Fibronectin binding to von Willebrand factor occurs via the A1 domain

Whole exome sequencing identifies a novel variant in the COL12A1 gene in a family with Ullrich congenital muscular dystrophy 2

BACKGROUND

Mutations within the COL12A1 gene have been linked with the onset of congenital Ullrich muscular dystrophy 2 (UCMD2) and Bethlem myopathy. The severity of the symptoms exhibited is dependent on the mutation's type and whether it is heterozygous or homozygous.

METHODS

We used whole-exome sequencing to identify disease-causing variants in a nine-year-old Iranian patient who had weakness, joint contractures, delayed motor development, and other symptoms. We confirmed the pathogenicity of the identified variant using in silico tools and verified its novelty using various databases. We also performed a co-segregation study and confirmed the presence of the variant in the patient's parents by Sanger sequencing.

RESULTS

Our analysis identified a novel homozygous missense variant in the affected patient in COL12A1 (c.8828 C > T; p.Pro2943Leu). This is the second reported family with UCMD2 caused by a mutation in COL12A1. Our findings confirm that this mutation results in significantly more severe symptoms than Bethlem myopathy.

CONCLUSION

Our investigation contributes to the expanding body of evidence that links mutations in COL12A1 with UCMD2. Our findings confirm that the homozygous mutation in COL12A1 caused this condition and suggest that genetic testing for this mutation may be useful for diagnosing patients with this disease.

Staphylococcus aureus iron-regulated surface determinant B (IsdB) protein interacts with von Willebrand factor and promotes adherence to endothelial cells

Staphylococcus aureus is the cause of a spectrum of diseases in humans and animals. The molecular basis of this pathogenicity lies in the expression of a variety of virulence factors, including proteins that mediate adherence to the host plasma and extracellular matrix proteins. In this study, we discovered that the iron-regulated surface determinant B (IsdB) protein, besides being involved in iron transport and vitronectin binding, interacts with von Willebrand Factor (vWF). IsdB-expressing bacteria bound to both soluble and immobilized vWF. The binding of recombinant IsdB to vWF was blocked by heparin and reduced at high ionic strength. Furthermore, treatment with ristocetin, an allosteric agent that promotes the exposure of the A1 domain of vWF, potentiates the binding of IsdB to vWF. Both near-iron transporter motifs NEAT1 and NEAT2 of IsdB individually bound recombinant A1 domain with K_D values in the micromolar range. The binding of IsdB and adhesion of S. aureus expressing IsdB to monolayers of activated endothelial cells was significantly inhibited by a monoclonal antibody against the A1 domain and by IsdB reactive IgG from patients with staphylococcal endocarditis. This suggests the importance of IsdB in adherence of S. aureus to the endothelium colonization and as potential therapeutic target.

Erratum:

[This corrects the article DOI: 10.1002/rth2.12534.].

Commonly used anti-von Willebrand factor antibody for multimer analysis cross-reacts with fibronectin, which is difficult to distinguish from von Willebrand factor

Von Willebrand factor (VWF) is a 500- to 15 000-kDa multimeric protein circulating in the blood. When VWF has a higher molecular weight, its hemostatic activity is greater. The size distribution of VWF multimers is usually analyzed by SDS-agarose gel electrophoresis followed by immunoblotting. We found that the most commonly used anti-VWF antibody cross-reacted with fibronectin in VWF multimer analysis. In addition, since the apparent molecular weights of VWF and fibronectin are almost identical, these molecules were difficult to distinguish by SDS-polyacrylamide gel electrophoresis followed by immunoblotting. Cross-reactivity between the anti-VWF antibody and fibronectin was inhibited by pretreating the antibody with fibronectin-coated plates. To obtain accurate data using anti-VWF antibodies, it is necessary to be aware of the possibility of cross-reactivity with fibronectin.