The results of the study show that this promoter deletion significantly reduces transcriptional activity in vitro in endothelial and liver cells and in vivo in a mouse model. mutation. These studies show that this 13-bp deletion mutation alters the binding of Ets (and possibly GATA) proteins to theVWFpromoter and significantly reducesVWFexpression, thus playing a central pathogenic role in the type 1 von Willebrand disease phenotype in the index case. == Introduction == von Willebrand factor (VWF) is a multimeric adhesive glycoprotein that plays several key roles in hemostasis. It HPGDS inhibitor 2 mediates platelet adhesion and aggregation at the sites of vascular injury, and acts as a carrier for coagulation factor VIII to protect it from proteolytic degradation.1,2VWF plasma levels below 50% are found in the most common type of von Willebrand disease (VWD), type 1 VWD, which is characterized by a moderate/moderate deficiency of functionally normal VWF. The understanding of the genetic basis and molecular pathophysiology of type HPGDS inhibitor 2 1 VWD has been a challenge, and a heterogeneous array ofVWFgene mutations, located throughout the gene, have been documented in these patients. The details of these mutations are outlined and updated around the ISTH VWF SSC Database (http://www.sheffield.ac.uk/VWF/index.html). Three large population studies of type 1 VWD patients have detailed the spectrum ofVWFgene mutations in HPGDS inhibitor 2 several European Countries and in Canada. However, candidate pathogenicVWFmutations were not found in 27%,3in 36%,4and in 28%5of index cases diagnosed with type 1 VWD. In the Canadian study, 8 sequence variations within the 5 regulatory region of theVWFgene were found after sequencing DNA from 123 index cases with type 1 VWD. These 5 regulatory sequence changes represented 16% of the total candidate mutations found in this study. However, to date, there has been no functional evidence to support the pathogenic nature of any of these sequence variations. EarlierVWFpromoter studies have indicated that, in vitro, the basal transcription of the humanVWFgene is usually mediated through a region in the promoter located between base pairs 89 and +19 (relative to transcription start site, TSS +1). This region was functional in both endothelial and nonendothelial cell types.6In vivo studies exhibited that VWF sequences between 487 to +247 are responsible for promoter activation in brain vascular endothelial cells.7 The 60/+19 region has been shown to be a critical area within theVWFgene promoter, possessing 2 Ets-binding motifs, with the HPGDS inhibitor 2 5-most motif being more critical to transcriptional activation.6In transgenic mice, a larger VWF fragment (2182 bp) containing the 5-flanking sequences and including exon 1 and intron 1 of the gene has been shown to activate transgene expression Rabbit polyclonal to PAI-3 in endothelial cells of the heart, skeletal muscles, and brain,8suggesting that additional distantVWFgene sequences are required for expression in other vascular endothelial cells in vivo. Specific interaction between positive and negative regulatory sequences together with their transcription factors have been recognized HPGDS inhibitor 2 within this region and have contributed to the endothelial-specificVWFmRNA expression levels.6,9,10,11The local vascular microenvironment also appears to contribute to the regulation of endothelial VWF expression,8and it is well recognized that there is considerable heterogeneity in the distribution and nature of endothelial VWF expression throughout the vasculature.12 Despite some progress in the past 2 decades with respect to the mechanisms that regulate endothelial expression of VWF, many details of this process remain unresolved. Natural transcriptional mutants resulting in the quantitative trait, type 1 VWD, provide an opportunity to add new knowledge in this area. In this study, we provide details of the functional characterization of a 13-bp deletion within the basal promoter of the VWF gene. We document evidence using both in vitro and in vivo experimental methods that this deletion reduces transcriptional activation of theVWFregulatory region. Overall, these results provide strong evidence that this promoter deletion plays a key pathogenic role in the type 1 VWD phenotype in this patient. == Methods == == Confirmation of the c.-1522_-1510del13 mutant, patient phenotype, and screening of normal population == This mutation was.