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 3

Analysis of the expression of FV-short alternative splicing variant in affected patients.

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Analysis of the expression of FV-short alternative splicing variant in a...
(A) Transcript-specific reverse transcription of 1 μg of RNA was completed using Superscript II RNase H- Reverse Transcriptase and FVShortR primer. cDNA was PCR amplified using Ex Taq Polymerase and FVShortF and FVShortR primers. Lane 1: unaffected liver RNA RT-PCR; lane 2: normal peripheral leukocyte RNA; lanes 3–5: unaffected patient RNA RT-PCR; lanes 6–8: affected patient RNA RT-PCR. The lanes were run on the same gel but were noncontiguous. (B) Quantitative real-time PCR of FV-short transcript was completed using a custom TaqMan assay. Fold difference of FV-short expression in unaffected controls (n = 3) compared with affected patients (n = 3). Fold differences are normalized to 18S expression and relative to corresponding target expression in normal peripheral leukocyte RNA. The 1-tailed P value calculated using the Student’s t test was 0.02.