Coagulation factor VA2440G causes east Texas bleeding disorder via TFPIα
Lisa M. Vincent, … , Dianna M. Milewicz, Björn Dahlbäck
Lisa M. Vincent, … , Dianna M. Milewicz, Björn Dahlbäck
Published August 27, 2013
Citation Information: J Clin Invest. 2013;123(9):3777-3787. https://doi.org/10.1172/JCI69091.
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Research Article

Coagulation factor VA2440G causes east Texas bleeding disorder via TFPIα

Abstract

The autosomal dominantly inherited east Texas bleeding disorder is linked to an A2440G variant in exon 13 of the F5 gene. Affected individuals have normal levels of coagulation factor V (FV) activity, but demonstrate inhibition of global coagulation tests. We demonstrated that the A2440G mutation causes upregulation of an alternatively spliced F5 transcript that results in an in-frame deletion of 702 amino acids of the large activation fragment, the B domain. The approximately 250-kDa FV isoform (FV-short), which can be fully activated by thrombin, is present in all A2440G carriers’ plasma (n = 16). FV-short inhibits coagulation through an indirect mechanism by forming a complex with tissue factor pathway inhibitor-α (TFPIα), resulting in an approximately 10-fold increase in plasma TFPIα, suggesting that the TFPIα:FV-short complexes are retained in circulation. The TFPIα:FV-short complexes efficiently inhibit thrombin generation of both intrinsic and extrinsic coagulation pathways. These data demonstrate that the east Texas bleeding disorder–associated F5A2440G leads to the formation of the TFPIα:FV-short complex, which inhibits activation and propagation of coagulation.

Authors

Lisa M. Vincent, Sinh Tran, Ruzica Livaja, Tracy A. Bensend, Dianna M. Milewicz, Björn Dahlbäck

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Figure 9

Normalization of thrombin generation in affected plasma by anti-TFPI and effects of adding TFPIα to unaffected plasma.

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Normalization of thrombin generation in affected plasma by anti-TFPI and...
(A) Polyclonal antibodies against TFPI (40 μl; final concentration of 100 μg/ml) or 40 μl HNBSA buffer control were mixed with 40 μl pooled plasma from affected or unaffected family members, and after 5 minutes incubation at 37°C, the TGA was started by addition of substrate (20 μl) and TF/PL/Ca2+ mixture (20 μl). (B) Increasing concentrations of rTFPIα (in 8 μl) were added to unaffected plasma (72 μl), yielding the indicated final concentrations, and tested in the TGA. A dose-dependent prolongation of the lag phase was observed, the highest TFPI concentration also decreasing the thrombin peak.