BACKGROUND: von Willebrand disease (VWD) is caused by mutations in von Willebrand factor (VWF) that have different pathophysiologic effect in causing low plasma VWF levels. Type 1 VWD includes quantitative plasma VWF deficiency with normal VWF structure and function. OBJECTIVES: We report three novel type 1 VWF mutations (A1716P, C2190Y and R2663C) located in different VWF domains that are associated with reduced secretion and reduced formation of elongated Weibel-Palade body (WPB)-like granules. METHODS: Transient expression of recombinant mutant full-length VWF in 293 EBNA cells was performed and secretion, collagen binding and GpIb binding assessed in comparison with wild-type VWF. Expression was also examined in HEK293 cells that form WPB-like granules when transfected with wild-type VWF. RESULTS: Laboratory results and multimer analysis of plasma VWF was compatible with type 1 VWD. Expression experiments demonstrated slightly reduced VWF synthesis and drastically impaired secretion upon homozygous expression. In HEK293 cells, homozygous expression of A1716P and C2190Y VWF variants failed to form elongated WPB-like granules, while R2663C was capable of WPB-like granules. Heterozygous expression of VWF variants had a negative impact on wild-type VWF with a reduction in elongated WPB-like granules in co-transfected cells. CONCLUSIONS: Our results demonstrate that homozygous and heterozygous quantitative VWF deficiency caused by missense VWF mutations in different VWF domains can be associated with inability to form endothelial WPB-like granules.
BACKGROUND:von Willebrand disease (VWD) is caused by mutations in von Willebrand factor (VWF) that have different pathophysiologic effect in causing low plasma VWF levels. Type 1 VWD includes quantitative plasma VWF deficiency with normal VWF structure and function. OBJECTIVES: We report three novel type 1 VWF mutations (A1716P, C2190Y and R2663C) located in different VWF domains that are associated with reduced secretion and reduced formation of elongated Weibel-Palade body (WPB)-like granules. METHODS: Transient expression of recombinant mutant full-length VWF in 293 EBNA cells was performed and secretion, collagen binding and GpIb binding assessed in comparison with wild-type VWF. Expression was also examined in HEK293 cells that form WPB-like granules when transfected with wild-type VWF. RESULTS: Laboratory results and multimer analysis of plasma VWF was compatible with type 1 VWD. Expression experiments demonstrated slightly reduced VWF synthesis and drastically impaired secretion upon homozygous expression. In HEK293 cells, homozygous expression of A1716P and C2190YVWF variants failed to form elongated WPB-like granules, while R2663C was capable of WPB-like granules. Heterozygous expression of VWF variants had a negative impact on wild-type VWF with a reduction in elongated WPB-like granules in co-transfected cells. CONCLUSIONS: Our results demonstrate that homozygous and heterozygous quantitative VWF deficiency caused by missense VWF mutations in different VWF domains can be associated with inability to form endothelial WPB-like granules.
Authors: Hamideh Yadegari; Julia Driesen; Anna Pavlova; Arijit Biswas; Vytautas Ivaskevicius; Robert Klamroth; Johannes Oldenburg Journal: Haematologica Date: 2013-03-28 Impact factor: 9.941