GSE195695
Inspecting VWF gene deep intronic region and in-depth study of the endothelial colony-forming cells to identify an underlying pathogenic molecular mechanism in a type 3 VWD patient
A type 3 von Willebrand disease (VWD) index patient (IP) remains mutation-negative after completion of conventional diagnostic analysis, including multiplex ligation-dependent probe amplification and sequencing of the promotor, exons, and flanking intronic regions of VWF gene (VWF). In this study, we intended to elucidate causitive genetic defect through screening of the whole VWF (including complete intronic region), mRNA analysis, and study of the patient-derived endothelial colony-forming cells (ECFCs). The entire VWF was analyzed by next-generation sequencing (NGS) on an Illumina platform. The NGS revealed a novel variant in VWF intron 8 (997+118 T>G). The subsequent assessments using bioinformatics tools (e.g. SpliceAl) predicted this variant creates a new donor splice site (ss) in intron 8, which could outcompete the consensus 5' donor ss at exon/intron 8 junction. This leads to an aberrant mRNA which contains a premature stop codon, targeting it to nonsense-mediated mRNA decay. The VWF mRNA from whole blood and isolated ECFCs were quantified using the TaqMan assay on an ABI 7500 real-time PCR system. The quantitative analysis confirmed the virtual absence of VWF mRNA. Additionally, the level of secreted VWF from IP ECFCs was considerably reduced (~6% of healthy donors). Overall design: 6 samples