneous aggregates. rs2301612 is a common missense variant in ADAMTS13 that substitutes glutamate for glutamine at position 448 (p.Gln448Glu, Q448E), placing a charged residue in a domain critical for enzyme conformation and activity.

The Mechanism

The Q448E substitution sits in the ADAMTS13 spacer domain — a region involved in substrate recognition, specifically in binding and positioning VWF for cleavage. Plaimauer et al. 200622 Plaimauer et al. 2006
Modulation of ADAMTS13 secretion and specific activity by a combination of common amino acid polymorphisms and a missense mutation. Blood. 2006;107(1):118-125. characterized Q448E using transfection experiments and found that Q448E alone has minor independent effects on ADAMTS13 secretion. However, its functional impact is highly context-dependent: in the presence of other common polymorphisms (P618A, A732V), Q448E acted as a positive modifier, partially rescuing secretion deficits — yet when co-occurring with the rare pathogenic mutation R1336W, Q448E enhanced the detrimental effect, driving ADAMTS13 activity to undetectable levels. This context-dependence means Q448E is not simply benign: its impact varies with the genetic background it inhabits.

In the largest GWAS of plasma ADAMTS13 levels, Ma et al. 201733 Ma et al. 2017
Genetic variants in ADAMTS13 as well as smoking are major determinants of plasma ADAMTS13 levels. Blood Adv. 2017;1(18):1375-1388. identified rs2301612 as one of the coding variants in the top independent LD block at the ADAMTS13 locus that collectively explain 20% of plasma ADAMTS13 variance in 3,244 healthy individuals.

The Evidence

The clinical relevance of the G allele was examined directly in Warlo et al. 202244 Warlo et al. 2022
Genetic Variation in ADAMTS13 is Related to VWF Levels, Atrial Fibrillation and Cerebral Ischemic Events. Eur Heart J Suppl. 2022. — a study of 1,000 patients with chronic coronary syndrome followed for 2 years (106 clinical endpoints). The 1342G-allele (rs2301612 G) was associated with significantly higher rates of prior atrial fibrillation (P=.016) and prior cerebral ischemic events (P=.030). Notably, heterozygous CG carriers — not GG homozygotes — experienced more 2-year clinical endpoints than either homozygous group (P=.028). The same study found the SNPs did not measurably affect ADAMTS13 levels themselves, suggesting the mechanism operates through altered ADAMTS13 substrate-binding efficiency or interaction with co-occurring variants rather than gross protein concentration.

At the pathway level, higher genetically determined ADAMTS13 activity is protective: a Mendelian randomization study55 Mendelian randomization study
Schooling CM et al. Atherosclerosis. 2019. using ADAMTS13 genetic instruments found that higher ADAMTS13 activity was inversely associated with ischemic heart disease (OR 0.91 per effect size, 95% CI 0.86–0.97), supporting a causal role for the ADAMTS13–VWF axis in coronary disease. The Rotterdam Study66 Rotterdam Study
Sonneveld MA et al. J Thromb Haemost. 2016;14:2114-2120. (5,688 elderly participants, 456 CHD events) found that the lowest ADAMTS13 activity quartile carried HR 1.42 (95% CI 1.07–1.89) for incident CHD independent of VWF levels and traditional risk factors.

ClinVar classifies the isolated Q448E G allele as Benign/Likely benign for Upshaw-Schulman syndrome (VCV000242806, criteria provided, multiple submitters, no conflicts) — consistent with its high population frequency (~40% in Europeans). The pathogenic ClinVar entry (VCV000005813) refers specifically to the compound haplotype of Q448E + C508Y on the same chromosome in a TTP patient, not to Q448E in isolation.

Practical Actions

For G-allele carriers — especially CG heterozygotes who showed the strongest clinical endpoint signal in Warlo et al. — the most important actionable step is awareness of the VWF-ADAMTS13 axis and elimination of known ADAMTS13-suppressing behaviors. Tobacco smoking is the largest modifiable environmental factor reducing plasma ADAMTS13 (Ma et al. 2017). The G allele's context-dependent enzymatic effects make the genetic background especially relevant when additional ADAMTS13-impairing variants are present.

Interactions

Q448E sits within the same LD block as rs28673647, the top intronic ADAMTS13 activity variant. The compound effect of Q448E with the pathogenic R1336W mutation (Plaimauer 2006) demonstrates that coding variants in this gene can combine destructively — an important consideration when genetic testing reveals multiple ADAMTS13 variants. Co-occurring VWF-elevating variants (e.g., rs1063856) create an adverse VWF:ADAMTS13 ratio that amplifies thrombotic risk from any ADAMTS13-impairing variant. The 15-fold DVT risk observed with combined low ADAMTS13 activity and high VWF levels (Pagliari et al. 2021, Thromb Res) underscores the importance of interpreting rs2301612 alongside VWF status.

Genotype Interpretations

What each possible genotype means for this variant.

CC Q448 Reference Normal

Standard ADAMTS13 Q448 genotype — reference form of the VWF-cleaving enzyme

ClinVar classifies Q448E (the G allele) as Benign/Likely benign in isolation, meaning the reference Q448 (CC) genotype has no established pathological significance. Functional studies (Plaimauer et al. 2006) show Q448 (the reference form) as the baseline against which Q448E's context-dependent effects are measured.

The CC genotype is not associated with elevated VWF-related thrombotic risk from this variant. Your overall ADAMTS13 activity is determined by other variants in the gene (such as rs28673647 and rs3739893) and by lifestyle factors including tobacco smoking.

CG Q448E Heterozygous Intermediate

One G allele (Q448E) — context-dependent ADAMTS13 modifier; heterozygotes showed elevated cardiovascular event rates in coronary syndrome patients

The heterozygote finding from Warlo et al. 2022 is notable because the CG group — not the GG homozygotes — showed the strongest clinical endpoint signal. This non-additive pattern is consistent with Q448E's context-dependent behavior described by Plaimauer et al. 2006: in certain genetic backgrounds, one copy of Q448E can act as a modifier that shifts ADAMTS13 function in ways that are not simply dose-dependent. The SNPs in this study did not significantly alter ADAMTS13 plasma levels, pointing to altered substrate-binding or functional efficiency rather than protein quantity as the likely mechanism.

The cardiovascular associations (AF, cerebral ischemic events) reflect the broader ADAMTS13-VWF axis: impaired VWF cleavage allows large multimers to promote platelet aggregation in the atria and cerebral microvasculature. The evidence level is moderate — replicated in a single large clinical cohort, with biological plausibility from functional studies, but not yet clinical-guideline grade.

GG Q448E Homozygous High Risk

Two G alleles (Q448E/Q448E) — homozygous coding variant in the ADAMTS13 spacer domain

The population-level cardiovascular risk data from Warlo et al. 2022 showed that the heterozygous CG group — not GG homozygotes — had the clearest clinical endpoint signal. This non-additive pattern may reflect dosage compensation or distinct functional consequences at two copies versus one. GG individuals carry the modified enzyme at both alleles and are most susceptible to the enzyme activity consequences if additional ADAMTS13-impairing variants (e.g., rare pathogenic mutations or the strongly negative rs3739893) are co-inherited.

ClinVar classifies isolated Q448E as Benign/Likely benign (VCV000242806) based on high population frequency. The pathogenic TTP designation (VCV000005813) applies specifically to the compound haplotype Q448E + C508Y, where the two mutations together create severe functional impairment — not to Q448E alone.

Full ADAMTS13 deficiency (activity <10%) causes thrombotic thrombocytopenic purpura (TTP). Q448E in isolation does not approach this threshold, but homozygous carriers with concurrent TTP-predisposing mutations face a modified genetic background that can lower the threshold for clinically significant ADAMTS13 impairment.