A novel fibrinogen gamma-chain mutation, p.Cys165Arg, causes disruption of the gamma 165Cys-B beta 227Cys disulfide bond and ultimately leads to hypofibrinogenemia

作者：Zhou, WeiJie; Luo, Meiling; Yan, Jie; Xiang, Liqun; Wei, Aiqiu; Deng, Xuelian; Liao, Lin; Cheng, Peng; Deng, Donghong; Lin, Faquan^*

来源：Thrombosis Research, 2018, 172: 128-134.

DOI：10.1016/j.thromres.2018.10.018

• Congenital hypofibrinogenemia
• Fibrinogen
• Mutations
• Disulfide bond
• Thromboelastogram

Background: Congenital hypofibrinogenemia is a type of hereditary disease characterized by impaired fibrinogen synthesis and/or secretion induced by mutations in the fibrinogen gene. Objectives: We investigated the phenotypes, genotypes, and pathogenesis of congenital hypofibrinogenemia in an affected family.
Patients/methods: The proband had a risk of bleeding; therefore, conventional coagulation screening was performed for the proband and her family members. Mutation sites in all exons and flanking sequences of FGA, FGB, and FGG were identified, with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) performed to indicate the expression of abnormal chains. The effect of the mutation sites on fibrinogen structure and function was predicted by molecular modeling, and purified plasma fibrinogen from the proband was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and scanning electron microscopy. Thromboelastography was applied to assess the risk of bleeding and clotting in the proband.
Results: Fibrinogen levels in the proband were 1.21 g/L, 1.31 g/L, and 1.38 g/L according to Clauss assay, the prothrombin time method, and enzyme-linked immunosorbent assay, respectively. A novel heterozygous mutation (gamma Cys165Arg), a heterozygous mutation (AaIle6Val), and two genetic polymorphisms (A alpha Thr331Ala and B beta Arg478Lys) in fibrinogen were found in the proband, and MALDI-TOF MS indicated absence of the mutated chain in patient plasma. Additionally, the heterozygous mutation (gamma Cys165Arg) displayed substitution of a nonpolar. gamma 65Cys (low mass) with a positively charged Arg (high mass) along with a small fiber diameter and loose network structure.
Conclusions: Fibrinogen gamma Cys165Arg mutations cause damage to the interchain disulfide bonds of fibrinogen and hinder fibrinogen secretion, possibly explaining the pathological mechanism associated with congenital hypofibrinogenemia.

• 出版日期2018-12
• 单位广西医科大学