Expression of two type 2N von Willebrand disease mutations identified in exon 18 of von Willebrand factor gene

Abstract

SummaryType 2N von Willebrand disease (VWD) is characterized by a markedly decreased affinity of von Willebrand factor (VWF) for factor VIII (FVIII). The FVIII binding site has been localized within the first 272 amino acid residues of mature VWF, encoded by exons 18-23. Two substitutions in exon 18 of VWF gene, inducing candidate mutations Y795C and C804F were identified in the heterozygous state in two French patients who also displayed the frequent R854Q mutation in exon 20. Expression studies in Cos-7 cells showed that these abnormalities, which implicate cysteine residues, induced secretion, multimerization and FVIII binding defects of corresponding recombinant VWF. Results from transfection experiments with R854Q, performed to reproduce the hybrid VWF present in patient plasma, were in agreement with those obtained for patient's plasma VWF. These findings confirm the importance of the VWF D' domain in FVIII binding. In addition, this work shows that exon 18 should preferentially be sequenced in type 2N VWD patients when the frequent R854Q mutation in exon 20 has been excluded or detected in the heterozygous state.

Abnormal von Willebrand factor secretion, factor VIII stabilization and thrombus dynamics in type 2N von Willebrand disease mice

“…However, the severe murine R854Q VWF secretion defect in HEK 293 cells is in contrast to human R854Q VWF, which is secreted at ~100% of wild type in COS‐7 cells, ~50% of wild type in AtT‐20 cells and ~40% of normal from blood outgrowth endothelial cells (BOECs) . WPB or pseudo‐WPB formation of human R854Q VWF in patient‐derived BOECs, AltT‐20 and HEK 293 cells appears normal .…”

“…We first assessed the influence of our murine type 2N VWD variations on VWF synthesis and secretion. Collectively within published case studies, the VWF variant database and the Canadian VWD patient population, individuals homozygous for the R854Q variant have reported VWF:Ag between 41% and 122%, and between 15% and 125% for the R763G variant [11,19,[32][33][34][35][36][37][38]. Interestingly, the R854Q variant has been identified in approximately 1% of type 1 VWD families in three separate multicenter studies [11,36,37].…”

“…In vivo expression was induced via hydrodynamic tail vein injections of the murine VWF cDNA containing the type 2N VWD variants under the enhanced murine transthyretin (ET) promoter in VWF knockout (KO) C57BL/6 mice [23], which induces variable VWF expression. For all studies, VWF:Ag levels were measured by ELISA using rabbit antihuman VWF antibodies A0082 and P0226 (Dako) and [11,19,[32][33][34][35][36][37][38]. VWF, von Willebrand factor.…”

“… Data summarized from the von Willebrand disease (VWD) variant database (http://www.vwf.group.shef.ac.uk/vwd.html, Accessed December 2015) and cited literature . VWF, von Willebrand factor. …”

Maxillary pseudotumor as initial manifestation of von Willebrand disease, type 2: report of a rare case and literature review

“…3,6,7 Mutations of the VWF gene located in chromosome 12 p13.3 causing quantitative or qualitative abnormalities in VWF lead to von Willebrand disease (VWD). 6,8 VWD is the most common inherited bleeding disorder, with a reported prevalence of up to 1% in the general population. 9 Several distinct types of VWD have been identified on the basis of the phenotypic and genetic characteristics, and an updated classification system for VWD has been proposed.…”