Collagen-induced in vitro thrombosis. Whole blood was perfused for 5 minutes over an immobilized collagen surface at 1500 s⁻¹. The adhesion of DiOC₆-labeled platelets was recorded. (A) Views of platelet adhesion at different times (30 seconds, 1 minute, 2 minutes, and 5 minutes) of 1 out of 6 significant experiments from VavCre/JAK2^V617F (KI) and WT mice are shown. Original magnification ×20 for all panels. Quantification of the covered surface obtained with VavCre/JAK2^V617F platelets (KI, n = 6) and of SCLCreER^t/JAK2^V617F platelets (TM, n = 4 per group) and their matched controls is shown in panels B and C, respectively. **P < .007. (D) Mosaic views of SCLCreER^t/JAK2^V617F (TM) platelets and their controls (VH) are shown at day 6 (D6) and day 60 (D60).