title: Reduced von Willebrand factor secretion is associated with loss of Weibel-Palade body formation.
abstract: 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.
  
  
  OBJECTIVE
  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.
authors.affiliation: Department of Cellular Therapy and Hematology, San Bortolo Hospital, Vicenza, Italy. castaman@hemato.ven.it
authors.forename: G
authors.initials: G
authors.lastname: Castaman
authors.forename: S H
authors.initials: SH
authors.lastname: Giacomelli
authors.forename: P M
authors.initials: PM
authors.lastname: Jacobi
authors.forename: T
authors.initials: T
authors.lastname: Obser
authors.forename: U
authors.initials: U
authors.lastname: Budde
authors.forename: F
authors.initials: F
authors.lastname: Rodeghiero
authors.forename: R
authors.initials: R
authors.lastname: Schneppenheim
authors.forename: S L
authors.initials: SL
authors.lastname: Haberichter
mesh_terms: D003094:Collagen / Q000378:metabolism; D015536:Down-Regulation; D005455:Fluorescent Antibody Technique; D020022:Genetic Predisposition to Disease; D057809:HEK293 Cells; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D018613:Microscopy, Confocal; D020125:Mutation, Missense; D010641:Phenotype; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D014162:Transfection; D020302:Weibel-Palade Bodies / Q000378:metabolism* / Q000473:pathology*; D056725:von Willebrand Disease, Type 1 / Q000097:blood / Q000235:genetics / Q000473:pathology*; D014841:von Willebrand Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor; D003094:Collagen