In vivo modulation of a dominant‐negative variant in mouse models of von Willebrand disease type 2A

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Unlabelled Box AbstractBackgroundTreatment options for patients suffering from von Willebrand disease (VWD) are limited. Von Willebrand factor (VWF) is a polymeric protein that undergoes regulated dimerization and subsequent multimerization during its biosynthesis. Numerous heterozygous variants within the VWF gene display a dominant‐negative effect and result in severe VWD. Previous studies have suggested that preventing the assembly of wild‐type and mutant heteropolymers using siRNAs may have beneficial effects on VWF phenotypes in vitro. ObjectivesTo study heterozygous dominant‐negative variants in vivo, we developed a mouse model of VWD‐type 2A and tested two independent strategies to modulate its detrimental effect. MethodsThe p.P1127_C1948delinsR deletion/variant, causing defective VWF multimerization, was expressed in mice as a model of VWD‐type 2A variant. Two corrective strategies were applied. For the first time in a mouse model of VWD, we applied siRNAs selectively inhibiting translation of the mutant transcripts and we combined the VWD‐type 2A deletion with the Cys to Arg substitution at position 2773, which is known to prevent dimerization. ResultsThe RNA silencing approach induced a modest but consistent improvement of the VWF multimer profile. However, due to incomplete efficiency, the dominant‐negative effect of the original variant could not be completely prevented. In contrast, the DNA approach resulted in increased antigen levels and restoration of a normal multimer profile. ConclusionsOur data showed that preventing the detrimental impact of dominant‐negative VWF variants by independent molecular mechanisms has beneficial consequences in vivo, in mouse models of dominant VWD.