FV and FVIII levels in Lman1 WT (+/+), heterozygote (+/−), and homozygous (−/−) mice. (A) Comparison of FVIII activities between WT and Lman1^−/− mice. FVIII activity was determined at ∼ 6 months of age by a 2-stage chromogenic assay. (B) Variation in FV activity for individual mice over a 6-week period. Blood was collected from each individual mouse at 2-week intervals, beginning at ∼ 6 months of age. FV activity was determined by a one-stage clotting assay. The group averages of each time points were plotted, with the 6-week average of FV levels in WT mice designated as 100%. (C) Relative FV antigen (%) in plasma (equal volume) and in platelets (equal number) as determined by Western blot analysis. The β-actin level in platelets serves as a loading control. The relative levels in different individual mice at ∼ 6 months of age were quantified and normalized against β-actin. Vertical bars in all panels represent SD.