Molecular characterization of 3 factor V mutations, R2174L, V1813M, and a 5-bp deletion, that cause factor V deficiency

Abstract

We identified 3 mutations in the factor V (FV) gene (F5) associated with FV deficiency in 3 unrelated Japanese patients. Patient 1 had severe bleeding symptoms (plasma FV activity, <1%; FV antigen, 9%) and was a compound heterozygote for a novel 5-bp deletion in exon 22 and the V1813M mutation. Patient 2 had moderate bleeding symptoms (plasma FV activity, <1%; FV antigen, 4%) and was homozygous for the V1813M mutation. Patient 3 had very mild symptoms (plasma FV activity, 1%; FV antigen, 5%) and was homozygous for the novel R2174L mutation. A study of recombinant protein expression revealed that the FV coagulant-specific activities in conditioned media for the FV-R2174L and FV-V1813M mutants were reduced to approximately 40% and 28% of wild-type FV, respectively. The amounts of FV-R2174L protein and messenger RNA in the platelets of patient 3 were similar to those of healthy subjects; however, the amount of FV-V1813M protein in patient 2 was decreased. Our data suggest that the severity of the bleeding tendency in patients with FV deficiency is correlated not only with plasma FV activity but also with the amount of FV protein in the platelets.

Identification of four novel mutations in F5 associated with congenital factor V deficiency

“…Along these lines, a study on transgenic mice expressing the Fv minigene revealed that FV-deficient mice, that die either during embryonic development or at birth from massive hemorrhaging, could be rescued by a very low level (\0.1%) of FV expression [15]. Alternatively, FV stored in platelets may have contributed to local hemostasis [16,17]. Approximately, 80% of FV is located in the plasma, and the remaining 20% is contained within platelet a-granules [5].…”

Residual platelet factor V ensures thrombin generation in patients with severe congenital factor V deficiency and mild bleeding symptoms

“…Despite this important observation, platelet FV is not routinely evaluated in FV-deficient patients and only 3 other studies report platelet FV levels in patients with severe FV deficiency. [32][33][34] No platelet FV antigen or activity could be demonstrated in 2 patients with undetectable plasma FV. 32,33 In another FV-deficient patient, platelet FV could be visualized by Western blotting, but its activity was not determined.…”

“…32,33 In another FV-deficient patient, platelet FV could be visualized by Western blotting, but its activity was not determined. 34 To get more insight into the role of platelet FV in FV deficiency, we have measured thrombin generation and platelet FV levels in 4 patients with severe congenital FV deficiency.…”

Novel FV mutation (W1920R, FVNara) associated with serious deep vein thrombosis and more potent APC resistance relative to FVLeiden

“…25 The WT and mutant plasmids used in transfection experiments were purified. Vectors expressing recombinant proteins were transfected into HEK293 cells, using the lipofection method.…”