OBJECTIVETo disclose the impact of Trp1707Ser mutation on the binding mechanism of rFVIII light chain (rFVIII LC) with VWF.

METHODSUsing long-chain PCR technique, we constructed rFVIII LC plasmids of both wild type and Trp1707Ser mutant type. BL21 competent cells were used for protein expression. Gradient renaturation was employed to refold protein. SDS-PAGE and Western blot were performed to identify the molecular weight of expressed protein. GST-Sefinose was used for protein purification and surface plasmon resonance (SPR) was employed to detect binding of B-domain-deleted rFVIII (BDD-rFVIII), wild and mutant rFVIII LC with VWF, respectively.

RESULTSThe results of SDS-PAGE and Western blot showed a molecular weight of 110×10(3) of expressed proteins, which were consistent with objective proteins. The expression quantity of wild type was higher than that of mutant type. A concentration-dependent combination of the 3 testing proteins with VWF was found. The KD value of BDDrFVIII (12.2) was lower than that of both rFVIII LCs (wild type 48.9 and mutant type 46.3), whereas there was no discrepancy between wild rFVIII LC and mutant rFVIII LC.

CONCLUSIONTrp1707Ser mutation didn't impact the binding of rFVIII LC expressed by BL21 competent cells with VWF. The heavy chain played a more important role in impacting the binding of FVIII with VWF.

Mutation ; von Willebrand Factor ; genetics

Objective of this study was to identify gene mutation involved in a patient with type 2A von Willebrand disease (vWD). The bleeding time, vWF:Ag, FVIII:C, RIPA and multimeric assay were used for phenotypic diagnosis. All of the 52 exons and the exon-intron boundaries of vWF gene were amplified by polymerase chain reaction (PCR) and direct sequencing was carried out. The results indicated that the levels of vWF:Ag, FVIII:C and RIPA decreased in this patient, the vWF multimer with high and intermediate molecular weight was absent in plasma. The sequencing of genomic DNA revealed a C4738G (L1580V) missense mutation in the vWF gene from the patient. In conclusion, the C4738G (L1580V) missense mutation effecting the form of vWF multimer was responsible to molecular mechanism in this patient with vWD.
Adult ; Humans ; Male ; Mutation, Missense ; von Willebrand Disease, Type 2 ; genetics ; von Willebrand Factor ; analysis ; genetics

OBJECTIVETo study the influence of C-terminal domain of ADAMTS13 on its cleaving activity.

METHODSThe full-length wild-type (WT) and C-terminal domain truncated type (TT, TSP8 + CUB domains were deleted) of human ADAMTS13 recombinant protein were transfected into and permanent expressed on Hela cells. Western blot and R-CBA were used to directly detect the activities of the two recombinant proteins under the static and stressed condition respectively. ELISA was used to compare the binding abilities of the two proteins by coating with vWF.

RESULTSThe recombinant proteins were identified by Western blot with anti-his-tag or anti-ADAMTS13 antibodies. With pretreatment of 1.5 M urea, the enzyme activity of TT was significantly higher than that of WT, and so did in binding ability with vWF While, only WT could cleave vWF under high stress.

CONCLUSIONThe distal carboxyl-terminal TSP8 together with CUB domains of ADAMTS13 may affect the enzyme activity by regulating the binding of ADAMTS13 to vWF in different conditions, and they are very important for the enzyme activity under high stress force condition.

Galium ; Humans ; Recombinant Proteins ; metabolism ; Transfection ; von Willebrand Factor ; genetics

A 10-year-old male patient affected by type 2 von Willebrand disease (vWD) and his family members were investigated by hemostatic and molecular genetic studies. The propositus, who experienced frequent bleeding episodes, was characterized by a normal level of von Willebrand factor (vWF) antigen (54%), reduced vWF ristocetin cofactor activity (5%), decreased factor VIII clotting activity (25%) and absent high molecular weight multimers in the plasma. An exon 28 fragment coding for the A1 and A2 domains was amplified by polymerase chain reaction and sequenced. We found a heterozygous mutation (G4022A), producing an additional PstI restriction site, which resulted in the substitution of Arg578Gln. Family studies, including the parents and a brother, were negative for this mutation and vWF abnormalities were not observed. We confirmed that G to A mutation in the region of the platelet glycoprotein Ib binding domain of vWF causes the qualitative type 2 defect in von Willebrand disease.
Alanine/genetics* ; Case Report ; Child ; Glycine/genetics* ; Human ; Male ; Point Mutation* ; von Willebrand Disease/genetics* ; von Willebrand Factor/genetics*

OBJECTIVETo analyze the phenotype and genotype of two Chinese pedigrees with von Willebrand diseases, and to investigate the molecular pathogenesis.

METHODSBleeding time (BT), activated partial thromboplastin time (APTT), ristocetin-induced platelet aggregation (RIPA), von Willebrand factor-ristocetin cofactor (vWF:Rco), von Willebrand factor antigen (vWF:Ag), von Willebrand factor activity (vWF:A), von Willebrand factor collagen binding assay (vWF:CB) and multimer analysis were used for phenotype diagnosis. DNA was extracted. All of the 52 exons and exon-intron bounda ries of the VWF gene were amplified with polymerase chain reaction(PCR) and analyzed by direct sequencing.

RESULTSAPTT and BT were prolonged. Plasma RIPA, vWF:Rco, vWF:Ag, vWF:A and vWF:CB was significantly decreased. No VWF multimer can be found by plasma VWF multimer analysis. Homozygous insertional mutation g.82888_82889insCATG in exon 17 was found in proband A. Compound heterozygous mutations g.94865 G to A (Trp856stop) in exon 20 and g.110698_110699delinsG in exon 28 were found in proband B.

CONCLUSIONHomozygous insertional mutation g.82888_82889insCATG and compound heterozygous mutations g.94865G to A(Trp856X) and g.110698_110699delinsG probably have respectively induced type 3 von Willebrand diseases in the two probands.

Adolescent ; Female ; Genotype ; Humans ; Male ; Mutation ; Pedigree ; Phenotype ; von Willebrand Disease, Type 3 ; genetics ; von Willebrand Factor ; genetics

BACKGROUND: von Willebrand disease (VWD), characterized by quantitative or qualitative defects of von Willebrand factor (VWF), is the most common inheritable bleeding disorder. Data regarding the genetic background of VWD in Korean patients is limited. To our knowledge, this is the first comprehensive molecular genetic investigation of Korean patients with VWD. METHODS: Twenty-two unrelated patients with VWD were recruited from August 2014 to December 2017 (age range 28 months–64 years; male:female ratio 1.2:1). Fifteen patients had type 1, six had type 2, and one had type 3 VWD. Blood samples were collected for coagulation analyses and molecular genetic analyses from each patient. Direct sequencing of all exons, flanking intronic sequences, and the promoter of VWF was performed. In patients without sequence variants, multiplex ligation-dependent probe amplification (MLPA) was performed to detect dosage variants. We adapted the American College of Medical Genetics and Genomics guidelines for variant interpretation and considered variants of uncertain significance, likely pathogenic variants, and pathogenic variants as putative disease-causing variants. RESULTS: VWF variants were identified in 15 patients (68%): 14 patients with a single heterozygous variant and one patient with two heterozygous variants. The variants consisted of 13 missense variants, one small insertion, and one splicing variant. Four variants were novel: p.S764Efs*16, p.C889R, p.C1130Y, and p.W2193C. MLPA analysis in seven patients without reportable variants revealed no dosage variants. CONCLUSIONS: This study revealed the spectrum of VWF variants, including novel ones, and limited diagnostic utility of MLPA analyses in Korean patients with VWD.
Exons ; Genetic Background ; Genetics, Medical ; Genomics ; Hemorrhage ; Humans ; Introns ; Korea ; Molecular Biology ; Multiplex Polymerase Chain Reaction ; von Willebrand Disease, Type 3 ; von Willebrand Diseases ; von Willebrand Factor

Congenital thrombotic thrombocytopenic purpura, also known as Upshaw-Schulman syndrome, is a rare autosomal recessive genetic disorder. The main pathogenesis is homozygous or compound heterozygous variants of von Willebrand factor lyase (ADAMTS13) gene mapped to chromosome 9q34, which may result in severe lack of ADAMTS13 which cleaves von Willebrand factor (vWF) multimers in the plasma and increase the risk of microvascular thrombosis, leading to various complications. The advance of research on the pathogenesis of cTTP, recombinant human ADAMTS13 and gene therapy have made breakthroughs which may lead to cure of cTTP. This article has provided a review for the latest progress made in the diagnosis and treatment of cTTP.
ADAM Proteins/genetics* ; ADAMTS13 Protein/genetics* ; Homozygote ; Humans ; Purpura, Thrombotic Thrombocytopenic/therapy* ; von Willebrand Factor/genetics*

OBJECTIVE: To investigate the biological function of Cysteine rich (CysR) domain of a disintegrin and metalloprotease with thrombospondin type 1 repeats-13 (ADAMTS13) on cleavage of von Willebrand factor (vWF) and provide experimental evidence for exploring the pathogenesis of thrombotic thrombocytopenic purpura (TTP). METHODS: The six amino acids (EDGTLS) in ADAMTS13 CysR domain were point mutated one by one, and the mutant ADAMTS13 proteins were expressed and purified. The cleavage products of vWF polymer by wild-type or mutant ADAMTS13 under denaturing condition or shear stress were separated by 1% SeaKem HGT agarose gel and detected by Western blot. RESULTS: The mutant ADAMTS13 plasmids (M1: Glu515Ala; M2: Asp516Ala; M3: Gly517Ala; M4: Thr518Ala; M5: Leu519Ala; M6: Ser520Ala) were successfully constructed and the proteins of wild-type and mutant ADAMTS13 were purified. Wild-type ADAMTS13 almost completely cleaved the vWF polymer under denaturing condition, while the cleavage activity of M1 mutant was significantly reduced in the same condition (P<0.01). The cleavage activity of M1 mutant of ADAMTS13 was also significantly reduced compared with that of the wild-type under shear stress (P<0.01). The activity of M1 mutant to cleave the FRETS-vWF73 was dramatically reduced compared with that of wild-type ADAMTS13. However, the binding ability of M1 mutant to vWF was similar with that of wild-type ADAMTS13. CONCLUSION The CysR domain of ADAMTS13 plays an important role in the digestion of vWF under denaturing condition and shear stress. The Glu515 amino acid residue might be an important site for substrate recognition.
ADAM Proteins ; ADAMTS13 Protein/genetics* ; Humans ; Purpura, Thrombotic Thrombocytopenic/genetics* ; von Willebrand Factor/genetics*

OBJECTIVETo investigate the susceptibility of von Willebrand factor (VWF) type 2A mutant A1500E to proteolysis by metalloprotease ADAMTS13 and to provide the direct supports for the pathogenesis of VWF mutation A1500E responsible for von Willebrand disease (VWD) type 2A.

METHODSRecombinant wild-type VWF (WT-VWF) and A1500E mutant VWF transiently expressed on transfected HeLa cell lines. Expression media were collected and concentrated, then cleaved directly by recombinant ADAMTS13 (rADAMTS13). Compared with WT-VWF, the susceptibility of A1500E mutant VWF to proteolysis by ADAMTS13 was analyzed using SDS-agarose gel VWF multimers analysis.

RESULTSIn vitro the expression of VWF:Ag in the supernatants of WT-VWF and A1500E mutant VWF were 1.10 U/ml and 0.78 U/ml, respectively, while VWF:Ag in cells lysates of A1500E mutant VWF was 90.6% of that of WT-VWF. The SDS-agarose gel VWF multimers analysis showed that there were no differences between WT-VWF and A1500E mutant VWF. The A1500E mutant VWF could be efficiently cleaved by ADAMTS13 under static condition without denaturants such as urea and guanidine HCl. VWF multimeric analysis showed that high and intermediate molecular weight multimers dramatically decreased while low molecular weight multimers obviously increased. Conversely, WT-VWF could not be cleaved by ADAMTS13 under the same condition.

CONCLUSIONThe A1500E mutation resulted in VWF more susceptible to ADAMTS13-dependent proteolysis, which belonged to VWD type 2A group 2 mutation.

ADAM Proteins ; genetics ; metabolism ; ADAMTS13 Protein ; Genotype ; HeLa Cells ; Humans ; Hydrolysis ; Mutation ; Recombinant Proteins ; genetics ; metabolism ; von Willebrand Disease, Type 2 ; genetics ; metabolism ; von Willebrand Factor ; genetics

Type 2N von Willebrand disease (vWD) can be confused with hemophilia A due to decreased factor VIII levels and a bleeding tendency, and differential diagnosis is of importance for providing the optimal treatment and genetic counseling. For the accurate diagnosis of type 2N vWD, von Willebrand Factor (vWF) function tests, multimer assay and gene mutation analysis are needed. The patient was a 38-yr-old Nepalese woman with a history of bleeding manifestations from childhood, such as hemarthrosis, intramuscular hematoma, and menorrhagia. Family history revealed that her mother and elder brothers also had bleeding manifestations from childhood. When she had a laparotomy in 1991, she was diagnosed as hemophilia A with factor VIII level of 3.6% and was transfused with whole blood, factor VIII and cryoprecipitates. In June 2007, she was admitted to our hospital for further evaluation of bleeding tendency. Blood tests revealed normal CBC; bleeding time, 2 min; PT, 14.9 sec (11-14 sec); aPTT, 51.2 sec (24-38 sec); and factor VIII, 4.9% (50-150%). The prolonged aPTT was corrected by 1:1 mixing test to the levels of 106% and 84%, respectively, before and after 2 hr-incubation at 37degrees C. No abnormalities were found in the vWF antigen level (71.3%), ristocetin cofactor assay (130.4%), and multimer assay. Direct DNA sequencing of the VWF gene revealed homozygous missense mutation located in exon 19, c.2446C>T (p.Arg816Trp), confirming the diagnosis of type 2N vWD.
Adult ; Amino Acid Substitution ; Asian Continental Ancestry Group/genetics ; Base Sequence ; Female ; Genotype ; Homozygote ; Humans ; Nepal ; von Willebrand Disease/blood/*diagnosis/genetics ; von Willebrand Factor/analysis/*genetics