Secondary literature sources for the VWD domain

For each of the hand selected primary papers associated with the VWD domain, 100 neighbouring papers are retrieved from PubMed. If one of these neighbouring papers is referenced by more than two primary papers, it is shown in the table below.

Characterization of the von Willebrand factor gene (VWF) in von Willebrand disease type III patients from 24 families of Swedish and Finnish origin.

Zhang ZP, Blomback M, Egberg N, Falk G, Anvret M
Genomics. 1994; 21: 188-93

Twenty-four patients with von Willebrand disease type III were screened for mutations in the von Willebrand factor (VWF) gene using the PCR technique, followed by direct sequencing. More than 250 kb of genomic DNA were sequenced, including the promoter and coding regions (52 exons) of the VWF gene from 24 patients. In addition to the previously reported mutations of a single cytosine deletion in exon 18 and the nonsense mutations in exons 28, 32, and 45, nine new mutations were detected: two nonsense mutations in exons 15 and 16, one allele with a thymidine insertion in exon 14, one allele with a cytosine insertion in exon 28, one 20-bp deletion in exon 15, one mutation in the donor splice site of exon 43, and three missense mutations in exons 28, 49, and 51. Forty-two mutant chromosomes were identified (42/48); 11 probands are homozygous for the mutations, and 8 are compound heterozygous. In addition, a new subfamily of the Alu sequence in the promoter region and 10 new polymorphisms were identified.

The complete primary structure of type XII collagen shows a chimeric molecule with reiterated fibronectin type III motifs, von Willebrand factor A motifs, a domain homologous to a noncollagenous region of type IX collagen, and short collagenous domains with an Arg-Gly-Asp site.

Yamagata M, Yamada KM, Yamada SS, Shinomura T, Tanaka H, Nishida Y, Obara M, Kimata K
J Cell Biol. 1991; 115: 209-21

Extracellular matrix molecules are generally categorized as collagens, elastin, proteoglycans, or other noncollagenous structural/cell interaction proteins. Many of these extracellular proteins contain distinctive repetitive modules, which can sometimes be found in other proteins. We describe the complete primary structure of an alpha 1 chain of type XII collagen from chick embryonic fibroblasts. This large, structurally chimeric molecule identified by cDNA analysis combines previously unrelated molecular domains into a single large protein 3,124 residues long (approximately 340 kD). The deduced chicken type XII collagen sequence starts at the amino terminus with one unit of the type III motif of fibronectin, which is followed by one unit homologous to the von Willebrand factor A domain, then one more fibronectin type III module, a second A domain from von Willebrand factor, 6 units of type III motif and a third A domain, 10 consecutive units of type III motif and a fourth A domain, a domain homologous to the NC4 domain peptide of type IX collagen, and finally two short collagenous regions previously described as part of the partially sequenced collagen type XII molecule; an Arg-Gly-Asp potential cell adhesive recognition sequence is present in a hydrophilic region at the terminus of one collagenous domain. Antibodies raised to type XII collagen synthesized in a bacterial expression system recognized not only previously reported bands (220 kD et cetera) in tendons, but also bands with apparently different molecular sizes in fibroblasts and 4-d embryos. The antibodies stained a wide variety of extracellular matrices in embryos in patterns distinct from those of fibronectin or interstitial collagens. They prominently stained extracellular matrix associated with certain neuronal tissues, such as axons from dorsal root ganglia and neural tube. These studies identify a novel chimeric type of molecule that contains both adhesion molecule and collagen motifs in one protein. Its structure blurs current classification schemes for extracellular proteins and underscores the potentially large diversity possible in these molecules.

The propeptide of von Willebrand factor independently mediates the assembly of von Willebrand multimers.

Wise RJ, Pittman DD, Handin RI, Kaufman RJ, Orkin SH
Cell. 1988; 52: 229-36

The biosynthesis of von Willebrand Factor (vWF) by vascular endothelial cells involves a complex series of processing steps that includes proteolytic cleavage of a 741-residue propeptide and the assembly of disulfide-linked multimers. Using a model system in which experimentally altered vWF cDNAs are expressed in COS-1 cells, we have shown that the vWF propeptide contains determinants that govern the assembly of vWF multimers. Furthermore, the role of the propeptide (in the assembly process) does not require it to be a contiguous part of the pro-vWF primary structure, since independently expressed propeptide was shown to promote the assembly of mature vWF subunits into multimers. Pulse-chase experiments indicated that the independently expressed propeptide formed a transient association with the mature vWF subunit inside the cell. Thus, it appears that the vWF propeptide segment can act in "trans" to direct the assembly of disulfide-linked vWF multimers.

Expression of a human proprotein processing enzyme: correct cleavage of the von Willebrand factor precursor at a paired basic amino acid site.

Wise RJ, Barr PJ, Wong PA, Kiefer MC, Brake AJ, Kaufman RJ
Proc Natl Acad Sci U S A. 1990; 87: 9378-82

Intracellular proteolytic processing of precursor polypeptides is an essential step in the maturation of many proteins, including plasma proteins, hormones, neuropeptides, and growth factors. Most frequently, propeptide cleavage occurs after paired basic amino acid residues. To date, no mammalian propeptide processing enzyme with such specificity has been purified or cloned and functionally characterized. We report the isolation and functional expression of a cDNA encoding a propeptide-cleaving enzyme from a human liver cell line. The encoded protein, called PACE (paired basic amino acid cleaving enzyme), has structural homology to the well-characterized subtilisin-like protease Kex2 from yeast. The functional specificity of PACE for mediating propeptide cleavage at paired basic amino acid residues was demonstrated by the enhancement of propeptide processing of human von Willebrand factor when coexpressed with PACE in COS-1 cells.

Divergent fates of von Willebrand factor and its propolypeptide (von Willebrand antigen II) after secretion from endothelial cells.

Wagner DD, Fay PJ, Sporn LA, Sinha S, Lawrence SO, Marder VJ
Proc Natl Acad Sci U S A. 1987; 84: 1955-9

The intracellular site of cleavage of pro-von Willebrand factor subunit and the subsequent fate of the propolypeptide (von Willebrand antigen II) and of the mature von Willebrand factor (vWf) were investigated. Both the propolypeptide, which was found to be a homodimer of noncovalently linked subunits, and mature vWf were released from Weibel-Palade bodies of endothelial cells following stimulation with secretagogues. The stoichiometry of the two released proteins was essentially equimolar. This indicates that vWf and the propolypeptide were packaged into the Weibel-Palade bodies as one unit, pro-vWf, and that the proteolytic cleavage of pro-vWf is likely to be a post-Golgi event. The association of prosequences into dimers supports their hypothetical role in the multimerization process. After secretion, the two proteins were distributed differently, as based on the following observations. The propolypeptide did not associate with vWf in the culture medium, did not codistribute with vWf in the extracellular "patches of release" on stimulated endothelial cells, and was not detected in the endothelial cell extracellular matrix, which did contain vWf. Additionally, in contrast to vWf, the propolypeptide did not bind to the matrix of human foreskin fibroblasts. Since the propolypeptide does not associate with vWf and does not interact with extracellular matrices in vitro, it is highly unlikely that it would promote platelet adhesion to subendothelium in vivo.

Cell biology of von Willebrand factor.

Wagner DD
Annu Rev Cell Biol. 1990; 6: 217-46

Biogenesis of von Willebrand factor-containing organelles in heterologous transfected CV-1 cells.

Voorberg J, Fontijn R, Calafat J, Janssen H, van Mourik JA, Pannekoek H
EMBO J. 1993; 12: 749-58

Von Willebrand factor (vWF) is a multimeric protein involved in the adhesion of platelets to an injured vessel wall. vWF is synthesized by the endothelial cell and the megakaryocyte as a precursor protein (pro-vWF) that consists of four repeated domains, denoted D1-D2-D'-D3-A1-A2-A3-D4-B1-B2-B3-C1-C2. Previously, we have defined the domains on the pro-vWF molecule involved in dimerization as well as the domains involved in multimer assembly of vWF dimers. In the endothelial cell, part of the vWF multimers is stored in specialized organelles, the Weibel-Palade bodies. By using immunoelectron microscopy, we demonstrate that upon expression of full-length vWF cDNA, vWF-containing organelles are encountered in monkey kidney CV-1 cells that are morphologically similar to the endothelial-specific Weibel-Palade bodies. Expression in CV-1 cells of a series of vWF cDNA deletion mutants, lacking one or more domains, revealed that only those vWF mutant proteins that are able to assemble into multimers are encountered in dense-cored vesicles. Our data show that this process is independent of a particular domain on vWF and indicate that a 'condensed', multimeric vWF is required for targeting to the Weibel-Palade body.

Assembly and routing of von Willebrand factor variants: the requirements for disulfide-linked dimerization reside within the carboxy-terminal 151 amino acids.

Voorberg J, Fontijn R, Calafat J, Janssen H, van Mourik JA, Pannekoek H
J Cell Biol. 1991; 113: 195-205

The precursor protein of von Willebrand factor (pro-vWF) consists of four different repeated domains, denoted D1-D2-D'-D3-A1-A2-A3-D4-B1-B2-B3-C1-C2, followed by a carboxy-terminal region of 151 amino acids without obvious internal homology. Previously, we have shown the requirement of the domains D1, D2, D', and D3 of pro-vWF in the assembly of pro-vWF dimers into multimers. Here, we define the domains of vWF involved in dimerization, using deletion mutants of full-length vWF cDNA transiently expressed in monkey kidney COS-1 cells. It is shown that only the carboxy-terminal 151 amino acid residues of vWF are required for dimerization. In addition, by analyzing a construct, encoding only the carboxy-terminal 151 amino acids of vWF, we find that the formation of dimers is an event independent of other domains present on pro-vWF, such as the domains C1 and C2 previously suggested to be involved in dimerization. Furthermore, it is shown that a deletion mutant of vWF, lacking the carboxy-terminal 151 amino acid residues and thus unable to dimerize, is proteolytically degraded in the ER. In contrast, a mutant protein, composed only of the carboxy-terminal 151 amino acids of vWF, and able to dimerize, is transported from the ER in a similar fashion as wild-type vWF. The role of the ER in the assembly of vWF is discussed with regard to the data presented in this paper on the intracellular fate of several vWF mutant proteins.

Factor VIII and von Willebrand factor.

Vlot AJ, Koppelman SJ, Bouma BN, Sixma JJ
Thromb Haemost. 1998; 79: 456-65

RFLP for a human von Willebrand factor (vWF) cDNA clone, pvWF1100.

Verweij CL, Hofker M, Quadt R, Briet E, Pannekoek H
Nucleic Acids Res. 1985; 13: 8289-8289

Proteolytic cleavage of the precursor of von Willebrand factor is not essential for multimer formation.

Verweij CL, Hart M, Pannekoek H
J Biol Chem. 1988; 263: 7921-4

Monkey kidney cells (COS-1), transfected with full-length human von Willebrand factor (vWF) cDNA encoding the precursor of vWF (pro-vWF), mimic the characteristics of the biosynthesis and of the constitutive secretory pathway, displayed by cultured vascular endothelial cells. Such heterologous transfected cells are able to cleave pro-vWF, generating the propolypeptide and mature vWF, and to assemble pro-vWF dimers into a series of multimers, similarly to endothelial cells. Evidence is presented showing that proteolytic processing of pro-vWF by COS-1 cells occurs at the peptide bond between arginine and serine in the sequence Lys762-Arg763-Ser764, identical to endothelial cell-associated proteolysis. This conclusion stems from the observation that substitution of Arg763 by a glycine residue completely abolishes proteolytic processing. As a result, transfection of COS-1 with the mutant vWF-Gly763 cDNA does not significantly affect the multimeric organization of secreted vWF molecules. Consequently, we conclude that proteolytic processing of pro-vWF is not required for multimer formation. Pulse-chase labeling of COS-1 cells transfected with full-length vWF cDNA reveals pro-vWF exclusively in cell lysates, whereas both pro-vWF and mature vWF are encountered in the conditioned medium. These observations indicate that proteolytic processing of pro-vWF is a "late" event during intracellular routing of these molecules or may occur extracellularly.

Expression of variant von Willebrand factor (vWF) cDNA in heterologous cells: requirement of the pro-polypeptide in vWF multimer formation.

Verweij CL, Hart M, Pannekoek H
EMBO J. 1987; 6: 2885-90

Von Willebrand factor (vWF) is a multimeric plasma glycoprotein synthesized by vascular endothelial cells as a pre-pro-polypeptide with a highly repetitive domain structure, symbolized by the formula: (H)-D1-D2-D'-D3-A1-A2-A3-D4-B1-B2-B3-C1-C2-(OH) A heterologous expression system for the synthesis of recombinant vWF protein was developed, consisting of a monkey kidney cell line (COS-1), transfected with full-length vWF cDNA. This system was shown to mimic the constitutive secretory pathway of vWF in endothelial cells, since dimerization and multimerization occur similarly. To determine whether the pro-polypeptide, composed of the domains D1 and D2, is involved in vWF multimerization, a vWF cDNA was constructed that lacked the coding sequence for the pro-polypeptide. The mutant vWF protein, expressed by COS-1 cells transfected with this cDNA, did not assemble beyond the dimer stage. From this observation, we conclude that (i) dimerization does not involve the pro-polypeptide of pro-vWF and (ii) the presence of the pro-polypeptide, as part of pro-vWF, is obligatory for multimerization. It is argued that the interactions, required for interchain binding, are mediated by the D domains.

Construction of cDNA coding for human von Willebrand factor using antibody probes for colony-screening and mapping of the chromosomal gene.

Verweij CL, de Vries CJ, Distel B, van Zonneveld AJ, van Kessel AG, van Mourik JA, Pannekoek H
Nucleic Acids Res. 1985; 13: 4699-717

Von Willebrand Factor (vWF) mRNA was identified in fractionated polyA+ RNA preparations isolated from cultured human endothelial cells. Micro-injection of specific polyA+ RNA fractions in Xenopus laevis oocytes provoked the synthesis of a vWF-like product which could be detected with an immunoradiometric assay relying on Sepharose-linked monoclonal anti-vWF IgG and different radiolabeled monoclonal anti-vWF IgGs. A vWF-mRNA-containing polyA+ RNA preparation served as substrate for a size-selected cDNA-expression library of 60 000 colonies which was screened for the synthesis of antigens related to vWF, using polyclonal anti-vWF IgG and a second antibody conjugated with peroxidase. Eight positive colonies were detected of which two reacted strongly in the enzyme-linked assay. Immunoblotting of bacterial extracts of "expression clones" with a monoclonal anti-vWF IgG revealed polypeptides which size fits within the length of the cDNA insertions. Northern blotting of human endothelial RNA, employing fragments of vWF cDNA as probes, showed specific hybridization with a mRNA of about 9000 nucleotides. DNA-sequence analysis of a vWF-cDNA insertion revealed an open reading frame followed by a translation stopcodon. It is argued that the cDNA insertions encode the carboxy-terminal part of the vWF protein. vWF-cDNA probes were employed to map the von Willebrand factor gene on chromosome 12 using a panel of 35 human-rodent somatic cell hybrids.

Biosynthesis of human von Willebrand factor.

Verweij CL
Haemostasis. 1988; 18: 224-45

Endothelium forms the inner lining of all blood vessels and, as a consequence, is in direct contact with the blood. Because of this and the synthesis and secretion of hemostatic components, the endothelium is able to modulate coagulation and fibrinolysis. An important hemostatic factor synthesized by endothelial cells is the von Willebrand factor (vWF). vWF is a large plasma glycoprotein which promotes the adhesion of platelets to the vessel wall after a vascular injury. vWF is initially synthesized as a pre-pro-polypeptide. During its transport to the outside of the cell, the single-chain polypeptides are assembled into multimers. The pro-polypeptide can be cleaved and also be secreted. Free pro-polypeptide is identified as von Willebrand antigen II, a plasma glycoprotein of unknown function. Plasma vWF consists of a heterogenous series of multimers, composed of an apparently single-type glycoprotein subunit, linked together by disulfide bonds. The hemostatic potency of vWF was shown to increase with increasing multimer size. Therefore, the multimeric assembly of vWF is a crucial aspect in vWF biosynthesis. Furthermore, vWF synthesized by endothelial cells can either be secreted constitutively or stored and released upon stimulation of the endothelial cell. In this review, data are presented which contribute to the understanding of the biosynthetic pathway and complex processing which vWF has to undergo before it is secreted by the endothelial cell. These data have allowed a prediction of the sequential events underlying vWF biosynthesis, processing, multimer assembly, and secretion.

Homozygous type IIC von Willebrand's disease.

Uno H, Yamazaki T, Suzuki M, Matsuoka H, Yoshioka A, Saito H, Tsubouchi H
Int J Hematol. 1996; 63: 243-5

Cysteine-rich regions of pig gastric mucin contain von willebrand factor and cystine knot domains at the carboxyl terminal(1).

Turner BS, Bhaskar KR, Hadzopoulou-Cladaras M, LaMont JT
Biochim Biophys Acta. 1999; 1447: 77-92

In order to sequence the cysteine-rich regions of pig gastric mucin (PGM), we used our previously identified pig gastric mucin clone PGM-2A to screen a pig stomach cDNA library and perform rapid amplification of cDNA ends to obtain two cysteine-rich clones, PGM-2X and PGM-Z13. PGM-2X has 1071 base pairs (bp) encoding 357 amino acids containing five serine-threonine-rich 16 amino acid tandem repeats, downstream from a cysteine-rich region similar to human and mouse MUC5AC. PGM-Z13 encodes the complete 3'-terminus of PGM and is composed of 3336 bp with a 2964 bp open reading frame encoding 988 amino acids with four serine-threonine-rich tandem repeats upstream from a cysteine-rich region similar to the carboxyl terminal regions of human and rat MUC5AC and human MUC5B. This region is homologous to von Willebrand factor C and D domains involved in acid induced polymerization, and to the carboxyl terminal cystine-knot domain of various mucins, TGF-beta, vWF and norrin, which is involved in dimerization. These newly sequenced cysteine-rich regions of pig gastric mucin may be critical for its gelation and for its observed increased viscosity induced by low pH.

von Willebrand factor and its disorders: an overview of recent molecular studies.

Tuddenham EG
Blood Rev. 1989; 3: 251-62

von Willebrand factor (vWF) is a plasma protein with multiple functions in haemostasis. The vWF gene, located on chromosome 12p2.1, encodes a primary gene product of 2813 amino acids. Post-translational modification, assembly and secretion of vWF are highly complex. The pro vWF promoter is covalently linked by intermolecular disulphide bonds to form a dimer of MW approximately 440 kDa. This then polymerises to form multimers ranging in MW from 1-20 x 10(6). Simultaneously the pro piece of vWF is cleaved, releasing a 741 amino acid peptide known as vW Ag II from the polymerised protomers. Two distinct secretion pathways are found in the endothelial cell, a regulated pathway with storage in Weibl-Palade bodies and a constitutive pathway. Platelets store vWF in their alpha-granules. Mature vWF participates in platelet adhesion, spreading and aggregation and is a carrier of factor VIII, protecting the latter from degradation. Disorders of vWF are highly diverse. At least 20 subtypes of von Willebrand's disease have been described to date, based on features of the vWF present in or absent from patients plasma and platelets. Some patients have reduced amounts of apparently normal vWF whilst others have clearly abnormal vWF with aberrant structure and function. Rare patients virtually or completely lack vWF. The genetic and structural basis of some of these abnormalities is just beginning to emerge. This article outlines the molecular biology and physiology of vWF, and reviews some recent progress on the molecular pathology and genetics of von Willebrand's disease.

Evolution of von Willebrand factor A (VWA) domains.

Tuckwell D
Biochem Soc Trans. 1999; 27: 835-40

The carboxyl-terminal sequence of the human secretory mucin, MUC6. Analysis Of the primary amino acid sequence.

Toribara NW, Ho SB, Gum E, Gum JR Jr, Lau P, Kim YS
J Biol Chem. 1997; 272: 16398-403

The distribution of MUC6 suggests that its primary function is protection of vulnerable epithelial surfaces from damaging effects of constant exposure to a wide range of endogenous caustic or proteolytic agents. A combination of genomic, cDNA. and 3' rapid amplification of cDNA ends techniques was used to isolate the carboxyl-terminal end of MUC6. The 3' nontandem repeat region contained 1083 base pairs of coding sequence (361 amino acids) followed by 632 base pairs of 3'-untranslated region. The coding sequence consists of two distinct regions; region 1 contained the initial 270 amino acids (62% Ser-Thr-Pro with no Cys residues), and region 2 contained the COOH-terminal 91 amino acids (22% Ser-Thr-Pro with 12% Cys). Although region 1 had no homology to any sequences in GenBank, region 2 had approximately 25% amino acid homology to the COOH-terminal regions of human mucins MUC2, -5, and -5B and von Willebrand factor. The shortness of region 2 would leave little of the peptide backbone exposed to a potentially hostile environment. Antibody studies suggest that MUC6 in its native form exists as a disulfide-bonded multimer. The conservation of the 11 cysteine positions in region 2 suggests the importance of this short region to mucin polymerization.

pS2/TFF1 interacts directly with the VWFC cysteine-rich domains of mucins.

Tomasetto C, Masson R, Linares JL, Wendling C, Lefebvre O, Chenard MP, Rio MC
Gastroenterology. 2000; 118: 70-80

BACKGROUND & AIMS: Trefoil factors (TFFs) are secreted gastrointestinal proteins that have been shown to protect and promote healing of the gastrointestinal tract. Moreover, pS2/TFF1 is essential for normal differentiation of the gastric mucosa because deficient mice develop antropyloric adenomas. To date, it is unclear how TFFs mediate their functions. METHODS: Using the yeast 2-hybrid system, we attempted to identify murine TFF1 interacting proteins by screening a stomach and duodenum complementary DNA (cDNA) expression library. RESULTS: Four positive clones were isolated. Sequence and expression studies showed that they corresponded to the murine counterpart of human cDNA sequences encoding carboxy-terminal fragments of mMuc2 (489 residues) and mMuc5AC (427, 430, and 894 residues) mucin proteins. Mutagenesis experiments showed that TFF1 interacts with the 2 mucins through binding with their VWFC1 and VWFC2 (von Willebrand factor C) cysteine-rich domains. CONCLUSIONS: These results show that the gastrointestinal protective effect of TFF1, and presumably of the other TFFs, is caused at least partially by their participation, via mucin binding, in the correct organization of the mucous layer that protects the apical side of the mucosa from deleterious luminal agents.

Amino acid sequence of human von Willebrand factor.

Titani K, Kumar S, Takio K, Ericsson LH, Wade RD, Ashida K, Walsh KA, Chopek MW, Sadler JE, Fujikawa K
Biochemistry. 1986; 25: 3171-84

The complete amino acid sequence of human von Willebrand factor (vWF) is presented. Most of the sequence was determined by analysis of the S-carboxymethylated protein. Some overlaps not provided by the protein sequence analysis were obtained from the sequence predicted by the nucleotide sequence of a cDNA clone [Sadler, J.E., Shelton-Inloes, B.B., Sorace, J., Harlan, M., Titani, K., & Davie, E.W. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 6391-6398]. The protein is composed of 2050 amino acid residues containing 12 Asn-linked and 10 Thr/Ser-linked oligosaccharide chains. One of the carbohydrate chains is linked to an Asn residue in the sequence Asn-Ser-Cys rather than the usual Asn-X-Ser/Thr sequence. The sequence of von Willebrand factor includes several regions bearing evidence of internal gene duplication of ancestral sequences. The protein also contains the tetrapeptide sequence Arg-Gly-Asp-Ser (at residues 1744-1747), which may be a cell attachment site, as in fibronectin. The amino- and carboxyl-terminal regions of the molecule contain clusters of half-cystinyl residues. The sequence is unique except for some homology to human complement factor B.

Concentration of mRNA for von Willebrand factor in platelets of type I von Willebrand disease.

Takenaka T, Kuribayashi K, Tsukiyama M, Nakamine H, Fukuhara Y, Kuno T
Clin Chim Acta. 1996; 245: 125-7

von Willebrand factor (vWF)--why are the largest multimers most efficient in hemostasis?

Stormorken H
Thromb Haemost. 1990; 64: 335-335

A polymorphic (AGGAAT)n tandem repeat in an intron of the canine von Willebrand factor gene.

Shibuya H, Collins BK, Huang TH, Johnson GS
Anim Genet. 1994; 25: 122-122

Evolution of human von Willebrand factor: cDNA sequence polymorphisms, repeated domains, and relationship to von Willebrand antigen II.

Shelton-Inloes BB, Broze GJ Jr, Miletich JP, Sadler JE
Biochem Biophys Res Commun. 1987; 144: 657-65

Four cDNAs extending into the 5'-noncoding region of the human von Willebrand factor cDNA have been characterized. Thirty-four residues of amino-terminal protein sequence for von Willebrand antigen II matched that predicted from the cDNA sequence, confirming that the propeptide of von Willebrand factor is von Willebrand antigen II. Among the known cDNA sequences there are four confirmed single nucleotide differences, of which two may be in linkage disequilibrium, and two would alter the protein sequence. Based on comparisons among the four repeated D domains, an evolutional model has been proposed to account for the distribution of these sequence elements in prepro-von Willebrand factor.

Defective dimerization of von Willebrand factor subunits due to a Cys-> Arg mutation in type IID von Willebrand disease.

Schneppenheim R, Brassard J, Krey S, Budde U, Kunicki TJ, Holmberg L, Ware J, Ruggeri ZM
Proc Natl Acad Sci U S A. 1996; 93: 3581-6

The same heterozygous T -> C transition at nt 8567 of the von Willebrand factor (vWF) transcript was found in two unrelated patients with type III) von Willebrand disease, with no other apparent abnormality. In one family, both alleles were normal in the parents and one sister; thus, the mutation originated de novo in the proposita. The second patient also had asymptomatic parents who, however, were not available for study. The structural consequences of the identified mutation, resulting in the CyS2010 -> Arg substitution, were evaluated by expression of the vWF carboxyl-terminal domain containing residues 1366-2050. Insect cells infected with recombinant baculovirus expressing normal vWF sequence secreted a disulfide linked dimeric molecule with an apparent molecular mass of 150 kDa before reduction, yielding a single band of 80 kDa after disulfide bond reduction. In contrast, cells expressing the mutant fragment secreted a monomeric molecule of apparent molecular mass of 80 kDa, which remained unchanged after reduction. We conclude that CyS2010 is essential for normal dimerization of vWF subunits through disulfide bonding of carboxyl-terminal domains and that a heterozygous mutation in the corresponding codon is responsible for defective multimer formation in type III) von Willebrand disease.

A Bethlem myopathy Gly to Glu mutation in the von Willebrand factor A domain N2 of the collagen alpha3(VI) chain interferes with protein folding.

Sasaki T, Hohenester E, Zhang RZ, Gotta S, Speer MC, Tandan R, Timpl R, Chu ML
FASEB J. 2000; 14: 761-8

A single G1679E mutation in the amino-terminal globular domain N2 of the alpha3 chain of type VI collagen was found in a large family affected with Bethlem myopathy. Recombinant production of N2 ( approximately 200 residues) in transfected mammalian cells has now been used to examine the possibility that the mutation interfered with protein folding. The wild-type form and a G1679A mutant were produced at high levels and shown to fold into a stable globular structure. Only a small amount of secretion was observed for mutants G1679E and G1679Q, which apparently were efficiently degraded within the cells. Homology modeling onto the related von Willebrand factor A1 structure indicated that substitution of G1679 by the bulky E or Q cannot be accommodated without considerable changes in the folding pattern. This suggests protein misfolding as a molecular basis for this particular mutation in Bethlem myopathy, in agreement with radioimmunoassay data showing reduced levels of domain N2 in cultured fibroblasts from two patients.

Cloning and characterization of two cDNAs coding for human von Willebrand factor.

Sadler JE, Shelton-Inloes BB, Sorace JM, Harlan JM, Titani K, Davie EW
Proc Natl Acad Sci U S A. 1985; 82: 6394-8

A cDNA library was prepared in lambda gt11 bacteriophage from poly(A)+ RNA isolated from primary cultures of endothelial cells from human umbilical vein. Approximately 2.5 million independent recombinants were screened and 2 of those were found to synthesize a fusion protein with beta-galactosidase that reacted with rabbit antibody against human von Willebrand factor. Comparison of the amino acid sequence translated from the cDNA insert of the two clones with the amino acid sequence determined by Edman degradation of the protein established that both phage isolates code for von Willebrand factor. The first clone (lambda HvWF1) contained an insert of 404 nucleotides that corresponded to amino acid residues 1-110 in the mature protein circulating in blood, in addition to a portion (24 amino acids) of a prepro leader sequence. The second cDNA clone (lambda HvWF3) contained an insert of 4.9 kilobases that coded for the carboxyl-terminal 1525 amino acids of von Willebrand factor, a stop codon of TGA, 134 nucleotides of 3' noncoding sequence, and a poly(A) tail of 150 nucleotides. The two clones together code for greater than 80% of the molecule circulating in blood. The same carboxyl-terminal lysine residue was identified in the mature protein as well as in the cDNA, indicating that all of the proteolytic processing that occurs during the biosynthesis and assembly of von Willebrand factor is associated with the amino-terminal portion of the precursor protein. The amino acid sequence of von Willebrand factor indicates the presence of two different internal gene duplications and one triplication. These repetitive amino acid sequences account for about one-half of the amino acids present in the mature protein. The tetrapeptide sequence of Arg-Gly-Asp-Ser, which mediates the cell attachment and platelet binding activity of fibronectin, was also identified in the carboxyl-terminal portion of von Willebrand factor.

Commentary: a new classification for von Willebrand disease.

Sadler JE, Gralnick HR
Blood. 1994; 84: 676-9

A database of polymorphisms in the von Willebrand factor gene and pseudogene. For the Consortium on von Willebrand Factor Mutations and Polymorphisms and the Subcommittee on von Willebrand Factor of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis.

Sadler JE, Ginsburg D
Thromb Haemost. 1993; 69: 185-91

Nucleotide sequence polymorphisms in the von Willebrand factor (vWF) gene are useful for genetic studies in von Willebrand disease (vWD). This database describes 33 known vWF polymorphisms distributed throughout the vWF gene. DNA sequence information is available for 21 of these sites. The most informative system is a tetranucleotide repeat polymorphism in vWF intron 40. Sixteen of these polymorphisms are within vWF exons, and approximately half of them also alter the encoded amino acid sequence. Many occur close to mutations that cause vWD. The high prevalence of vWF polymorphisms must be considered in the analysis of candidate vWD mutations. In addition to the vWF gene on chromosome 12, there is a partial unprocessed vWF pseudogene on chromosome 22 that corresponds to vWF exons 23 to 34. Three polymorphisms have been assigned to the vWF pseudogene. Because the vWF gene and pseudogene have diverged only approximately 3.1% in DNA sequence, correct assignment of polymorphisms to either locus can be difficult in the region of homology. This problem has been solved in some cases by comparison of the published sequences and predicted restriction maps for the gene and pseudogene.

Structure and function of von Willebrand factor.

Ruggeri ZM
Thromb Haemost. 1999; 82: 576-84

Acquired abnormalities of von Willebrand factor: facts to consider in patients with unexpected bleeding.

Ruggeri ZM
J Lab Clin Med. 1993; 121: 377-9

von Willebrand factor.

Ruggeri ZM
J Clin Invest. 1997; 100: 416-416

Identification of a His54Gln substitution in von Willebrand factor from a patient with defective binding of factor VIII.

Rick ME, Krizek DM
Am J Hematol. 1996; 51: 302-6

A patient with type 2N ("Normandy" variant) von Willebrand's disease is described. Her von Willebrand factor level was borderline low, while her factor VIII was markedly decreased to 7%. Her plasma von Willebrand factor demonstrated a decreased ability to complex with factor VIII in vitro, binding less than 10% when compared to normal plasma von Willebrand factor. The factor VIII released into the circulation after the patient received DDAVP had a shortened survival in vivo. Nucleotide sequence analysis revealed a T-to-A transition at nucleotide 2451 on both alleles. This transition results in a substitution of Gln for His at amino acid 54 in the mature subunit of von Willebrand factor.

Discrepancy between IIA phenotype and IIB genotype in a patient with a variant of von Willebrand disease.

Ribba AS, Christophe O, Derlon A, Cherel G, Siguret V, Lavergne JM, Girma JP, Meyer D, Pietu G
Blood. 1994; 83: 833-41

Type IIA and IIB von Willebrand disease (vWD) result from qualitative abnormalities of von Willebrand factor (vWF) characterized by an absence in plasma of high molecular weight vWF multimers and an abnormal reactivity of vWF towards platelet glycoprotein (GP) Ib, which is decreased in type IIA and increased in type IIB. In this report, we describe the case of a patient having a IIA vWD phenotype associated with an intermittent thrombocytopenia atypical in this subtype but observed in type IIB vWD. The patient plasma vWF showed an absence of high molecular weight and intermediate multimers and had a decreased binding capacity to GPIb. The affinity of botrocetin was normal for plasma vWF from the propositus. Analysis of the propositus vWF gene showed the presence of a substitution Val 551 to Phe of the mature vWF subunit. This mutation is localized within a 509-695 disulphide loop of the vWF that plays an important role in the binding to GPIb and is where most of the molecular defects described so far were associated with type-IIB vWD. We have reproduced the Val 551 Phe substitution onto the vWF cDNA, expressed it in COS-7 cells, and performed structural and functional analysis of the mutant recombinant protein (rvWFPhe 551). The rvWFPhe 551 had a normal multimeric structure and showed the capacity to spontaneously interact with GPIb. Botrocetin had a decreased affinity for rvWFPhe 551. In conclusion, the Val 551 Phe mutation modifies the affinity of vWF for platelet GPIb, as does a type IIB mutation, and may be responsible for the thrombocytopenia of the patient and the clearance of the high molecular weight and intermediate-sized multimers of vWF from the plasma. The study of the rvWFPhe 551 has confirmed the discrepancy between the IIA phenotype and the IIB genotype of the patient.

The genetic defect of type I von Willebrand disease "Vicenza" is linked to the von Willebrand factor gene.

Randi AM, Sacchi E, Castaman GC, Rodeghiero F, Mannucci PM
Thromb Haemost. 1993; 69: 173-6

Type I von Willebrand disease (vWD) Vicenza is a rare variant with autosomal dominant transmission, characterized by the presence of supranormal von Willebrand factor (vWF) multimers in plasma, similar to those normally found in endothelial cells and megakaryocytes. The patients have very low levels of plasma vWF contrasting with a mild bleeding tendency. The pathophysiology of this subtype is still unknown. The presence of supranormal multimers in the patients' plasma could be due to a mutation in the vWF molecule which affects post-translational processing, or to a defect in the cells' processing machinery, independent of the vWF molecule. In order to determine if type I vWD Vicenza is linked to the vWF gene, we studied six polymorphic systems identified within the vWF gene in two apparently unrelated families with type I vWD Vicenza. The results of this study indicate a linkage between vWF gene and the type I vWD Vicenza trait. This strongly suggests that type I vWD Vicenza is due to a mutation in one of the vWF alleles, which results in an abnormal vWF molecule that is processed to a lesser extent than normal vWF.

[Mechanisms of functional change of von Willebrand factor]

Ramos F, Batlle J, Lopez Borrasca A
Med Clin (Barc). 1989; 92: 588-94

Sex-related difference in plasma von Willebrand factor (vWF:Ag and vWF:RiCof) levels in adolescents.

Quiroga T, Tagle R, Pereira J, Mezzano D
Thromb Haemost. 1994; 71: 800-1

Amino acid sequence of the murine Mac-1 alpha chain reveals homology with the integrin family and an additional domain related to von Willebrand factor.

Pytela R
EMBO J. 1988; 7: 1371-8

Clones encoding the Mac-1 alpha chain were selected from a mouse macrophage cDNA library by screening with oligonucleotide probes based on the sequence of a genomic clone encoding the N-terminus of the mature protein. The sequence of overlapping clones (4282 nt) was determined and translated into a protein of 1137 amino acids and a signal peptide of 15 amino acids. The Mac-1 sequence was found to be related to the alpha chain sequences of three other members of the integrin family of cell adhesion receptors, i.e. the fibroblast receptors for fibronectin and vitronectin and the platelet glycoprotein IIb/IIIa. All four sequences share a number of structural features, like the position of 13 cysteine residues, a transmembrane domain near the C-terminus and the location of three putative binding sites for divalent cations. Furthermore, a conserved sequence motif is repeated seven times in the N-terminal half of the molecule and three of these repeats include putative Ca/Mg-binding sites of the general structure DXDXDGXXD. On the other hand, Mac-1 contains a unique domain of 220 amino acids inserted into the N-terminal part of the integrin structure. This additional domain is homologous to a repeated domain found in von Willebrand factor, cartilage matrix protein and in the complement factors B and C2. In two of these proteins, the homologous domain is likely to be involved in binding to collagen fibrils. Therefore, Mac-1 may also bind to collagen, which could play a role in the interaction of leukocytes with the subendothelial matrix.

A rapid and sensitive method for the analysis of von Willebrand factor multimeric structure.

Perutelli P, Boeri E, Mori PG
Haematologica. 1997; 82: 510-510

Structural and functional modelling of von Willebrand factor type A domains in complement and coagulation.

Perkins SJ, Hinshelwood J, Edwards YJ, Jenkins PV
Biochem Soc Trans. 1999; 27: 815-20

A de novo mutation in exon 28 of the von Willebrand factor gene in a patient with type IIA von Willebrand's disease coincides with an MboI polymorphism in the von Willebrand factor pseudogene.

Perez-Casal M, Daly M, Peake I
Hum Mol Genet. 1993; 2: 2159-61

Molecular cloning, expression and assembly of multimeric von Willebrand factor.

Pannekoek H, Voorberg J
Baillieres Clin Haematol. 1989; 2: 879-96

Recently, substantial progress has been made in our knowledge of the domains involved in correlating structure and function of vWF, as well as in the biosynthesis and assembly of multimeric vWF. These studies were greatly supported by the development of three new techniques. (1) In vitro culturing of (human) vascular endothelial cells has allowed studies on the subcellular localization for dimerization of pro-vWF subunits, multimerization, carbohydrate and proteolytic processing. Moreover, this approach has provided insight into the complex intracellular routing of vWF that proceeds by either one of two pathways. During the constitutive pathway, vWF is packaged in secretory vesicles that are rapidly secreted both at the luminal and at the basolateral side. The regulated pathway includes storage of vWF molecules in specialized organelles, i.e. the Weibel-Palade bodies. (2) The application of proteases to dissect purified multimeric vWF and to assign function(s) to defined proteolytic fragments of vWF. Monoclonal antibodies, raised against native vWF, that block specific functions and bind to fragments are subsequently employed to correlate structure and function. More precise localizations of functions are now feasible, using overlapping synthetic peptides derived from the primary amino acid sequence of (pro)-vWF and antibodies raised against such peptides. This approach has permitted a fine mapping of the interaction site of vWF with the platelet receptor glycoprotein (GP) IIB/IIIA. (3) Molecular cloning of full-length vWF cDNA and the development of eukaryotic expression systems have substantially increased the possibilities to investigate structures on pro-vWF involved in the biosynthesis and the assembly of multimers. In particular, the construction of point and deletion mutants of vWF, employing vWF cDNA, and subsequent expression in heterologous cells have demonstrated that proteolytic processing of pro-vWF, between arginine (Arg-763) and serine (Ser-764), to generate free propolypeptide and mature vWF is not required for multimerization. Finally, the propolypeptide has an obligatory role for the formation of multimers, enabling interdimer disulphide bonding of free sulphhydryl groups located within the mature vWF part of pro-vWF.

About the von Willebrand factor.

Ozsoylu S
Pediatr Hematol Oncol. 1998; 15: 467469-467469

A polymorphism of the human von Willebrand factor (vWf) gene with BamHI.

Nishino K, Lynch DC
Nucleic Acids Res. 1986; 14: 4697-4697

von Willebrand disease in the RIIIS/J mouse is caused by a defect outside of the von Willebrand factor gene.

Nichols WC, Cooney KA, Mohlke KL, Ballew JD, Yang A, Bruck ME, Reddington M, Novak EK, Swank RT, Ginsburg D
Blood. 1995; 86: 2461-2461

von Willebrand disease and quantitative variation in von Willebrand factor.

Mohlke KL, Ginsburg D
J Lab Clin Med. 1997; 130: 252-61

Insolubilized von Willebrand factor and the initial events in hemostasis.

Moake JL
J Lab Clin Med. 1989; 114: 1-3

von Willebrand factor: structure and function.

Meyer D, Girma JP
Thromb Haemost. 1993; 70: 99-104

von Willebrand factor: a target for inhibition of thrombosis.

Meyer D
Nouv Rev Fr Hematol. 1993; 35: 255-7

A G+3-to-T donor splice site mutation leads to skipping of exon 50 in von Willebrand factor mRNA.

Mertes G, Ludwig M, Finkelnburg B, Krawczak M, Schwaab R, Brackmann HH, Olek K
Genomics. 1994; 24: 190-1

Canine von Willebrand factor expresses a multimeric composition similar to human von Willebrand factor.

McCarroll DR, Lothrop SA, Dolan MC, McDonald TP
Exp Hematol. 1987; 15: 1060-7

Canine von Willebrand factor (vWf) was compared to human vWf. Antisera raised against human vWf or canine vWf cross-reacted with both heterologous proteins and reactions of partial identity were seen using crossed immunoelectrophoresis. Similar patterns of multimerization were obtained for vWf from both canine and human sources using the enzyme-linked immunoelectrotransfer blot method. However, the canine protein displayed an altered electrophoretic mobility. The molecular weight of the vWf monomer was estimated by SDS-PAGE and found to be indistinguishable from that of human vWf monomer. Canine vWf is decreased in animals with clinically evident hypothyroidism and in heterozygous "carriers" of von Willebrand's disease (vWd) that display no clinical symptoms of vWd. Results expand the concept that von Willebrand's disease in dogs may be a useful model for study of vWd in humans, and that immunochemical methods established for studies of human vWf appear appropriate for studies of canine vWf.

Antibodies to von Willebrand factor in von Willebrand disease.

Mannucci PM, Federici AB
Adv Exp Med Biol. 1995; 386: 87-92

Structure of the gene for human von Willebrand factor.

Mancuso DJ, Tuley EA, Westfield LA, Worrall NK, Shelton-Inloes BB, Sorace JM, Alevy YG, Sadler JE
J Biol Chem. 1989; 264: 19514-27

von Willebrand factor is a large multimeric plasma protein composed of identical subunits which contain four types of repeated domains. von Willebrand factor is essential for normal hemostasis, and deficiency of von Willebrand factor is the most common inherited bleeding disorder of man. Four human genomic DNA cosmid libraries and one bacteriophage lambda library were screened with von Willebrand factor cDNA probes. Twenty positive overlapping clones were characterized that span the entire von Willebrand factor gene. A high-resolution restriction map was constructed for approximately 75% of the locus and a total of approximately 33.8 kilobases was sequenced on both strands including all intron-exon boundaries. The gene is approximately 178 kilobases in length and contains 52 exons. The exons vary from 40 to 1379 base pairs in length, and the introns vary from 97 base pairs to approximately 19.9 kilobases in length. The signal peptide and propeptide (von Willebrand antigen II) of von Willebrand factor are encoded by 17 exons in approximately 80 kilobases of DNA while the mature subunit of von Willebrand factor and 3' noncoding region are encoded by 35 exons in the remaining approximately 100 kilobases of the gene. A number of repetitive sequences were identified including 14 Alu repeats and a approximately 670-base pair TCTA simple repeat in intron 40 that is polymorphic. Regions of the gene that encode homologous domains have similar structures, supporting a model for their origin by gene segment duplication.

Characterization of partial gene deletions in type III von Willebrand disease with alloantibody inhibitors.

Mancuso DJ, Tuley EA, Castillo R, de Bosch N, Mannucci PM, Sadler JE
Thromb Haemost. 1994; 72: 180-5

von Willebrand factor gene deletions were characterized in four patients with severe type III von Wilebrand disease and alloantibodies to von Willebrand factor. A PCR-based strategy was used to characterize the boundaries of the deletions. Identical 30 kb von Willebrand factor gene deletions which include exons 33 through 38 were identified in two siblings of one family by this method. A small 5 base pair insertion (CCTGG) was sequenced at the deletion breakpoint. PCR analysis was used to detect the deletion in three generations of the family, including two family members who are heterozygous for the deletion. In a second family, two type III vWD patients, who are distant cousins, share an approximately 56 kb deletion of exons 22 through 43. The identification and characterization of large vWF gene deletions in these type III vWD patients provides further support for the association between large deletions in both von Willebrand factor alleles and the development of inhibitory alloantibodies.

Type 2M:Milwaukee-1 von Willebrand disease: an in-frame deletion in the Cys509-Cys695 loop of the von Willebrand factor A1 domain causes deficient binding of von Willebrand factor to platelets.

Mancuso DJ, Kroner PA, Christopherson PA, Vokac EA, Gill JC, Montgomery RR
Blood. 1996; 88: 2559-68

This report examines the genetic basis of a variant form of moderately severe von Willebrand disease (vWD) characterized by low plasma von Willebrand factor antigen (vWF:Ag) levels and normal multimerization, typical of type 1 vWD, but disproportionately-low agonist-mediated platelet-binding activity. We identified an in-frame deletion in vWF exon 28 in three generations of affected family members, who are heterozygous for this mutation. The deletion of nucleotides 4,173-4,205 results in the loss of amino acids Arg629-Gln639 in the Cys509-Cys695 loop of the A1 domain in mature vWF. The secreted mutant vWF showed a normal multimeric profile but did not bind to platelets in the presence of optimal concentrations of either ristocetin or botrocetin. The mutant vWF also failed to interact with heparin, and with vWF monoclonal antibody AvW3, which blocks the binding of vWF to GPlb. In addition, mutant vWF showed reduced secretion from transfected cells concomitant with increased intracellular levels. These results confirm that the deletion is the genetic defect responsible for the reduced interaction of vWF with platelets. We have designated this new variant type 2M:Milwaukee-1 vWD. Our analysis suggests that the potential frequency of this phenotype in individuals diagnosed with type 1 vWD is about 0.5%.

von Willebrand factor, now cloned.

Lynch DC, Zimmerman TS, Ruggeri ZM
Br J Haematol. 1986; 64: 15-20

Subunit composition of oligomeric human von Willebrand factor.

Lynch DC, Zimmerman TS, Kirby EP, Livingston DM
J Biol Chem. 1983; 258: 12757-60

The oligomerization of human endothelial cell-synthesized von Willebrand factor (vWf) has been studied by gel chromatography in columns of Sephacryl S-500 and by discontinuous agarose gel electrophoresis. A quantitative recovery of high Mr vWf oligomers has been obtained after binding to a monoclonal anti-vWf-Sepharose adduct. This reagent has been used to analyze gel filtration chromatographic elution profiles of [35S]methionine-labeled culture medium and cell lysate. It was determined that high Mr oligomers are present in endothelial cell lysates as well as in the medium overlying these cells and are composed of Mr 225,000 subunits. When vWf oligomers were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence of a reducing agent, the Mr 240,000 subunit (provWf) was not observed to oligomerize beyond the dimer stage to a significant degree. Therefore, vWf oligomerization appears to be facilitated by conversion of provWf subunits to mature vWf subunits, most likely by proteolytic removal of sequences unique to the intracellular precursor.

Molecular cloning of cDNA for human von Willebrand factor: authentication by a new method.

Lynch DC, Zimmerman TS, Collins CJ, Brown M, Morin MJ, Ling EH, Livingston DM
Cell. 1985; 41: 49-56

We have identified a 2.4 kb partial cDNA clone (pDL34) for human von Willebrand factor (vWf) mRNA. pDL34 was selected by screening an endothelial cell cDNA library with a radiolabeled reverse transcript of mRNA obtained by specific immunoisolation of vWf polysomes from endothelial cells. pDL34 selectively hybridized to an endothelial cell-associated 9.5 kb mRNA. To confirm its identity, SP6 RNA polymerase was used to generate in vitro transcripts of the cDNA. This synthetic RNA, truncated at its 5' end, directed the synthesis of several unique polypeptides in rabbit reticulocyte lysates. These polypeptides were immunoprecipitated by polyclonal and monoclonal anti-vWf antibodies. These results indicate that pDL34 contains an authentic partial copy of vWf mRNA. In vitro transcription of partial cDNA clones and translation of the resulting RNAs may be a useful general method of verifying the identity of various cDNA clones in circumstances where antibodies are available and protein sequence is not.

Nonisotopic semiquantitation of low molecular weight von Willebrand factor species: its use in pulmonary hypertension.

Lopes AA, Maeda NY
Acta Haematol. 1993; 89: 216-8

Primary structure of the factor VIII binding domain of human, porcine and rabbit von Willebrand factor.

Lavergne JM, Piao YC, Ferreira V, Kerbiriou-Nabias D, Bahnak BR, Meyer D
Biochem Biophys Res Commun. 1993; 194: 1019-24

von Willebrand factor (vWF) binds to Factor VIII (FVIII) and the FVIII binding domain has been localized to the amino-terminal of the vWF subunit. The DNA sequence coding for part of the vWF precursor (provWF) including the FVIII binding domain has been compared in man, pig and rabbit. The sequenced fragment corresponds to nucleotides 2416 to 2886 of the human vWF cDNA and encodes for the last 41 amino acids of the propolypeptide, the cleavage site and the first 116 amino acids of the mature vWF subunit. The homology of the three deduced amino acids sequences is remarkable: 88% between porcine and human and 87% between rabbit and human sequences. Four contiguous amino acids are lacking in the rabbit propolypeptide (-10 to -7) when compared to the human and porcine sequences. The cleavage site of the propolypeptide is conserved in the three species as well as amino acids where mutations in the human gene lead to a binding defect of vWF to FVIII. The Asn-94 N-glycosylation site is present in the human and rabbit sequences but absent in the pig sequence.

Identification of a new cell adhesion motif in two homologous peptides from the COOH-terminal cell binding domain of human thrombospondin.

Kosfeld MD, Frazier WA
J Biol Chem. 1993; 268: 8808-14

Thrombospondin-1 (TS1) contains at least four domains that support cell attachment. The COOH-terminal cell binding domain (CBD) was first identified with a monoclonal antibody against TS1 that blocked secretion-dependent platelet aggregation. Subsequently, this domain of TS1 has been found to bind a number of normal and transformed cells. We have localized attachment sites for human melanoma cells (G361) within the CBD to two noncontiguous 30-residue peptides designated C4 and C7 (Kosfeld, M. D., and Frazier, W. A. (1991) J. Biol. Chem. 267, 16230-16236). Here we report studies to define the active sequences within C4 and C7. An octapeptide, RFYVVMWK (4N1-1), from C4 and a pentapeptide, IRVVM (7N3-1), from C7 were found to support attachment of G361 melanomas, K562 erythroleukemia cells, HT1080 fibrosarcomas, C32 amelanotic melanomas, and endothelial cells. These peptides also inhibit the adhesion of cells to the recombinant CBD of TS1. The hexapeptide RFYVVM (4N1-2) also inhibits cell attachment. The inhibitory effect of combinations of C4- and C7-derived peptides is synergistic. The sequences 4N1-1 and 7N3-1 of TS1 share homology with two cell adhesive peptides from laminin (LM), LMF9 and LMPA22-2, respectively. These TS1 and LM peptides are interchangeable in inhibiting the adhesion of G361 cells to LM or TS1, suggesting a possible sharing of receptors by LM and TS1. K562 cells, however, bound only to TS1, and this binding was inhibited preferentially by the TS1 CBD peptides, indicating a receptor specific for TS1 which does not recognize LM. The active TS1 peptides are highly conserved among five species and four isoforms of TS1. Homologs of the TS1 peptides are found in tenascin, a matrix protein that shares several properties with TS1 and in factor VIII, alpha 2-macroglobulin, and von Willebrand factor.

The globular domains of type VI collagen are related to the collagen-binding domains of cartilage matrix protein and von Willebrand factor.

Koller E, Winterhalter KH, Trueb B
EMBO J. 1989; 8: 1073-7

Type VI collagen is a transformation-sensitive glycoprotein of the extracellular matrix of fibroblasts. We have isolated and sequenced several overlapping cDNA clones (4153 bp) which encode the entire alpha 2 subunit of chicken type VI collagen. The deduced amino acid sequence predicts that the alpha 2(VI) polypeptide consists of 1015 amino acid residues that are arranged in four domains: a hydrophobic signal peptide of 20 residues, an amino-terminal globular domain of 228 residues, a collagenous segment of 335 residues and a carboxy-terminal globular domain of 432 residues. The collagenous domain contains seven Arg-Gly-Asp tripeptide units, some of which are likely to be used as cell-binding sites. The globular domains contain three homologous repeats with an average length of 180 amino acid residues. These repeats show a striking similarity to the collagen-binding motifs found in von Willebrand factor and cartilage matrix protein. We therefore speculate that the globular domains of the alpha 2(VI) polypeptide may interact with collagenous structures.

Structure of the gene for cartilage matrix protein, a modular protein of the extracellular matrix. Exon/intron organization, unusual splice sites, and relation to alpha chains of beta 2 integrins, von Willebrand factor, complement factors B and C2, and epidermal growth factor.

Kiss I, Deak F, Holloway RG Jr, Delius H, Mebust KA, Frimberger E, Argraves WS, Tsonis PA, Winterbottom N, Goetinck PF
J Biol Chem. 1989; 264: 8126-34

The entire gene for chicken cartilage matrix protein (CMP) has been isolated and characterized by restriction mapping, electron microscopy, nuclease S1 mapping, and sequence analysis. The gene, which is present in a single copy in the chicken genome, is 18 kilobase pairs long and comprises eight exons and seven introns. It has two transcription initiation sites, 8 base pairs from each other. A sequence very homologous to the consensus nuclear factor III binding-site sequence, a CAT- and a TATA-like sequence are found in the promoter region and ATTAAA is used as a polyadenylation signal. The nucleotide sequence defines a primary translation product of 493 amino acids which consists of a 23-amino acid signal peptide and two large repeated domains connected by an epidermal growth factor module. Amino acid sequences homologous to those of the repeated domains are present in the type A repeats of von Willebrand factor, complement factors B and C2, and in the alpha chains of the integrins Mac-1, p150,95, and LFA-1. The exon-intron structure indicates that the CMP gene may have arisen by exon duplication and exon shuffling during evolution. The GT-AG splice rule cannot be applied for the excision of the last intron of the CMP pre-mRNA. The donor splice site of intron G is basically different from the consensus sequence indicating that a novel type of splicing mechanism might exist in cartilage.

Regulation of factor VIII expression and activity by von Willebrand factor.

Kaufman RJ, Pipe SW
Thromb Haemost. 1999; 82: 201-8

Requirement for both D domains of the propolypeptide in von Willebrand factor multimerization and storage.

Journet AM, Saffaripour S, Wagner DD
Thromb Haemost. 1993; 70: 1053-7

Biosynthesis of the adhesive glycoprotein von Willebrand factor (vWf) by endothelial cells results in constitutive secretion of small multimers and storage of the largest multimers in rod-shaped granules called Weibel-Palade bodies. This pattern is reproduced by expression of pro-vWf in heterologous cells with a regulated pathway of secretion, that store the recombinant protein in similar elongated granules. In these cells, deletion of the vWf prosequence prevents vWf storage. The prosequence, composed of two homologous domains (D1 and D2), actively participates in vWf multimer formation as well. We expressed deletion mutants lacking either the D1 domain (D2vWf) or the D2 domain (D1vWf) in various cell lines to analyze the relative importance of each domain in vWf multimerization and storage. Both proteins were secreted efficiently without being retained in the endoplasmic reticulum. Despite this, neither multimerized past the dimer stage and they were not stored. We conclude that several segments of the prosequence are jointly involved in vWf multimerization and storage.

Similarities of integumentary mucin B.1 from Xenopus laevis and prepro-von Willebrand factor at their amino-terminal regions.

Joba W, Hoffmann W
J Biol Chem. 1997; 272: 1805-10

Frog integumentary mucin B.1 (FIM-B.1) contains various cysteine-rich modules. In the past, a COOH-terminal "cystine knot" motif has been found that is similar to von Willebrand factor; this region is generally known to be responsible for dimerization processes. Furthermore, a "complement control protein" motif is present as an internal cysteine-rich domain in FIM-B.1. We characterize here the missing 75% toward the NH2 terminus of the FIM-B.1 precursor by molecular cloning. Analogous to prepro-von Willebrand factor, four elements with considerable similarity to D-domains are present (i.e. D1-D2-D'-D3). These domains have been described as essential for the multimerization of von Willebrand factor. Thus, the general structure of FIM-B.1 resembles that of the human mucin MUC2 as well as prepro-von Willebrand factor; these three molecules at least seem to share common structural elements allowing similar multimerization mechanisms.

Comparison of the 5'-flanking sequences of the human and bovine von Willebrand factor-encoding genes reveals alternation of highly homologous domains with species-specific Alu-type repeats.

Janel N, Schwachtgen JL, Bakhshi MR, Barek L, Meyer D, Kerbiriou-Nabias D
Gene. 1995; 167: 291-5

von Willebrand factor (vWF), a multimeric glycoprotein important for hemostasis, is specifically synthesized in endothelial cells and in platelet precursors (megakaryocytes). Recent studies from two laboratories, including ours, were published regarding the cell-specific transcription of reporter genes controlled by the human (hu) vWF promoter in transfected bovine (bo) endothelial cells and cells of non-endothelial origins. In order to verify that the regulatory domains previously characterized in the 5' region of hu vWF are also present in bo vWF, we have sequenced 1.9 kb upstream from the cap site, plus five exons. The comparison of human and bovine exons two to five shows homology of 83% at the nucleotide (nt) level and 78% at the deduced amino-acid sequence level. The bovine and human exons one, which are non-coding and span 233 and 250 bp, respectively, are only 64% homologous. In the first exon, potentially involved in endothelial-cell-specific transcription, the binding site for factor Sp1 is present in bo vWF, whereas the GATA sequence is replaced by a GACA sequence. The sequence corresponding to the human basal promoter, located between nt -89 and +19, is well conserved with 82% homology. However, the human TAATTA sequence (at nt -32) considered to be a TATA box, is replaced by TCATTA, and the CCAAT element at nt -18 is replaced by CCTGT. Among domains involved in transcription, the negative regulatory domain located 5' from the core promoter is highly conserved. The bovine sequence upstream from the first intron can be aligned with the human sequence up to nt -656 which is located in a polymorphic poly(GT)18-26 sequence. At this site, the bovine DNA contains an insertion of 523 bp which corresponds to a bovine Alu-type art2 repeat of 331 bp flanked by bovine microsatellites. The art2 sequence is an Alu-type repeat in artiodactyls with at least 100,000 copies in the bovine genome. Upstream from this insertion, 368 bp of the bovine sequence can be aligned with the human counterpart up to a 9-bp element which flanks an human Alu repeat which is absent from the bovine DNA. Upstream of the human Alu insertion and a duplicate of the 9-bp element, the two sequences are again homologous.

Primary structure of the propeptide and factor VIII-binding domain of bovine von Willebrand factor.

Janel N, Ribba AS, Cherel G, Kerbiriou-Nabias D, Meyer D
Biochim Biophys Acta. 1997; 1339: 4-8

A 2811 base-pair cDNA, encoding the amino-terminal part of the bovine pre-pro-von Willebrand factor, was characterized and sequenced. The deduced amino acid sequence shares significant homology with the human von Willebrand antigen II and the amino-terminal part of the factor VIII-binding domain of von Willebrand factor. In contrast to human, there is no RGD motif in the bovine von Willebrand antigen II. High levels of Cys, characteristic of D domains, are also found in bovine and the Cys position is markedly conserved between the two species.

von Willebrand factor shares a distinctive cysteine-rich domain with thrombospondin and procollagen.

Hunt LT, Barker WC
Biochem Biophys Res Commun. 1987; 144: 876-82

The identification of common domains among different proteins is of great interest at present. We have found that a cysteine-rich domain in thrombospondin, also present in types I and III procollagen alpha 1 chains, is related to two internally homologous domains in von Willebrand factor. In the four proteins these domains are similar in length (64-74 residues) and have nine invariant cysteines, some of which form intramolecular disulfide bonds. The structural and functional similarities of this domain in the four kinds of proteins, and its correspondence in procollagen to an exon, support our hypothesis of a common origin for the domain.

Concentration of von Willebrand factor in diabetes. Did authors measure serum or plasma concentrations?

Hunt BJ
BMJ. 1996; 312: 642-642

von Willebrand factor mutation enhancing interaction with platelets in patients with normal multimeric structure.

Holmberg L, Dent JA, Schneppenheim R, Budde U, Ware J, Ruggeri ZM
J Clin Invest. 1993; 91: 2169-77

Variant von Willebrand disease designated as type I New York or type Malmo is characterized by enhanced ristocetin-induced platelet agglutination with normal von Willebrand factor multimeric distribution in plasma. We have studied four such patients belonging to three unrelated families and found in all of them a unique cytosine-to-thymine transition changing the codon for Pro503 (CCG) to Leu (CTG). In three patients the mutant allele also had a silent mutation in the codon for Ser500 (TCG-->TCA). Both nucleotide changes are present in the von Willebrand factor pseudogene; however, the characterization of distinctive markers where the gene and pseudogene differ, as well as the examination of amplified cDNA derived from platelet mRNA, confirmed that the abnormality occurs in the von Willebrand factor gene of the patients. Moreover, recombinant expression of the isolated glycoprotein Ib-binding domain of von Willebrand factor provided direct evidence that the Pro503-->Leu mutation is responsible for enhanced platelet reactivity to lower ristocetin concentrations. These results define a new structural element affecting the affinity of von Willebrand factor for glycoprotein Ib and establish the molecular basis of a variant form of von Willebrand disease.

Biosynthesis and molecular architecture of gel-forming mucins: implications from an amphibian model system.

Hoffmann W, Joba W
Biochem Soc Trans. 1995; 23: 805-10

Identification of two mutations (Arg611Cys and Arg611His) in the A1 loop of von Willebrand factor (vWF) responsible for type 2 von Willebrand disease with decreased platelet-dependent function of vWF.

Hilbert L, Gaucher C, Mazurier C
Blood. 1995; 86: 1010-8

We report the identification of von Willebrand factor (vWF) gene mutations within exon 28 occurring in three unrelated families with an infrequent form of type 2 von Willebrand disease (vWD). A C-->T transition and a G-->A transition, both at the codon for arginine 611 of the mature vWF subunit, were found. They result in either a cysteine or an histidine substitution, respectively. Patients were found to be heterozygous for these substitutions and the vWD was transmitted dominantly. These substitutions have been reproduced by in vitro mutagenesis of full-length cDNA of vWF and transiently expressed in Cos-7 cells. The corresponding recombinant vWFs (rvWF) exhibited decreased expression and a significant decrease in the high molecular weight multimeric forms. In addition, ristocetin- and botrocetin-induced binding of mutated rvWFs to platelets were markedly decreased as compared with that for the wild-type rvWFs. Thus, the structural and functional characterization of both mutated rvWFs confirmed that the two nucleotide substitutions identified at position 611 of the mature subunit of vWF are real mutations. Although they are located in the A1 loop containing most of the type 2B mutations inducing increased affinity of vWF for platelet glycoprotein Ib, they are responsible for abnormal vWF with decreased platelet-dependent function.

Leu 697-->Val mutation in mature von Willebrand factor is responsible for type IIB von Willebrand disease.

Hilbert L, Gaucher C, de Romeuf C, Horellou MH, Vink T, Mazurier C
Blood. 1994; 83: 1542-50

Type IIB von Willebrand disease is characterized by the selective loss of high molecular weight von Willebrand factor (vWF) multimers from plasma and enhanced platelet agglutination of platelet-rich-plasma in the presence of low concentrations of ristocetin. We identified, in two related patients, a C-->G transversion resulting in the substitution of Valine for Leucine at position 697 of the mature subunit of vWF. We reproduced this mutation in vWF cDNA and expressed the recombinant protein in Cos-7 cells. The subunit composition and multimeric structure of mutated protein (rvWFLeu697Val) were similar to the wild-type recombinant (WTrvWF). Ristocetin-induced binding of rvWFLeu697Val to platelets was markedly increased in the presence of low doses of ristocetin and slightly increased with botrocetin as compared with that for WTrvWF, whereas collagen binding was not affected by the mutation. These data show that the Leu 697-->Val substitution is not a rare polymorphism but is responsible for the subtype IIB characteristic abnormalities identified in the two affected patients; however, it is not located in the area of vWF (amino acid 540 to amino acid 578) where most of the other type IIB mutations have already been reported.

Molecular and cellular biology of von Willebrand factor.

Handin RI, Wagner DD
Prog Hemost Thromb. 1989; 9: 233-59

Instability in the ATCT variable number tandem repeat locus VWF.VNTR I in intron 40 of von Willebrand factor gene.

Haddad AP, Sparrow RL
Br J Haematol. 1997; 98: 662-4

The von Willebrand factor gene intron 40 variable number tandem repeat VWF.VNTR I exhibits 10 alleles making it highly polymorphic and useful for parentage and forensic testing, 45 unrelated families (210 meiotic events) were tested for VWF.VNTR I alleles. One spontaneous mutation was observed in a family member. Haplotype analysis demonstrated that this mutation was due to a gain of one motif repeat by a paternal allele. Sequence analysis confirmed the difference in the number of motif repeats between the proband and the alleles expressed by the parents. This instability emphasizes the importance of demonstrating exclusion in at least two separate loci in parentage testing.

von Willebrand factor storage and multimerization: 2 independent intracellular processes.

Haberichter SL, Fahs SA, Montgomery RR
Blood. 2000; 96: 1808-15

The von Willebrand factor propeptide, vW AgII, has been shown to be required for the formation of vWF multimers and sorting of vWF to storage granules; whether these 2 processes are independent events has been unclear. Chimeric constructs of human and canine vWF were developed to further define these processes and to determine whether they are independent intracellular events. Cells expressing only mature vWF (Deltapro) produced vWF dimers that were not stored in AtT-20 cells; whereas the expression of vW AgII alone resulted in vW AgII granular storage. Expression of vW AgII in trans with Deltapro resulted in the multimerization of vWF and colocalized storage of vW AgII and vWF. Expression of canine vW AgII in trans or cis with human Deltapro resulted in the multimerization of human vWF, with no storage of human vWF but with normal storage of canine vW AgII. This dissociation of functions indicates that the signals for multimerization of vWF are different from the signals for trafficking of vWF to storage and demonstrates that vWF storage and multimerization are 2 independent intracellular processes. vW AgII contains the signal(s) required for trafficking to storage, and only through interaction with vW AgII is vWF chaperoned into granules. (Blood. 2000;96:1808-1815)

Molecular cloning of human intestinal mucin (MUC2) cDNA. Identification of the amino terminus and overall sequence similarity to prepro-von Willebrand factor.

Gum JR Jr, Hicks JW, Toribara NW, Siddiki B, Kim YS
J Biol Chem. 1994; 269: 2440-6

Secretory mucins consist of a protein backbone that is catenated by disulfide bonds, heavily O-glycosylated, and packaged into storage granules prior to release from cells. In this paper, we identify and sequence cDNAs that encode the amino terminus of the MUC2 protein, a major form of mucin found in human intestines and airways. The protein sequence was found to contain a repetitive element of approximately 350 amino acids with considerable sequence similarity to the D domains of prepro-von Willebrand factor. A total of four of these D domains were found to be present in the MUC2 protein, three in the amino-terminal region, and one in the carboxyl-terminal region. Prepro-von Willebrand factor contains four D domains itself, and the overall positioning of the D domains in the two proteins is similar. Prepro-von Willebrand factor contains a 741 residue pro-protein that has been implicated in both the disulfide-linked oligomerization of von Willebrand factor and its packaging into secretory vacuoles. A similar region is present in the MUC2 amino terminus sequence, suggesting that the mechanisms involved in the polymerization and packaging of MUC2 may parallel those already described for von Willebrand factor.

The human MUC2 intestinal mucin has cysteine-rich subdomains located both upstream and downstream of its central repetitive region.

Gum JR Jr, Hicks JW, Toribara NW, Rothe EM, Lagace RE, Kim YS
J Biol Chem. 1992; 267: 21375-83

The human MUC2 mucin is a large secretory glycoconjugate that coats the epithelia of the intestines, airways, and other mucus membrane-containing organs. Previous work has shown that this mucin contains an extended tandem repeat-containing domain rich in Thr and Pro. In the present work we describe two additional regions of this mucin located both upstream and downstream of the tandem repeat array. The carboxyl-terminal domain contains 984 residues and can be divided into mucin-like (139 residues) and cysteine-rich (845 residues) subdomains. This latter subdomain exhibits varying degrees of sequence similarity to a wide range of mucins and mucin-like proteins including those isolated from rats, pigs, cows, and frogs. We also report here the sequence of 1270 residues lying immediately upstream of the tandem repeats. This region contains a repetitive, mucin-like subdomain and a second cysteine-rich stretch of more than 700 residues. Both cysteine-rich subdomains of this mucin have sequence similarity with von Willebrand factor, a serum protein that exists as a disulfide-linked polymer. This suggests that these cysteine-rich subdomains are important in the catenation of mucin monomers into oligomers, the structures that confer viscoelasticity upon mucus.

A Drosophila haemocyte-specific protein, hemolectin, similar to human von Willebrand factor.

Goto A, Kumagai T, Kumagai C, Hirose J, Narita H, Mori H, Kadowaki T, Beck K, Kitagawa Y
Biochem J. 2001; 359: 99-108

We identified a novel Drosophila protein of approximately 400 kDa, hemolectin (d-Hml), secreted from haemocyte-derived Kc167 cells. Its 11.7 kbp cDNA contains an open reading frame of 3843 amino acid residues, with conserved domains in von Willebrand factor (VWF), coagulation factor V/VIII and complement factors. The d-hml gene is located on the third chromosome (position 70C1-5) and consists of 26 exons. The major part of d-Hml consists of well-known motifs with the organization: CP1-EG1-CP2-EG2-CP3-VD1-VD2-VD'-VD3-VC1-VD"-VD"'-FC1-FC2-VC2-LA1-VD4-VD5-V C3-VB1-VB2-VC4-VC5-CK1 (CP, complement-control protein domain; EG, epidermal-growth-factor-like domain; VB, VC, VD, VWF type B-, C- and D-like domains; VD', VD", VD"', truncated C-terminal VDs; FC, coagulation factor V/VIII type C domain; LA, low-density-lipoprotein-receptor class A domain; CK, cysteine knot domain). The organization of VD1-VD2-VD'-VD3, essential for VWF to be processed by furin, to bind to coagulation factor VIII and to form interchain disulphide linkages, is conserved. The 400 kDa form of d-Hml was sensitive to acidic cleavage near the boundary between VD2 and VD', where the cleavage site of pro-VWF is located. Agarose-gel electrophoresis of metabolically radiolabelled d-Hml suggested that it is secreted from Kc167 cells mainly as dimers. Resembling VWF, 7.9% (305 residues) of cysteine residues on the d-Hml sequence had well-conserved positions in each motif. Coinciding with the development of phagocytic haemocytes, d-hml transcript was detected in late embryos and larvae. Its low-level expression in adult flies was induced by injury at any position on the body.

Human von Willebrand factor (vWF): isolation of complementary DNA (cDNA) clones and chromosomal localization.

Ginsburg D, Handin RI, Bonthron DT, Donlon TA, Bruns GA, Latt SA, Orkin SH
Science. 1985; 228: 1401-6

Human factor VIII--von Willebrand factor (vWF) is a large, multimeric glycoprotein that plays a central role in the blood coagulation system, serving both as a carrier for factor VIIIC (antihemophilic factor) and as a major mediator of platelet-vessel wall interaction. Diminished or abnormal vWF activity results in von Willebrand's disease (vWD), a common and complex hereditary bleeding disorder. Overlapping vWF cDNA clones that span 8.2 kilobases of the vWF messenger RNA have been obtained. vWF accounts for approximately 0.3 percent of endothelial cell messenger RNA and was undetectable in several other tissues examined. A large single copy gene for vWF is located on the short arm of chromosome 12 (12p12----12pter). No gross gene rearrangement or deletion was detected in the DNA of two patients with severe vWD.

Molecular genetics of von Willebrand disease.

Ginsburg D
Thromb Haemost. 1999; 82: 585-91

A novel mutation (Leu817Pro) causing type 2A von Willebrand disease.

Gemmati D, Serino ML, Moratelli S, Ballerini G, Furbetta M, Lunghi B, Marchetti G, Bernardi F
Br J Haematol. 1996; 92: 241-3

We studied a patient affected by von Willebrand disease type 2A who experienced several mild bleeding episodes and was characterized by markedly reduced haemostatic parameters. In the exon 28 of von Willebrand factor (vWF) gene a T to C transition at nucleotide 8680, resulting in the missense mutation Leu817Pro, was found in the heterozygous form in the patient and in two affected relatives. As suggested by the presence in platelets of a complete spectrum of vWF multimers as well as by the increased vWF antigen levels and improved haemostasis after DDAVP treatment, the mutation is compatible with normal multimerization, and could be responsible for a reduced stability or an impaired physiological secretion of vWF.

Characterization of von Willebrand factor gene defects in two unrelated patients with type IIC von Willebrand disease.

Gaucher C, Dieval J, Mazurier C
Blood. 1994; 84: 1024-30

Genetic studies were performed in two unrelated patients with the IIC phenotype of von Willebrand disease (vWD) characterized by the increased concentration of the protomeric form of von Willebrand factor (vWF). In patient B, the sequencing of both exons 15 and 16 of the vWF gene showed two sequence alterations: a 3-bp insertion in exon 15 resulting in the insertion of a Glycine at position 625 (625insGly) and a 2-bp deletion in exon 16 leading to a premature translational stop at codon 711 (711 ter), at the heterozygote state. Patient A was found homozygous for a single point mutation also localized in exon 15 and responsible for the substitution Cys623Trp. These candidate mutations were not found in a panel of 96 normal chromosomes, suggesting a causal relationship with IIC vWD phenotypic expression. The composite heterozygote or homozygote state of both patients supports the recessive mode of inheritance already described for this phenotype. Furthermore, the localization of these gene defects in the D2 domain of vWF propeptide, known to play an important role in vWF multimerization, provides another argument in favor of their causative effect regarding the peculiar multimeric pattern of vWF in these patients.

Diagnosis of subtype 2B von Willebrand disease in a patient with 2A phenotype of plasma von Willebrand factor.

Gaucher C, de Romeuf C, Rauis-Morret M, Corazza F, Fondu P, Mazurier C
Thromb Haemost. 1995; 73: 610-6

Type 2A of von Willebrand disease refers to qualitative variants with decreased platelet dependent function that is associated with the absence of high molecular weight forms of von Willebrand factor (vWF) multimers. Type 2B refers to qualitative variants with increased affinity for platelet glycoprotein Ib. In this report we describe the study of a patient who has been previously diagnosed as having subtype 2A von Willebrand disease (vWD), because she had no heightened ristocetin-induced platelet aggregation, no large and intermediate molecular weight von Willebrand factor (vWF) multimers in plasma, and no increase in plasma vWF capacity to bind to normal platelets in the presence of low ristocetin concentrations. The DNA sequencing of the 3' part of the exon 28 of the vWF gene where most of the subtype 2A mutations have already been identified, did not detect any nucleotide change. At variance, a G to A transition changing the encoded amino acid residue from Val 553 to Met in mature vWF, was found in the 5' part of this exon. This mutation which has already been found in several unrelated families with 2B vWD and the increased binding of the patient platelet vWF on normal platelets in the presence of low ristocetin concentrations provide evidence for subtype 2B vWD. This study thus illustrates the importance of the molecular characterization of patients in the correct diagnosis and classification of type 2 vWD.

[Molecular structure and genetic analysis of the von Willebrand factor]

Fukutake K, Fujimaki M
Nippon Rinsho. 1987; 45: 2947-53

von Willebrand factor: its function and its measurement in the laboratory.

Fleming TG
Br J Biomed Sci. 1995; 52: 50-7

von Willebrand factor (vWF) is a complex protein essential to normal haemostasis. It is vital to platelet adhesion in the high shear stress conditions encountered in the small blood vessels. Deficient overall levels of, or the presence of abnormally functioning variants of, vWF lead to the common bleeding disorder termed von Willebrand's disease. Laboratory investigation is aimed at both quantitative and qualitative investigation with a view to classification of the abnormality for each individual patient into a particular sub-type.

Propolypeptide of von Willebrand factor circulates in blood and is identical to von Willebrand antigen II.

Fay PJ, Kawai Y, Wagner DD, Ginsburg D, Bonthron D, Ohlsson-Wilhelm BM, Chavin SI, Abraham GN, Handin RI, Orkin SH, et al.
Science. 1986; 232: 995-8

The generally mild bleeding disorder of von Willebrand disease is associated with abnormalities of two distinct plasma proteins, the large multimeric von Willebrand factor (vWF), which mediates platelet adhesion, and von Willebrand antigen II (vW AgII), which is of unknown function. The two proteins were found to have a common biosynthetic origin in endothelial cells and megakaryocytes, which explains their simultaneous absence in the severe form of this hereditary disease. Shared amino acid sequences from a 100-kilodalton plasma glycoprotein and from vW AgII are identical to amino acid sequences predicted from a complementary DNA clone encoding the 5' end of vWF. In addition, these proteins have identical molecular weights and immunologic cross reactivities. Monoclonal antibodies prepared against both proteins recognize epitopes on the pro-vWF subunit and on a 100-kilodalton protein that are not present on the mature vWF subunit in endothelial cell lysates. In contrast, polyclonal antibodies against vWF recognize both pro-vWF and vWF subunits. Thus, the 100-kilodalton plasma glycoprotein and vW AgII are identical proteins and represent an extremely large propolypeptide that is first cleaved from pro-vWF during intracellular processing and then released into plasma.

Human mucin gene MUC5AC: organization of its 5'-region and central repetitive region.

Escande F, Aubert JP, Porchet N, Buisine MP
Biochem J. 2001; 358: 763-72

Human mucin gene MUC5AC is clustered with MUC2, MUC5B and MUC6 on chromosome 11p15.5. We report here the full length cDNA sequence upstream of the repetitive region of human MUC5AC. We have also determined the sequence of its large central tandem repeat array. The 5'-region reveals high degree of sequence similarity with MUC2 and MUC5B and codes for 1336 amino acids organized into a signal peptide, four pro-von Willebrand factor-like D domains (D1, D2, D' and D3) and a short domain which connects to the central repetitive region. In the central region, 17 major domains have been identified. Nine code for cysteine-rich domains (Cys-domains 1-9) and exhibit high sequence similarity to the cysteine-rich domains described in the central region of MUC2 and MUC5B. Cys-domains 1-5 are interspersed by domains enriched with serine, threonine, and proline residues. Cys-domains 1-9 are interspersed by four domains (TR1-TR4) composed of various numbers of MUC5AC-type repeats. Southern-blot analyses reveal allelic variations both in length and nucleotide sequence. The length polymorphism which is due to variable numbers of tandem repeats is located in TR1 and TR4, whereas a mutation polymorphism detected with TaqI is located in Cys-domain 6. In this study, the organization of MUC5AC has been entirely elucidated showing extensive similarity to the other chromosome 11p15 MUC genes, particularly MUC5B, and providing additional arguments for common evolution from a single ancestral gene.

Analysis of Arg834Gln and Val902Glu type 2A von Willebrand disease mutations: studies with recombinant von Willebrand factor and correlation with patient characteristics.

Englender T, Lattuada A, Mannucci PM, Sadler JE, Inbal A
Blood. 1996; 87: 2788-94

Type 2A von Willebrand disease (vWD), the most common qualitative form of vWD, is characterized by a relative decrease in circulating intermediate and high molecular weight (HMW) multimers. We studied the biosynthesis of recombinant von Willebrand factor (vWF) containing each of two type 2A vWD mutations previously reported by us, Arg834Gln and Val902Glu. The structure of recombinant Arg834Gln vWF within transfected COS-7 cells and the secretion of HMW multimers were similar to wild type vWF. The normal transport and secretion of Arg834Gln vWF, categorizes it as a group II type 2A mutation. In contrast, the Val90-2Glu mutation resulted in intracellular proteolysis of vWF with the generation of a 176-kD fragment and retention of vWF between the endoplasmic reticulum and the Golgi complex. Moreover, the 176-kD fragment was also increased in plasma from patients with the Val902Glu mutation. Significantly impaired secretion and intracellular proteolysis of Val902Glu vWF categorizes a new sub-group of type 2A mutations. The intracellular proteolysis of vWF Val902Glu explains the lack of response to 1-deamino 8-D-arginine vasopressin (DDAVP) in patients who carry the mutation.

Multiple substitutions in the von Willebrand factor gene that mimic the pseudogene sequence.

Eikenboom JC, Vink T, Briet E, Sixma JJ, Reitsma PH
Proc Natl Acad Sci U S A. 1994; 91: 2221-4

We have analyzed a type IIB and a type I von Willebrand disease family for the presence of mutations in the region coding for the glycoprotein Ib binding domain of the von Willebrand factor. Since this sequence is also present in the highly homologous von Willebrand factor pseudogene, we have studied genomic DNA as well as cDNA, which was produced from RNA isolated from endothelial cells or platelets. In both families, we have detected multiple consecutive nucleotide substitutions in the 5' end of exon 28 that result in a sequence identical to the von Willebrand factor pseudogene. These substitutions were also found in cDNA, which proves that they are present in the active gene. The occurrence of multiple adjacent substitutions that exactly reflect a part of the sequence of the von Willebrand factor pseudogene is difficult to reconcile with sequential single mutational events. We therefore hypothesize that each of these multiple substitutions arose from one recombinational event between gene and pseudogene.

Instability of repeats of the von Willebrand factor gene variable number tandem repeat sequence in intron 40.

Eikenboom JC, Reitsma PH, van der Velden PA, Briet E
Br J Haematol. 1993; 84: 533-5

The von Willebrand factor gene contains a highly polymorphic variable number tandem repeat sequence (VNTR) in intron 40. We observed the spontaneous mutation to a new length allele. Sequence analysis revealed that the change in length corresponds to one tetranucleotide repeat unit. This observation emphasizes the risk of errors in family studies and prenatal diagnosis due to VNTR instability.

Dominant type 1 von Willebrand disease caused by mutated cysteine residues in the D3 domain of von Willebrand factor.

Eikenboom JC, Matsushita T, Reitsma PH, Tuley EA, Castaman G, Briet E, Sadler JE
Blood. 1996; 88: 2433-41

No defects have been reported in moderately severe type 1 von Willebrand disease (vWD) with a clear autosomal dominant inheritance pattern, and the mechanism underlying this form of vWD remains obscure. We have studied a type 1 vWD family with such a dominant phenotype. The entire coding sequence of the von Willebrand factor (vWF) gene was analyzed by direct sequencing of DNA fragments amplified by polymerase chain reaction. Only one candidate mutation T(3445)-->C in exon 26 was detected that predicts a replacement of cysteine (C) at position 386 of the mature vWF subunit by arginine (R). Both mutant and normal vWF alleles were expressed as shown by analysis of platelet mRNA. This substitution segregates with vWD in the family and was not found in 100 unrelated individuals. The recombinant mutant vWF(C386R) was characterized by expression in 293T cells. The secretion of vWF(C386R) was greatly impaired due to retention in the endoplasmic reticulum. In cotransfections of normal and mutant vWF constructs, the vWF(C386R) subunits caused a dose-dependent decrease in the secretion of vWF. The multimer pattern remained nearly normal and consistent with a dominant vWD type 1 phenotype. The importance of the cysteine residues in the D3 domain of vWF in the pathogenesis of dominant type 1 vWD was further shown by the detection of another cysteine mutation, Cys367-->Phe, in two additional unrelated patients with a similar dominant type 1 vWD phenotype. We conclude that the loss of cysteine pairing in the D3 domain, leaving one free cysteine, can induce a purely quantitative deficiency of vWF by dominantly suppressing the secretion of normal vWF.

Hypothyroidism and von Willebrand factor.

Dodds WJ
J Am Vet Med Assoc. 1995; 206: 594-6

Evolution of the large secreted gel-forming mucins.

Desseyn JL, Aubert JP, Porchet N, Laine A
Mol Biol Evol. 2000; 17: 1175-84

Mucins, the major component of mucus, contain tandemly repeated sequences that differ from one mucin to another. Considerable advances have been made in recent years in our knowledge of mucin genes. The availability of the complete genomic and cDNA sequences of MUC5B, one of the four human mucin genes clustered on chromosome 11, provides an exemplary model for studying the molecular evolution of large mucins. The emerging picture is one of expansion of mucin genes by gene duplications, followed by internal repeat expansion that strictly preserves frameshift. Computational and phylogenetic analyses have permitted the proposal of an evolutionary history of the four human mucin genes located on chromosome 11 from an ancestor gene common to the human von Willebrand factor gene and the suggestion of a model for the evolution of the repeat coding portion of the MUC5B gene from a hypothetical ancestral minigene. The characterization of MUC5B, a member of the large secreted gel-forming mucin family, offers a new model for the comparative study of the structure-function relationship within this important family.

Heparin binding assay of von Willebrand factor (vWF) in plasma milieu--evidence of the importance of the multimerization degree of vWF.

de Romeuf C, Mazurier C
Thromb Haemost. 1993; 69: 436-40

We developed a simple and fast method for studying the heparin binding of von Willebrand factor (vWF) in the plasma milieu. Using plasma from patients with von Willebrand disease (vWD) subtype II, we found that the heparin binding was impaired when compared with a normal plasma control. Further experiments performed with purified vWF of various multimeric composition, obtained either by gradual reduction or gel filtration, confirmed that heparin binding is dependent on the multimerization of vWF and that high molecular weight (HMW) multimers of vWF are required for normal heparin binding. After reduction of plasma vWF by 1.5 mM DTT, the vWF monomer still binds to heparin but to a lower extent. Under these conditions, no significant differences were obtained between control and patients showing that the heparin binding domain located on the vWF subunit is not altered in the subtypes IIA, IIB and IIC studied.

Interaction of the von Willebrand factor (vWF) with collagen. Localization of the primary collagen-binding site by analysis of recombinant vWF A domain polypeptides.

Cruz MA, Yuan H, Lee JR, Wise RJ, Handin RI
J Biol Chem. 1995; 270: 19668-19668

The superfamily of proteins with von Willebrand factor type A-like domains: one theme common to components of extracellular matrix, hemostasis, cellular adhesion, and defense mechanisms.

Colombatti A, Bonaldo P
Blood. 1991; 77: 2305-15

Molecular cloning of the human gene for von Willebrand factor and identification of the transcription initiation site.

Collins CJ, Underdahl JP, Levene RB, Ravera CP, Morin MJ, Dombalagian MJ, Ricca G, Livingston DM, Lynch DC
Proc Natl Acad Sci U S A. 1987; 84: 4393-7

A series of overlapping cosmid genomic clones have been isolated that contain the entire coding unit of the human gene for von Willebrand factor (vWf), a major component of the hemostatic system. The cloned segments span approximately 175 kilobases of human DNA sequence, and hybridization analysis suggests that the vWf coding unit is approximately 150 kilobases in length. Within one of these clones, the vWf transcription initiation site has been mapped and a portion of the vWf promoter region has been sequenced, revealing a typical "TATA box," a downstream "CCAAT box," and a perfect downstream repeat of the 8 base pairs containing the transcription start site. Sequencing of a segment of another genomic clone has revealed the vWf translation termination codon. Where tested, comparative restriction analysis of cloned and chromosomal DNA segments strongly suggests that no major alterations occurred during cloning and that there is only one complete copy of the vWf gene in the human haploid genome. Similar analyses of DNA from vWf-producing endothelial cells and nonexpressing leukocytes suggest that vWf gene expression is not accompanied by gross genomic rearrangements. In addition, there is significant homology of C-terminal coding sequences among the vWf genes of several vertebrate species.

Mosaic structure of globular domains in the human type VI collagen alpha 3 chain: similarity to von Willebrand factor, fibronectin, actin, salivary proteins and aprotinin type protease inhibitors.

Chu ML, Zhang RZ, Pan TC, Stokes D, Conway D, Kuo HJ, Glanville R, Mayer U, Mann K, Deutzmann R, et al.
EMBO J. 1990; 9: 385-93

Human collagen alpha 3(VI) chain mRNA (approximately 10 kb) was cloned and shown by sequence analysis to encode a 25 residue signal peptide, a large N-terminal globule (1804 residues), a central triple helical segment (336 residues) and a C-terminal globule (803 residues). Some of the sequence was confirmed by Edman degradation of peptides. The N-terminal globular segment consists of nine consecutive 200 residue repeats (N1 to N9) showing internal homology and also significant identity (17-25%) to the A domains of von Willebrand Factor and similar domains present in some other proteins. Deletions were found in the N3 and N9 domains of several cDNA clones suggesting variation of these structures by alternative splicing. The C-terminal globule starts immediately after the triple helical segment with two domains C1 (184 residues) and C2 (248 residues) being similar to the N domains. They are followed by a proline rich, repetitive segment C3 of 122 residues, with similarity to some salivary proteins, and domain C4 (89 residues), which is similar to the type III repeats present in fibronectin and tenascin. The most C-terminal domain C5 (70 residues) shows 40-50% identity to a variety of serine protease inhibitors of the Kunitz type. The whole sequence contains 29 cysteines which are mainly clustered in short segments connecting domains N1, C1, C2 and the triple helix, and in the inhibitor domain. Five putative Arg-Gly-Asp cell-binding sequences are exclusively localized in the triple helical segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequence analysis of alpha 1(VI) and alpha 2(VI) chains of human type VI collagen reveals internal triplication of globular domains similar to the A domains of von Willebrand factor and two alpha 2(VI) chain variants that differ in the carboxy terminus.

Chu ML, Pan TC, Conway D, Kuo HJ, Glanville RW, Timpl R, Mann K, Deutzmann R
EMBO J. 1989; 8: 1939-46

Amino acid sequences of human collagen alpha 1(VI) and alpha 2(VI) chains were completed by cDNA sequencing and Edman degradation demonstrating that the mature polypeptides contain 1009 and 998 amino acid residues respectively. In addition, they contain small signal peptide sequences. Both chains show 31% identity in the N-terminal (approximately 235 residues) and C-terminal (approximately 430 residues) globular domains which are connected by a triple helical segment (335-336 residues). Internal alignment of the globular sequences indicates a repetitive 200-residue structure (15-23% identity) occurring three times (N1, C1, C2) in each chain. These repeating subdomains are connected to each other and to the triple helix by short (15-30 residues) cysteine-rich segments. The globular domains possess several N-glycosylation sites but no cell-binding RGD sequences, which are exclusively found in the triple helical segment. Sequencing of alpha 2(VI) cDNA clones revealed two variant chains with a distinct C2 subdomain and 3' non-coding region. The repetitive segments C1, C2 and, to a lesser extent, N1 show significant identity (15-18%) to the collagen-binding A domains of von Willebrand factor (vWF) and they are also similar to some integrin receptors, complement components and a cartilage matrix protein. Since the globular domains of collagen VI come into close contact with triple helical segments during the formation of tissue microfibrils it suggests that the globular domains bind to collagenous structures in a manner similar to the binding of vWF to collagen I.

Grossly abnormal proteolysis of von Willebrand factor (VWF) in a patient heterozygous for a gene deletion and mutation in the dimerization area of VWF.

Castaman G, Eikenboom JC, Lattuada A, Rodeghiero F
Thromb Haemost. 2000; 84: 729-30

Heightened proteolysis of the von Willebrand factor subunit in patients with von Willebrand disease hemizygous or homozygous for the C2362F mutation.

Castaman G, Eikenboom JC, Lattuada A, Mannucci PM, Rodeghiero F
Br J Haematol. 2000; 108: 188-90

We studied the proteolytic pattern of the mutant von Willebrand factor (VWF) in four patients with von Willebrand disease (VWD) who were either homozygous or hemizygous for the mutation C2362F. A significant decrease in the native fragment of 225 kDa was evident in all the patients, together with a marked increase in the 176 and 140 kDa fragments, a pattern usually observed in type 2A VWD. The proteolytic pattern measured in four heterozygotes for C2362F was within the normal range, suggesting that the mutant VWF C2362F present in the plasma of these patients may be protected from proteolysis by normal VWF.

Which assay is the most suitable to investigate von Willebrand factor functional activity?

Casonato A, Pontara E, Bertomoro A, Sartorello F, Girolami A
Thromb Haemost. 1999; 81: 994-5

Instability of a variable number tandem repeat in intron 40 of the human von Willebrand factor gene.

Casana P, Martinez F, Aznar JA
Br J Haematol. 1995; 91: 255-6

Structure of pre-pro-von Willebrand factor and its expression in heterologous cells.

Bonthron DT, Handin RI, Kaufman RJ, Wasley LC, Orr EC, Mitsock LM, Ewenstein B, Loscalzo J, Ginsburg D, Orkin SH
Nature. 1986; 324: 270-3

Von Willebrand factor (vWF), a multifunctional haemostatic glycoprotein derived from endothelial cells and megakaryocytes, mediates platelet adhesion to injured subendothelium and binds coagulation factor VIII in the circulation. Native vWF is a disulphide-bonded homopolymer; the monomeric subunits, of apparent relative molecular mass (Mr) 220,000 (220K) are derived from an intracellular precursor estimated at 260-275K. Multimer assembly is preceded by the formation of dimers, linked near their C-termini, which then assemble into filamentous polymers. The importance of the removal of the large vWF pro-polypeptide during multimer assembly, and whether this or other stages of the complex post-translational processing require components specific to endothelial cells or megakaryocytes, is unknown. Here we report an analysis of the complete sequence of pre-pro-vWF and expression of the molecule in heterologous cells. The vWF precursor is composed of several repeated subdomains. When expressed in COS and CHO cells, it is cleaved and assembled into biologically active high relative molecular mass disulphide bonded multimers. This suggests that the information for assembly of this complex molecule resides largely within its primary structure.

Nucleotide sequence of pre-pro-von Willebrand factor cDNA.

Bonthron D, Orr EC, Mitsock LM, Ginsburg D, Handin RI, Orkin SH
Nucleic Acids Res. 1986; 14: 7125-7

The human von Willebrand factor gene. Structure of the 5' region.

Bonthron D, Orkin SH
Eur J Biochem. 1988; 171: 51-7

Von Willebrand factor (vWF) is a multimeric glycoprotein product of endothelial cells and platelets, that is important for normal hemostasis. Recently the complete primary structure of the vWF precursor was deduced from cloned complementary DNAs (cDNAs). To approach the analysis of DNA elements that mediate tissue-specific expression, we have characterized the region of the human vWF gene surrounding the transcriptional initiation site, and including the first five exons. The putative vWF promoter region includes an (A + T)-rich 'TATA'-like element approximately 30 bp upstream of the transcription start site, but no CCAAT or 'GC' box elements (typical motifs of other promoters). A (GT)n repeat element of uncertain significance is located about 650 bp farther upstream. The DNA sequence of the 5' flanking region suggests the presence of potentially novel elements involved in regulation of the restricted expression of vWF.

Alpha 1 chain of chick type VI collagen. The complete cDNA sequence reveals a hybrid molecule made of one short collagen and three von Willebrand factor type A-like domains.

Bonaldo P, Russo V, Bucciotti F, Bressan GM, Colombatti A
J Biol Chem. 1989; 264: 5575-80

A cDNA library constructed from chick aorta poly(A+) RNA in the expression vector pEX1 was screened with rabbit polyclonal antisera. Additional clones were obtained by DNA-DNA hybridization with subclones from the most 5'- and 3'-ends. The overlapping clones span 4.6 kilobases and code for the entire alpha 1 (VI) chain. The nucleotide sequence reveals a 3057-base pair open reading frame that codes for 1019 amino acids. Analysis of the deduced amino acid sequence predicts that alpha 1 (VI) has one collagenous domain (COL) of 336 residues flanked by three repeated domains of about 200 residues each, one at the amino (A'3) and two at the carboxyl ends (A'2 and A'1), respectively, that are similar to the type A repeats of von Willebrand Factor. The COL domain presents two short interruptions near the carboxyl end of the triple helix and three of the six potential N-asparaginyl-linked carbohydrate attachment sites (Asn-Xaa-Ser/Thr). Furthermore, it contains 1 cysteine at position 89 that could participate in the formation of dimers and 3 Arg-Gly-Asp sequences that might be potential sites for cell adhesion. The COL domain shows an extended region, starting from position 40, within the triple helix, made of 14 Gly-Xaa-Yaa triplets that lack proline in the Y position, suggesting that it might be more flexible than the rest of the domain. At the junction of the COL with the N- and C-terminal domains, there are several cysteines that could confer the well known resistance of type VI collagen to pepsin and collagenase digestion under nonreducing conditions. The present sequence data allow a structural model for type VI collagen assembly to be proposed that is consistent with the structure implied from previous electron microscopic observation by Furthmayr et al. (Furthmayr, H., Wiedemann, H., Timpl, R., Odermatt, R., and Engel, J. (1983) Biochem. J. 221, 303-311).

Postural variation in von Willebrand factor antigen.

Blann A, Jayson MI, Pope MH, Kaigle AM, Wilder D, Weinstein JN
Ann Rheum Dis. 1993; 52: 82-82

von Willebrand factor in upper gastrointestinal tract inflammation.

Blann AD
Gut. 1993; 34: 288-288

von Willebrand factor and atherosclerosis.

Blann AD
Circulation. 1993; 88: 1962-3

In-frame deletion of von Willebrand factor A domains in a dominant type of von Willebrand disease.

Bernardi F, Patracchini P, Gemmati D, Pinotti M, Schwienbacher C, Ballerini G, Marchetti G
Hum Mol Genet. 1993; 2: 545-8

von Willebrand disease (vWD), the most common inherited bleeding disorder in humans, is very heterogeneous and has been classified into several subtypes. Missense mutations have been found to be responsible for the dominant type II vWD, characterized by qualitative abnormalities affecting von Willebrand factor (vWF) function. The breakpoints of a heterozygous vWF gene deletion (31 Kb), occurring 'de novo' in a patient with a variant of type II vWD, were localized to introns 25 and 34 and sequenced. An Alu repeat in intron 25 was interrupted between the transcriptional boxes A and B. The new junction present in the abnormal von Willebrand factor mRNA was sequenced after reverse transcription of platelet RNA. The codon 1104 (Cys) is followed in frame by the mutated codon 1926 (Cys to Arg), thus removing the complete A domains, found in a wide variety of genes and characterized by independent assembly 'in vitro'. We propose that the abnormal vWF, which carries intact protein domains responsible for vWF dimer and multimer formation, makes ineffective interactions with the normal molecules in the biosynthetic process, causing the dominant type II phenotype through a novel mechanism.

Proteolytic processing of von Willebrand factor subunit: heterogeneity in type-IIA von Willebrand disease.

Batlle J, Lasierra J, Villamor AF, Navarro JL, Pardo A, Campos M, Justica B, Lopez Fernandez MF
Ann Hematol. 1994; 68: 111-5

Type IIA von Willebrand disease (vWD) is a heterogeneous disorder for which two different pathogenetic mechanisms have been proposed: increased proteolytic susceptibility of von Willebrand factor (vWF), and/or interference of its post-translational processing. Subunit analysis of vWF in type-IIA vWD has revealed an increased relative proportion of the 176- and 140-kDa subunit-derived fragments, suggesting an augmented fragmentation of vWF, even in the resting state. We analyzed the subunit pattern of vWF in plasma from five previously described patients with type-IIA vWD. All of them showed the above-mentioned pattern. In addition, the presence of a new band with an apparent molecular mass of 200 kDa, not described in normal individuals or in patients with vWD, was repeatedly observed in one of these patients. This patient also exhibited an abnormal vWF multimeric structure in platelets and in plasma, before and after desmopressin administration, when the blood was collected either in the presence or in the absence of proteinase inhibitors. We believe that an abnormal primary structure of vWF could be responsible for this abnormal proteolytic fragmentation pattern, as well as for the abnormal multimerization of vWF. Moreover, an abnormal susceptibility to proteolysis appears to be present, as suggested by the increase in the relative proportion of the 176-kDa fragment observed in the same patient. Future sequencing studies and genetic analysis may clarify whether there are one or two different defects related to the vWF of that patient. Our results indicate that the subunit analysis of vWF may reveal additional defects present in type-IIA vWD that may help our understanding of the pathogenesis of such disease.

Sequencing of the primary adhesion domain of bovine von Willebrand factor.

Bakhshi MR, Myers JC, Howard PS, Soprano DR, Kirby EP
Biochim Biophys Acta. 1992; 1132: 325-8

A cDNA library, constructed from bovine heart endothelial cell poly(A)+ RNA, was screened using a BstXI fragment of human von Willebrand and factor (vWF) cDNA as a probe. This probe codes for the major adhesion domain of vWF that includes the GPIb, collagen and heparin binding domains. Of the ten positive clones obtained, a clone that spanned the region of interest was sequenced by the dideoxynucleotide method yielding a sequence of 1550 bp. This region of the bovine cDNA codes for amino acids corresponding to #262 to #777 in human vWF and encompasses the entire pro adhesion domain. Both the nucleotide sequence and the deduced amino acid sequence are 82% homologous to those of human vWF. Cysteine residues #471, 474, 509 and 695, which form intrachain bonds in human vWF, are also present in the bovine vWF sequence.

Invertebrate vitellogenin is homologous to human von Willebrand factor.

Baker ME
Biochem J. 1988; 256: 1059-61

The human gene for von Willebrand factor. Identification of repetitive Alu sequences 5' to the transcription initiation site.

Assouline Z, Kerbiriou-Nabias DM, Pietu G, Thomas N, Bahnak BR, Meyer D
Biochem Biophys Res Commun. 1988; 153: 1159-66

The region at the 5' end of von Willebrand factor gene was cloned by screening genomic libraries with a partial von Willebrand factor cDNA probe and oligonucleotides complementary to areas of von Willebrand factor mRNA at the extreme 5' end of the untranslated region. The sequence 2158 bp upstream of the transcription initiation site, the first exon and first exon-intron junction is reported. The first exon includes the entire 5' untranslated sequence (250 bp) and the translation initiation codon starts the second exon, suggesting an unusual control mechanism for the cell specific expression of von Willebrand factor. An AT-rich region resembling a TATA box is found 32 bp upstream of the transcription initiation site. At -1030 and -1806 nucleotides 5' of the TATA box are two repetitive Alu sequences of approximately 300 bp. Recombinant events at these Alu sequences could result in some clinical forms of von Willebrand disease involving transcriptional defects.

A novel von Willebrand disease-causing mutation (Arg273Trp) in the von Willebrand factor propeptide that results in defective multimerization and secretion.

Allen S, Abuzenadah AM, Hinks J, Blagg JL, Gursel T, Ingerslev J, Goodeve AC, Peake IR, Daly ME
Blood. 2000; 96: 560-8

In this report we describe the molecular defect underlying partial and severe quantitative von Willebrand factor (VWF) deficiencies in 3 families previously diagnosed with types 1 and 3 Von Willebrand-disease. Analysis of the VWF gene in affected family members revealed a novel C to T transition at nucleotide 1067 of the VWF complemetary DNA (cDNA), predicting substitution of arginine by tryptophan at amino acid position 273 (R273W) of pre-pro-VWF. Two patients, homozygous for the R273W mutation, had a partial VWF deficiency (VWF:Ag levels of 0.06 IU/mL and 0.09 IU/mL) and lacked high-molecular weight VWF multimers in plasma. A third patient, also homozygous for the R273W mutation, had a severe VWF deficiency (VWF:Ag level of less than 0.01 IU/mL) and undetectable VWF multimers in plasma. Recombinant VWF having the R273W mutation was expressed in COS-7 cells. Pulse-chase experiments showed that secretion of rVWFR273W was severely impaired compared with wild-type rVWF. However, the mutation did not affect the ability of VWF to form dimers in the endoplasmic reticulum (ER). Multimer analysis showed that rVWFR273W failed to form high-molecular-weight multimers present in wild-type rVWF. We concluded that the R273W mutation is responsible for the quantitative VWF deficiencies and aberrant multimer patterns observed in the affected family members. To identify factors that may function in the intracellular retention of rVWFR273W, we investigated the interactions of VWF expressed in COS-7 cells with molecular chaperones of the ER. The R273W mutation did not affect the ability of VWF to bind to BiP, Grp94, ERp72, calnexin, and calreticulin in COS-7 cells. (Blood. 2000;96:560-568)