Characterization of large in-frame von Willebrand factor deletions highlights differing pathogenic mechanisms.

Abstract

Copy number variation (CNV) is known to cause all von Willebrand disease (VWD) types, although the associated pathogenic mechanisms involved have not been extensively studied. Notably, in-frame CNV provides a unique opportunity to investigate how specific von Willebrand factor (VWF) domains influence the processing and packaging of the protein. Using multiplex ligation-dependent probe amplification, this study determined the extent to which CNV contributed to VWD in the Molecular and Clinical Markers for the Diagnosis and Management of Type 1 von Willebrand Disease cohort, highlighting in-frame deletions of exons 3, 4-5, 32-34, and 33-34. Heterozygous in vitro recombinant VWF expression demonstrated that, although deletion of exons 3, 32-34, and 33-34 all resulted in significant reductions in total VWF (P < .0001, P < .001, and P < .01, respectively), only deletion of exons 3 and 32-34 had a significant impact on VWF secretion (P < .0001). High-resolution microscopy of heterozygous and homozygous deletions confirmed these observations, indicating that deletion of exons 3 and 32-34 severely impaired pseudo-Weibel-Palade body (WPB) formation, whereas deletion of exons 33-34 did not, with this variant still exhibiting pseudo-WPB formation similar to wild-type VWF. In-frame deletions in VWD, therefore, contribute to pathogenesis via moderate or severe defects in VWF biosynthesis and secretion.

• Authors: Ashley Cartwright, Simon J Webster, Annika de Jong, Richard J Dirven, Lisa D S Bloomer, Ahlam M Al-Buhairan, Ulrich Budde, Christer Halldén, David Habart, Jenny Goudemand, Ian R Peake, Jeroen C J Eikenboom, Anne C Goodeve, Daniel J Hampshire
• Journal: Blood advances (Blood Adv) Vol. 4 Issue 13 Pg. 2979-2990 (07 14 2020) ISSN: 2473-9537 [Electronic] United States
• PMID: 32609846 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: © 2020 by The American Society of Hematology.

Chemical References

• von Willebrand Factor

Topics

• DNA Copy Number Variations
• Humans
• Weibel-Palade Bodies
• von Willebrand Disease, Type 1
• von Willebrand Diseases (diagnosis, genetics)
• von Willebrand Factor (genetics)