Identification of a candidate missense mutation in a family with von Willebrand disease type IIC

Abstract

A screening project to identify candidate molecular defects causing von Willebrand disease type IIC (VWD IIC) in a German family was carried out using polymerase chain reaction (PCR) amplification of all 52 exons of the von Willebrand factor (VWF) gene, subsequent electrophoresis of single and double stranded DNA and direct sequencing of PCR products with aberrant electrophoretic patterns. Only one candidate mutation, G550R, caused by a G-->A transition, was detected in exon 14 of the pro-VWF gene sequence. This mutation was not found on 200 chromosomes of normal individuals. The propositus was homozygous for the mutation and for an extended intragenic haplotype, composed of eight polymorphic markers. Further family members were heterozygous for the mutation and were phenotypically normal or only mildly affected, in accordance with the recessive pattern of inheritance for VWD type IIC. The mutation could influence one of the presumed active centers for the suspected multimerizing enzymatic activity of pro-VWF localized in the D1 and D2 domain, which corresponds to exon 5 and exon 14 of the VWF gene.

The role of the D1 domain of the von Willebrand factor propeptide in multimerization of VWF

“…28 In patients with a heterozygous abnormality, the functional wild-type VWFpp is involved in multimerization of the wild-type VWF molecules and is unavailable to function in trans. Naturally occurring mutations in the VWFpp (Tyr87Ser [this study], Arg273Trp, 29 Asn528Ser, 30 Gly550Arg, 31 Cys623Trp, 25 and 625insGly 25 ) all demonstrate altered multimerization, presumably resulting from their VWFpp defects, yet none are located in close proximity to any functional areas. An intact VWFpp appears to be prerequisite for the N-terminal multimerization of VWF in the trans Golgi network (TGN).…”

The mutation N528S in the von Willebrand factor (VWF) propeptide causes defective multimerization and storage of VWF

“…These parameters are indicative of the historic subclassification of type 2A, subtype IIC. [28][29][30][31] These patients are likely to have a VWFpp mutation. 13,[29][30][31][32] It is not surprising that VWFpp mutations are associated with VWF multimerization abnormalities, as VWFpp has been shown to play a critical role in facilitating VWF multimerization.…”

“…[28][29][30][31] These patients are likely to have a VWFpp mutation. 13,[29][30][31][32] It is not surprising that VWFpp mutations are associated with VWF multimerization abnormalities, as VWFpp has been shown to play a critical role in facilitating VWF multimerization. 33 An unexpected finding from the current study is the defective VWF-regulated storage in affected patients.…”

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

“…In (16,17), an aminoterminal domain cleaved from the mature vWF subunit during the course of posttranslational processing and thought to be necessary for normal multimer assembly (18)(19)(20) (37). The plasmid pJB10 was used to produce the recombinant virus and contained the following elements in a 5' to 3' direction: (i) a consensus ribosomal binding site; (ii) the initiating vWF Met codon, ATG, and the remainder of the vWF signal peptide sequence; (iii) coding sequence for the first 3 amino acid residues of the vWF propeptide; and (iv) coding sequence for mature vWF residues Glu1366 to Lys2050 and the translation termination codon, TGA (38).…”