Homozygous and heterozygous deletions of the von Willebrand factor gene in patients and carriers of severe von Willebrand disease.

Abstract

Severe von Willebrand disease is characterized by undetectable or trace quantities of von Willebrand factor in plasma and tissue stores. We have studied the genomic DNA of 10 affected individuals from six families with this disorder using probes from the 5' and 3' ends of the vWF cDNA and with a probe extending from the 5' end into the central region. Southern blots of restriction endonuclease digests and gene dosage analysis measurements carried out with quantitative slot blots of undigested genomic DNA separated these patients into three groups. The first group consisted of a family with complete homozygous deletions of the vWF gene in the four probands. Gene dosage analysis was consistent with heterozygous deletions in both of the asymptomatic parents and four asymptomatic siblings of this kindred (P less than 0.01). The second group was comprised of a family in which there was a complete heterozygous deletion of the vWF gene in the proband and one asymptomatic parent, suggesting that a different type of genetic abnormality was inherited from the other parent. Thus, the patient appeared to be doubly heterozygous for interacting genetic abnormalities affecting vWF expression. In the third group, no gene deletions could be detected. Alloantibodies developed only in the kindred with homozygous deletions. These techniques should prove useful in identifying carriers of severe von Willebrand disease and also in defining patients predictably at risk of developing alloantibodies to vWF.

Molecular characterization, recombinant protein expression, and mRNA analysis of type 3 von Willebrand disease: Studies of an Italian cohort of 10 patients

“…HRM analysis was then carried out for 25 exons (number 4,6,8,9,11,12,16,17,19,20,21,23,25,30,34,35,36,38,39,40,41,44,46,48,51) in all patients. This is a mutation scanning technique that monitors the progressive change in fluorescence caused by the release of an intercalating DNA dye from a DNA duplex as it is denatured with marginal increases in temperature [18].…”

“…VWD3 patients may develop alloantibodies against VWF as a consequence of their treatment with VWF/FVIII concentrates. Since this complication renders replacement therapy ineffective and may also be the cause of life threatening anaphylactic reactions, screening for homozygous large deletions, associated previously with the presence of alloantibodies [5][6][7][8] is highly recommended. Of late, we have reported a retrospective studies on the management of inherited VWD in Italy that included 66 VWD3 patients.…”

von Willebrand disease: advances in pathogenetic understanding, diagnosis, and therapy

“…21 The Ͼ 110 type 3 VWD cases that have been genetically characterized show a range of VWF mutations, from large VWF deletions through a miscellany of null mutations to missense mutations that prevent VWF biosynthesis and secretion. Although initial studies of the infrequent cases of type 3 VWD developing alloantibodies to VWF showed an association with VWF deletion mutations, 22,23 there has been no systematic confirmation of this observation. 24 Type 1 VWD Type 1 disease comprises 65% to 75% of VWD cases in most series.…”

“…The VWF gene sequence is replicated in part by a partial VWF pseudogene on chromosome 22. This evolutionary remnant recapitulates exons 23-34 of the VWF gene with 3% variance, a fact that significantly complicates the genetic analysis of this central region of the VWF gene.…”

The molecular defect in type IIB von Willebrand disease. Identification of four potential missense mutations within the putative GpIb binding domain.

“…Large gene deletions appear to be an uncommon mechanism for vWD, seen primarily in patients with inhibitors to vWF (14,24,25). Missense mutations within the vWF A2 domain were recently identified in two patients with Type IIA vWD (26) and additional Type 11A patients may demonstrate other mutations in the same region (27).…”