Genomics of Fibrin Clot Structure in Patients With Constitutional Dysfibrinogenemia

Hereditary dysfibrinogenemia results from monoallelic mutation in one of the fibrinogen genes (FGA, FGB, FGG). The spectrum of molecular abnormalities is broad, leading to several subtypes of coagulation disorders with specific biological and clinical features. The correlation between the genotype and the phenotype is poor, and the clinical course of patients, from major bleeding to recurrent thromboses, is unpredictable. Fibrin clot structure is a determinant of the risk of thrombosis in cardiovascular diseases. In all individuals, fibrin networks define the propensity of clot to be more resistant to removal or, on the contrary, susceptible to fragmentation leading to bleeding complications. Besides fibrinogen variants, other relatively common genetic polymorphisms in coagulation and fibrinolytic pathways may affect the fibrin clot structure and therefore act as modifiers of the blood clot function.

In this proposal, the investigators will analyze properties (polymerization, fibrinolysis, viscoelastic properties, permeation) and ultrastructure (size, number, packaging, architecture of fibrin fiber by confocal microscopy and scanning electron microscopy) of plasma-based clots in relation to the presence of genetic modifiers (polymorphisms). Polymorphisms will be detected using a whole exome sequencing (WES) in a selected panel of genes of the coagulation and fibrinolytic pathways. The gene panel of 28 genes will include the three fibrinogen genes plus 25 potential modifier genes including F5, F2, PAI-1, PROCR and MTHFR. The overall clot phenotype will be correlated to the presence of prothrombotic polymorphisms and to the patient's clinical phenotype. The investigators plan to include about 100 patients with dysfibrinogenemia. The combination of integrative hemostasis models with genetic dataset will provide a global view of the patient's individual hemostatic profile. This may allow to better predict the clinical outcome and help provide a more personalized therapeutic strategy and precision medicine. In addition, the development of models allowing a reliable global assessment of fibrin clot architecture will be the basis for further research in other acquired diseases involving thrombotic or bleeding events.