Tail bleeding time assays.

Shown are the times obtained for individual GP Ibα^−/−(mouse Bernard-Soulier syndrome) and Tg³³(Tg³³; GP Ibα^null) animals. Normal mouse bleeding times range from 1 to 3 minutes.11 Mice lacking the extracytoplasmic domain of GP Ibα have a severe bleeding phenotype even with an amelioration of the macrothrombocytopenia. These results support the in vivo relevance of the extracytoplasmic GP Ibα ligand-binding domain in normal hemostasis.