Characterisation of a novel thrombomodulin c.1487delC,p.(Pro496Argfs*10) variant and evaluation of therapeutic strategies to manage the rare bleeding phenotype.

Morrow, Gael B.; Beavis, James; Harper, Sarah; Bignell, Patricia; Laffan, Mike A.; Curry, Nicola

Abstract

A novel variant in the thrombomodulin (TM) gene, c.1487delC,p.(Pro496Argfs*10), referred to as Pro496Argfs*10, was identified in a family with an unexplained bleeding disorder. The Pro496Argfs*10 variant results in loss of the transmembrane and intracellular segments of TM and is associated with an increase in soluble TM (sTM) in the plasma. The aim of this study was to characterise the effect of elevated sTM on thrombin generation (TG) and fibrinolysis, and to evaluate therapeutic strategies to manage the patients. Plasma samples were obtained from two patients carrying the variant. TG was triggered using 5 pM tissue factor and measured using the Calibrated Automated Thrombogram. A turbidity clot lysis assay was used to monitor fibrinolysis. TM antigen was quantified by ELISA. Patients with the Pro496Argfs*10 variant had significantly elevated plasma sTM compared to controls (372.6 vs. 6.0 ng/ml). TG potential was significantly lower in patients but was restored by inhibition of activated protein C (APC) or addition of activated Factor VII (FVIIa) or platelet concentrates. In vitro experiments suggested that activated prothrombin complex concentrates (APCC) posed a risk of thrombosis. The time to 50% lysis was significantly prolonged in patients compared to controls, 69.7 vs. 42.3 min. Clot lysis time was shortened by inhibition of activated thrombin activatable fibrinolysis inhibitor (TAFIa). Our data demonstrate that increased sTM enhances APC generation and reduces TG. Simultaneously, the rate of fibrinolysis is delayed due to increased TAFI activation by sTM. Treatment with platelet or FVIIa concentrates may be beneficial to manage this rare bleeding disorder.

Citation

MORROW, G.B., BEAVIS, J., HARPER, S., BIGNELL, P., LAFFAN, M.A. and CURRY, N. 2021. Characterisation of a novel thrombomodulin c.1487delC,p.(Pro496Argfs*10) variant and evaluation of therapeutic strategies to manage the rare bleeding phenotype. Thrombosis research [online], 197, pages 100-108. Available from: https://doi.org/10.1016/j.thromres.2020.11.002

• Journal Article Type: Article
• Acceptance Date: Nov 1, 2020
• Online Publication Date: Nov 9, 2020
• Publication Date: Jan 31, 2021
• Deposit Date: Aug 7, 2023
• Journal: Thrombosis research
• Print ISSN: 0049-3848
• Electronic ISSN: 1879-2472
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 197
• Pages: 100-108
• DOI: https://doi.org/10.1016/j.thromres.2020.11.002
• Keywords: Blood platelets; Factor V; Protein C; Thrombin; Thrombomodulin
• Public URL: https://rgu-repository.worktribe.com/output/2034934