Amino Acid Substitution; Hemorrhagic Disorders/etiology; Mutation, Missense; Platelet Aggregation/genetics; Platelet Glycoprotein GPIIb-IIIa Complex/antagonists & inhibitors; Point Mutation; von Willebrand Disease, Type 2/genetics; von Willebrand Factor/genetics; Adenosine Triphosphate/metabolism; Animals; Blood Platelets/metabolism; Calcium Signaling/physiology; Hemorrhagic Disorders/physiopathology; Humans; Intracellular Signaling Peptides and Proteins/physiology; Male; Mice; Mice, Inbred C57BL; Phospholipase C gamma/physiology; Phosphorylation; Platelet Glycoprotein GPIIb-IIIa Complex/physiology; Protein Processing, Post-Translational; Protein-Tyrosine Kinases/physiology; Receptors, Collagen/physiology; Recombinant Fusion Proteins/metabolism; Syk Kinase; rap1 GTP-Binding Proteins/metabolism; von Willebrand Disease, Type 2/blood; von Willebrand Factor/physiology