Sequensing of exon 28 of Von Willebrand factor in five patients with type 2 Von Willebrand disease

[摘要] English: Von Willebrand disease (VWD) is a common bleeding disorder caused by either quantitative (type1 and 3) or qualitative (type 2) defects of von Willebrand factor (VWF). The diagnosis of VWD usually requires a panel of tests. Several analyses therefore are required to diagnose VWD. These tests are also subjected to pitfalls and it is important to take the pitfalls in to consideration when diagnosing VWD. Despite all these tests, the diagnosis and classification of VWD often remains a challenge. Identification of mutations that cause functional defects of VWF (type 2 VWD) is needed to improve the diagnosis of the disease. Mutations that cause functional abnormalities of VWF occur mostly in exon 28 of the VWF gene. Exon 28 primarily encodes the platelet GPIb and collagen binding domains of VWF (A1 domains) and the ADAMTS13 cleavage domain (A2 domains). Recently, studies in industrialised countries have been conducted on finding mutations on exon 28 but none have been done on South African populations. In this study we searched for mutations in exon 28 of the VWF gene in 5 patients with functional defects of VWF in order to set up the method for genetic analysis of VWD. We used two patients with type 2M, two with type 2B and one with type 2A VWD in this study. The whole exon 28 was analysed in four specific fragments, using PCR with primers that mismatch the pseudogene. The mutations were identified by automatic sequencing of the different fragments. The following polymorphisms were detected. A silent SNP 4641T/C in all five patients, the SNP 4141A/G in three patients, a silent SNP 3795G/A in one patient and a novel silent SNP 4923G/A in another patient. It is important to note that we found a novel SNP in an African patient with type 2B VWD, since no polymorphisms reported in exon 28 were from African populations. Several studies have proven the importance of mutational analysis is solving laboratory diagnosis paradox. The mutations found in the patients with type 2 VWD confirm the diagnosis and validates the importance of molecular diagnosis in VWD. With this study, we have successfully implemented a method to detect mutations in exon 28 of the VWF gene.

[发布机构] University of the Free State