Grant: Operating Grant

von Willebrand factor (VWF) is a large adhesive pro-coagulant protein that is required for two key functions in normal blood clotting: the initial attachment of blood platelets to sites of blood vessel damage, and the carriage of clotting factor VIII in blood. Inherited quantitative or qualitative abnormalities of VWF result in the inherited bleeding disorder, von Willebrand disease (VWD). The aim of these studies is to investigate how changes to the amount and function of VWF affect blood clotting. The first group of studies will characterize genetic sequences involved in regulating how much VWF is made within the body. These studies will initially be based upon results obtained in the investigation of a large population of patients with low blood levels of VWF. Abnormalities to the genetic control sequences documented in these patients will be investigated for their functional significance. In the later stages of the project, we will also begin to evaluate the influence of more distant sequences on VWF gene expression. In the second and third aims of this project, we will investigate the effects of qualitative changes to the VWF protein that result in abnormal blood clotting. Variant forms of the protein that show altered cleavage by the processing enzyme ADAMTS13 and abnormal binding to platelets will be assessed though a variety of in vitro and in vivo approaches. Initial studies will confirm the functional deficits of these variant proteins through standard in vitro analysis. Subsequently, recombinant forms of the variant proteins will be infused into mice with severe VWF deficiency to assess their recovery and circulation times. Finally, in vivo analysis of these variant forms of VWF will be evaluated following delivery of mutant transgenes through a hydrodynamic injection approach. These in vivo studies will involve a comprehensive series of investigations to determine the influence of these VWF protein changes on normal blood clotting.