rs61748497 — VWF C1060R

VWF C1060R — When the Clotting Carrier Cannot Hold Its Cargo

Von Willebrand factor (VWF) does two jobs in haemostasis: it captures platelets at sites of vascular injury, and it acts as a molecular chaperone that binds and shields coagulation factor VIII¹¹ factor VIII
the clotting protein deficient in haemophilia A; VWF keeps it from being degraded in the bloodstream before it is needed from premature proteolytic clearance. The rs61748497 variant — encoding the p.Cys1060Arg substitution in the D3 domain — specifically cripples the second job. VWF quantity is normal, platelet plug formation is intact, but FVIII levels fall because the carrier protein can no longer hold its cargo. The result is a condition classified as von Willebrand disease type 2N²² von Willebrand disease type 2N
named for Normandy, France, where the subtype was first described — a bleeding disorder that mimics haemophilia A but arises from a VWF gene defect rather than an FVIII gene defect.

The Mechanism

The VWF gene sits on the minus strand of chromosome 12p13.31. The rs61748497 variant is described as c.3178T>C on the coding strand (NM_000552.5), which corresponds to the plus-strand genomic change NC_000012.12:g.6025624A>G. The substitution converts codon 1060 from TGT (cysteine) to CGT (arginine) — p.Cys1060Arg. Cysteine residues frequently participate in disulphide bonds that maintain tertiary protein structure; the C1060 residue is located in the C8_3 subdomain of the D3 domain, a region critical for the three-dimensional architecture of the VWF-FVIII interaction interface.

Przeradzka et al. (2018)³³ Przeradzka et al. (2018)
Przeradzka MA et al. The D' domain of VWF requires the presence of the D3 domain for optimal factor VIII binding. Biochem J. 2018 used chemical footprinting mass spectrometry to demonstrate that C1060R induces conformational changes in the D3 domain that are quantitatively proportional to the reduction in FVIII binding affinity. The mutation does not simply remove a single contact point — it disrupts the overall fold of the D3 domain in a way that reduces the capacity of the neighbouring D' domain (the canonical FVIII binding site) to engage factor VIII effectively. The result is a FVIII binding capacity that ranges from severely reduced to completely absent depending on whether the patient carries one or two copies of the mutant allele.

The Evidence

The definitive characterization of C1060R comes from Hilbert et al. (2003)⁴⁴ Hilbert et al. (2003)
Hilbert L et al. Two novel mutations, Q1053H and C1060R, located in the D3 domain of VWF, are responsible for decreased FVIII-binding capacity. Br J Haematol. 2003;120(4):627-32, who identified the mutation in seven unrelated French families with type 2N VWD and confirmed its functional impact through site-directed mutagenesis and transient expression in COS-7 cells. C1060R was found in heterozygous, homozygous, and compound heterozygous states, with phenotypic severity tracking the number of mutant alleles. Its occurrence outside the originally described FVIII-binding tryptic fragment (D' domain, residues 764–1035) established that D3 domain integrity is independently required for FVIII binding.

The index description of a clinically important compound heterozygous case appears in Mazurier et al. (2002)⁵⁵ Mazurier et al. (2002)
Mazurier C et al. Factor VIII deficiency not induced by FVIII gene mutation in a female first cousin of two brothers with haemophilia A. Br J Haematol. 2002;119(2):390-2: a 20-year-old woman with reduced FVIII activity was initially thought to be an obligate carrier of the family's haemophilia A mutation. She was instead found to carry compound heterozygosity for Y357X (a VWF null allele, rs61754002) and C1060R. Her VWF antigen levels were very low due to the null allele, her VWF:FVIII binding was undetectable, and her FVIII activity was severely reduced — a phenotype indistinguishable from haemophilia A on conventional testing. This case illustrates the diagnostic trap: any female presenting with isolated FVIII deficiency should have VWF molecular testing before haemophilia A carrier status is assumed.

The 2021 ASH/ISTH/NHF/WFH diagnostic guidelines⁶⁶ 2021 ASH/ISTH/NHF/WFH diagnostic guidelines
James PD et al. ASH ISTH NHF WFH 2021 guidelines on the diagnosis of VWD. Blood Adv. 2021;5(1):280-300 specifically include a diagnostic algorithm for type 2N: low FVIII with normal or borderline VWF antigen and ristocetin cofactor activity is the laboratory signature. Confirmation requires a VWF:FVIII binding assay — a test that directly measures VWF's capacity to bind factor VIII at physiological conditions. Genetic testing (sequencing of VWF exons encoding the D' and D3 domains) is recommended alongside phenotypic assays because heterozygous carriers can present with borderline laboratory values, and accurate diagnosis is essential for correct treatment.

Practical Actions

The critical clinical point is that desmopressin (DDAVP) does not correct the type 2N defect. Desmopressin releases stored VWF from endothelial cells, temporarily raising VWF antigen and — secondarily — FVIII levels. But the released VWF still carries the C1060R mutation and cannot bind FVIII normally: within hours, FVIII levels fall back as unprotected factor VIII is cleared from circulation. For haemostasis in type 2N patients, only VWF/FVIII concentrate (which delivers functional FVIII directly alongside VWF) reliably restores haemostatic competence. The 2021 management guidelines⁷⁷ 2021 management guidelines
Connell NT et al. ASH ISTH NHF WFH 2021 guidelines on the management of VWD. Blood Adv. 2021;5(1):301-325 recommend VWF/FVIII concentrate as the treatment of choice for type 2N, targeting VWF activity and FVIII activity ≥0.50 IU/mL peri-operatively.

Heterozygous carriers may or may not have measurable clinical phenotypes, depending on FVIII levels. Some carriers have FVIII in the low-normal range (40–60 IU/dL) and are entirely asymptomatic; others fall below normal thresholds and have mild bleeding symptoms, particularly around surgery or childbirth.

Interactions

C1060R is most clinically significant in compound heterozygous combination with a VWF null allele — where one allele produces no VWF protein and the other produces VWF that cannot bind FVIII. The index case (Mazurier 2002) carried C1060R together with Y357X (rs61754002), a nonsense allele that produces no VWF at all. In that combination, VWF antigen is reduced (driven by the null allele), VWF:FVIII binding is abolished (driven by C1060R), and FVIII activity is critically low — a full phenotypic haemophilia A presentation in a VWF gene carrier. Any VWF null allele (type 3 disease allele) on the second chromosome would produce a similar compound effect.

Blood group O independently lowers VWF antigen by 15–25%, which may push a heterozygous C1060R carrier's effective FVIII levels further below the normal range and worsen clinical bleeding phenotype without affecting the molecular defect.