Afibrinogenemia: First identification of a splicing mutation in the fibrinogen gamma chain gene leading to a major gamma chain truncation

R. Asselta, S. Duga, T. Simonic, M. Malcovati, E. Santagostino, P. L F Giangrande, P. Mannuccio Mannucci, M. L. Tenchini

Research output: Contribution to journalArticlepeer-review

Abstract

Congenital afibrinogenemia is a rare autosomal recessive disorder characterized by the complete absence of plasma fibrinogen and by a bleeding tendency ranging from mild to moderately severe. Beside a deletion of the almost entire Aα-chain gene, only 2 missense mutations in the C-terminal domain of the Bβ-chain have been very recently described as being associated with afibrinogenemia. We studied a Pakistani patient with unmeasurable plasma levels of functional and immunoreactive fibrinogen. Sequencing of the fibrinogen genes revealed a homozygous G→A transition at position +5 of intron 1 of the γ-chain gene. The predicted mutant fibrinogen γ-chain would contain the signal peptide, followed by a short stretch of aberrant amino acids, preceding a premature stop codon. To demonstrate the causal role of the identified mutation, we prepared expression vectors containing a region of the fibrinogen γ-chain gene spanning from exon 1 to intron 4 and carrying either a G or an A at position +5 of intron 1. Transient transfection of the mutated plasmid in HeLa cells, followed by RNA extraction and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, allowed us to demonstrate the production of an erroneously spliced messenger RNA (mRNA), retaining intron 1, as shown by direct sequencing. A normal splicing occurred in HeLa cells transfected with the wild-type plasmid. This is the first report of a mutation in the fibrinogen γ-chain gene causing afibrinogenemia and indicates that, in addition to the Aα and Bβ-chain genes, the γ-chain gene must also be considered in mutation screening for afibrinogenemia. (C) 2000 by The American Society of Hematology.

Original languageEnglish
Pages (from-to)2496-2500
Number of pages5
JournalBlood
Volume96
Issue number7
Publication statusPublished - Oct 1 2000

ASJC Scopus subject areas

  • Hematology

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