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J Clin Pathol. 2017 Feb;70(2):145-153. doi: 10.1136/jclinpath-2016-203862. Epub 2016 Aug 23.

Dysfibrinogenemia-associated novel heterozygous mutation, Shanghai (FGA c.169_180+2 del), leads to N-terminal truncation of fibrinogen Aα chain and impairs fibrin polymerization.

Author information

1
State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
2
Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
3
Department of Laboratory Medicine, Eye and Ear Nose Throat (ENT) Hospital, Shanghai Medical School, Fudan University, Shanghai, China.
4
Faculty of Medical Laboratory Science, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.

Abstract

AIMS:

A novel heterozygous variant, FGA c.169_180+2 del (designated fibrinogen Shanghai), was identified in a patient with dysfibrinogenemia with antiphospholipid antibody syndrome (APS) and recurrent venous thrombosis, and in his asymptomatic father. We aimed to reveal the functional implication of structural change caused by this variant.

METHODS:

Transcription analysis was performed with FGA minigene transfection assay to evaluate the impact of nucleosides deletion on mRNA editing. The fibrinogen isolated from propositus' plasma was used to characterise its functional defects. Fibrin polymerization and clot lysis experiments were performed by optical measurement of turbidity. Thrombin-catalysed fibrinopeptide release was analysed by the reversed-phase, high-performance liquid chromatography. The ultrastructures of fibrin clots were visualised by scanning electron microscopy.

RESULTS:

FGA c.169_180+2 del led to an aberrant mRNA with exon 2 skipping and encoded an shortened Aα chain with 42 amino acids truncation at its N-terminal. The propositus' fibrinogen had an impaired release of fibrinopeptide A and abnormal polymerization with a significantly prolonged lag time, a slower maximum slope and reduced final turbidity. The fibrin clot formed with propositus' fibrinogen showed thicker fibres with looser network structure. Clot lysis was normal using the purified fibrinogen but was significantly impaired using the plasma sample from propositus, compared with that from his father.

CONCLUSIONS:

Fibrinogen Shanghai results in N-terminal truncation of Aα chain, which does not interfere with synthesis, assembly or secretion of fibrinogen, but compromises fibrin polymerization and clot formation. APS at least partially contributes to the development of thrombosis in the propositus.

KEYWORDS:

FIBRINOGEN; GENETICS; HAEMOSTASIS

PMID:
27555433
DOI:
10.1136/jclinpath-2016-203862
[Indexed for MEDLINE]

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