| 1. |
- Cartwright, Ashley, et al.
(author)
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Characterization of large in-frame von Willebrand factor deletions highlights differing pathogenic mechanisms
- 2020
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In: Blood Advances. - 2473-9529 .- 2473-9537. ; 4:13, s. 2979-2990
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Journal article (peer-reviewed)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.
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| 2. |
- Cartwright, Ashley, et al.
(author)
-
Characterization of large in-frame von Willebrand factor deletions highlights differing pathogenic mechanisms
- 2020
-
In: Blood Advances. - : Elsevier BV. - 2473-9529 .- 2473-9537. ; 4:13, s. 2979-2990
-
Journal article (peer-reviewed)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.
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| 3. |
- Castaman, Giancarlo, et al.
(author)
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Response to desmopressin is influenced by the genotype and phenotype in type 1 von Willebrand disease (VWD): results from the European Study MCMDM-1VWD
- 2008
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 111:7, s. 3531-3539
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Journal article (peer-reviewed)abstract
- We have prospectively evaluated the biologic response to desmopressin in 77 patients with type 1 von Willebrand disease (VWD) enrolled within the Molecular and Clinical Markers for the Diagnosis and Management of type 1 VWD project. Complete response to desmopressin was defined as an increase of both ristocetin cofactor activity (VWF:RCo) and factor VIII coagulant activity (FVIII:C) to 50 IU/dL or higher and partial response as VWF: RCo or FVIII:C lower than 50 IU/dL after infusion, but at least 3-fold the basal level. Complete response was observed in 83% of patients; partial in 13%; and no response in 4%. Patients with some abnormality of VWF multimeric pattern had significantly lower basal FVIII:C and VWF, lower VWF:RCo/Ag ratio, and less complete responses to desmopressin than patients with a normal multimeric pattern (P =.002). Patients with mutations at codons 1130 and 1205 in the D'-D3 domain had the greatest relative increase, but shortest FVIII and VWF half-lives after infusion. Most partial and nonresponsive patients had mutations in the A1-A3 domains. Response to desmopressin in these VWD patients seemed to be associated with the location of the causative mutation. The presence of subtle multimeric abnormalities did not hamper potential clinically useful responses, as in typical type 1 VWD.
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| 4. |
- Castaman, Giancarlo, et al.
(author)
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The impact of bleeding history, von Willebrand factor and PFA-100 (R) on the diagnosis of type 1 von Willebrand disease: results from the European study MCMDM-1VWD
- 2010
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In: British Journal of Haematology. - : Wiley. - 0007-1048. ; 151:3, s. 245-251
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Journal article (peer-reviewed)abstract
- P>The relationships between the Platelet Function Analyzer (PFA)-100 and von Willebrand factor (VWF) levels and bleeding score (BS) were evaluated within a multicentre project on Molecular and Clinical Markers for the Diagnosis and Management of type 1 von Willebrand disease (MCMDM-1VWD). PFA-100 closure time, either with epinephrine (EPI) or adenosine diphosphate (ADP)-cartridges, was measured in 107 index cases, 105 affected and 71 unaffected family members, and 79 healthy controls. By regression analysis VWF levels were strongly related to both closure times, with a non-linear progression. In a multiple stepwise regression model, age- and sex-adjusted PFA-100 ADP and VWF ristocetin cofactor activity (VWF:RCo) were independently associated with BS. Most of the variation of BS was predicted by PFA-100 ADP and VWF:RCo alone. In the subgroup of patients with subtle abnormalities of the multimeric pattern, VWF was invariably reduced and closure time prolonged in almost all of them. Neither PFA-100 ADP nor EPI closure times appeared to significantly improve the diagnostic capability of VWF antigen (VWF:Ag) measurement. Thus, in an unselected population a normal PFA-100 would be useful to exclude VWD, but whether it could replace the more specific VWF assay in patients with significant mucocutaneous bleeding symptoms remains to be investigated prospectively.
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| 5. |
- Goodeve, Anne, et al.
(author)
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Phenotype and genotype of a cohort of families historically diagnosed with type 1 von Willebrand disease in the European study, Molecular and Clinical Markers for the Diagnosis and Management of Type 1 von Willebrand Disease (MCMDM-1VWD)
- 2007
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 109:1, s. 112-121
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Journal article (peer-reviewed)abstract
- Type 1 von Willebrand disease (VWD) is characterized by a personal and family history of bleeding coincident with reduced levels of normal plasma von Willebrand factor (VWF). The molecular basis of the disorder is poorly understood. The aims of this study were to determine phenotype and genotype and their relationship in patients historically diagnosed with type 1 VWD. Families were recruited in 9 European countries based on previous type 1 VWD diagnosis. Bleeding symptoms were recorded, plasma phenotype analyzed, and VWF mutation analysis performed in all index cases (ICs). Phenotypic and molecular analysis stratified patients into those with or without phenotypes suggestive of qualitative VWF defects (abnormal multimers) and with or without mutations. A total of 105 of 150 ICs (70%) had mutations identified. A subgroup with abnormal multimers (38% of ICs, 57 of 150) showed a high prevalence of VWF gene mutations (95% of ICs, 54 of 57), whereas in those with qualitatively normal VWF, fewer mutations were identified (55% of ICs, 51 of 93). About one third of the type I VWD cases recruited could be reconsidered as type 2. The remaining group could be considered "true" type 1 VWD, although mutations were found in only 55%.
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| 6. |
- Haberichter, Sandra L, et al.
(author)
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Identification of type 1 von Willebrand disease patients with reduced von Willebrand factor survival by assay of the VWF propeptide in the European study: Molecular and Clinical Markers for the Diagnosis and Management of Type 1 VWD (MCMDM-1VWD)
- 2008
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 111:10, s. 4979-4985
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Journal article (peer-reviewed)abstract
- The decreased survival of von Willebrand factor (VWF) in plasma has been implicated as a mechanism in a subset of type 1 von Willebrand disease (VWD) patients. We have previously reported that the ratio of plasma levels of VWF and its propeptide (VWFpp) can be used to identify patients with reduced VWF survival. In this study, we report the assay of VWFpp and VWF:Ag in 19 individuals recruited from 6 European centers within the MCMDM-1VWD study. Eight individuals had a VWF:Ag level less than 30 IU/dL. Seven of these patients had a robust desmopressin response and significantly reduced VWF half-life that was predicted by a markedly increased steady-state plasma VWFpp/VWF:Ag ratio. VWF mutations previously associated with reduced VWF survival were identified in each of the 7 individuals. Thus, a substantially increased ratio of steady-state VWFpp/ VWF:Ag predicted a reduced VWF half-life in patients with markedly decreased VWF:Ag levels. These data indicate that a reduced VWF survival is found in a sub-population of patients with type 1 VWD. The systematic assay of both plasma VWF and the VWF propeptide in moderately severe type 1 VWD patients may identify patients with a reduced VWF survival phenotype.
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| 7. |
- Mufti, Ahmad H, et al.
(author)
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The common VWF single nucleotide variants c.2365A>G and c.2385T>C modify VWF biosynthesis and clearance
- 2018
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In: Blood Advances. - 2473-9529 .- 2473-9537. ; 2:13, s. 1585-1594
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Journal article (peer-reviewed)abstract
- Plasma levels of von Willebrand factor (VWF) vary considerably in the general population and this variation has been linked to several genetic and environmental factors. Genetic factors include 2 common single nucleotide variants (SNVs) located in VWF, rs1063856 (c.2365A>G) and rs1063857 (c.2385T>C), although to date the mechanistic basis for their association with VWF level is unknown. Using genotypic/phenotypic information from a European healthy control population, in vitro analyses of recombinant VWF expressing both SNVs, and in vivo murine models, this study determined the precise nature of their association with VWF level and investigated the mechanism(s) involved. Possession of either SNV corresponded with a significant increase in plasma VWF in healthy controls (P < .0001). In vitro expression confirmed this observation and highlighted an independent effect for each SNV (P < .0001 and P < .01, respectively), despite close proximity and strong linkage disequilibrium between them both. The influence of c.2365A>G on VWF levels was also confirmed in vivo. This increase in VWF protein corresponded to an increase in VWF messenger RNA (mRNA) resulting, in part, from prolonged mRNA half-life. In addition, coinheritance of both SNVs was associated with a lower VWF propeptide-to-VWF antigen ratio in healthy controls (P < .05) and a longer VWF half-life in VWF knockout mice (P < .0001). Both SNVs therefore directly increase VWF plasma levels through a combined influence on VWF biosynthesis and clearance, and may have an impact on disease phenotype in both hemostatic and thrombotic disorders.
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| 8. |
- Mufti, Ahmad H, et al.
(author)
-
The common VWF single nucleotide variants c.2365A>G and c.2385T>C modify VWF biosynthesis and clearance
- 2018
-
In: Blood Advances. - : Elsevier BV. - 2473-9529 .- 2473-9537. ; 2:13, s. 1585-1594
-
Journal article (peer-reviewed)abstract
- Plasma levels of von Willebrand factor (VWF) vary considerably in the general population and this variation has been linked to several genetic and environmental factors. Genetic factors include 2 common single nucleotide variants (SNVs) located in VWF, rs1063856 (c.2365A>G) and rs1063857 (c.2385T>C), although to date the mechanistic basis for their association with VWF level is unknown. Using genotypic/phenotypic information from a European healthy control population, in vitro analyses of recombinant VWF expressing both SNVs, and in vivo murine models, this study determined the precise nature of their association with VWF level and investigated the mechanism(s) involved. Possession of either SNV corresponded with a significant increase in plasma VWF in healthy controls (P < .0001). In vitro expression confirmed this observation and highlighted an independent effect for each SNV (P < .0001 and P < .01, respectively), despite close proximity and strong linkage disequilibrium between them both. The influence of c.2365A>G on VWF levels was also confirmed in vivo. This increase in VWF protein corresponded to an increase in VWF messenger RNA (mRNA) resulting, in part, from prolonged mRNA half-life. In addition, coinheritance of both SNVs was associated with a lower VWF propeptide-to-VWF antigen ratio in healthy controls (P < .05) and a longer VWF half-life in VWF knockout mice (P < .0001). Both SNVs therefore directly increase VWF plasma levels through a combined influence on VWF biosynthesis and clearance, and may have an impact on disease phenotype in both hemostatic and thrombotic disorders.
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| 9. |
- Volkers, Peter, et al.
(author)
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Recombinant factor VIII products and inhibitor development in previously untreated patients with severe haemophilia A : Combined analysis of three studies
- 2019
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In: Haemophilia. - : Wiley. - 1351-8216 .- 1365-2516. ; 25:3, s. 398-407
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Journal article (peer-reviewed)abstract
- INTRODUCTION: Standard treatment of congenital haemophilia A is based on replacement therapy with coagulation factor VIII (FVIII) products. A major complication of FVIII therapy is the occurrence of IgG alloantibodies (inhibitors) that neutralize FVIII activity.AIM: The aim of the analysis was estimating the risk of high-titre inhibitor associated with the second-generation full-length product compared to third-generation full-length product and other recombinant FVIII (rFVIII).METHODS: We conducted a combined analysis of individual patient data from three large studies in previously untreated patients (PUPs) with severe haemophilia A.RESULTS: A total of 1109 PUPs were treated from 1993 to 2013 including 787 PUPs treated from 2004 onwards (primary analysis cohort). A total of 322 patients (29.0%) developed an inhibitor, of which 192 (17.3%) a high-titre inhibitor. In the primary analysis set, 29.9% of patients developed an inhibitor and 17.2% a high-titre inhibitor. The combined analysis indicated a lower risk of high-titre inhibitor development for the third-generation rFVIII product compared to the second-generation rFVIII product (primary analysis: adjusted hazard ratio (HR) = 0.72, 95% CI: 0.49 to 1.06). Adjusted HR for all inhibitor development was significantly lower for the third-generation product compared to the second-generation product.CONCLUSION: The trend of an increased risk of inhibitor development in PUPs for one recombinant product illustrates that extrapolation from one recombinant factor VIII product to other products might not be justified.
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