Whole blood isolated from Fib^AEK mice does not clot following the addition of thrombin or thromboplastin but supports platelet aggregation similar to WT fibrinogen. Clotting times for whole blood from each of 5 WT and Fib^AEK mice were determined following the addition of 2 U/mL (A) thrombin or (B) thromboplastin. The horizontal bars indicate average clotting times (seconds) for the groups. Note that clots were never detected for whole blood isolated from Fib^AEK mice following the addition of thrombin or thromboplastin. P < .001 by Fisher’s exact test for each analysis. (C) Qualitative analysis of whole blood clots and clot retraction following the addition of thromboplastin. Retracted clots were readily observed within 30 minutes for samples of whole blood isolated from WT mice; whereas even up to 18 hours following addition of thromboplastin, no clot of any form could be appreciated in whole blood samples isolated from Fib^AEK mice. (D) Platelet aggregation analysis using platelet-rich plasma isolated from WT, Fib^−/−, and Fib^AEK mice. For each analysis, aggregation was initiated using the platelet agonist ADP.