title: Congenital afibrinogenemia: intracellular retention of fibrinogen due to a novel W437G mutation in the fibrinogen Bbeta-chain gene.
abstract: Congenital afibrinogenemia is a rare autosomal recessive coagulation disorder characterised by hemorrhagic manifestations of variable entity and by severe plasma fibrinogen deficiency. Among the 31 afibrinogenemia-causing mutations so far reported, only 2 are missense mutations and both are located in the fibrinogen Bbeta-chain gene. Direct sequencing of the fibrinogen gene cluster in two afibrinogenemic Iranian siblings revealed a novel homozygous T>G transversion in exon 8 (nucleotide position 8025) of the fibrinogen Bbeta-chain gene. The resulting W437G missense mutation involves a highly conserved amino acid residue, located in the C-terminal globular D domain. The role of the W437G amino acid substitution on fibrinogen synthesis, folding, and secretion was assessed by in vitro expression experiments in COS-1 cells, followed by qualitative and quantitative analyses of intracellular and secreted mutant fibrinogen. Results of both pulse-chase experiments and enzyme-linked immunosorbent assays demonstrated intracellular retention of the mutant W437G fibrinogen and marked reduction of its secretion. These data, besides elucidating the pathogenetic role of the W437G mutation in afibrinogenemia, underline the importance of the Bbeta-chain D domain in fibrinogen folding and secretion.
authors.affiliation: Department of Biology and Genetics for Medical Sciences, University of Milan, Via Viotti, 3/5 -20133 Milan, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Spena
authors.forename: Rosanna
authors.initials: R
authors.lastname: Asselta
authors.forename: Stefano
authors.initials: S
authors.lastname: Duga
authors.forename: Massimo
authors.initials: M
authors.lastname: Malcovati
authors.forename: Flora
authors.initials: F
authors.lastname: Peyvandi
authors.forename: Pier Mannuccio
authors.initials: PM
authors.lastname: Mannucci
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Tenchini
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D004797:Enzyme-Linked Immunosorbent Assay; D005340:Fibrinogen / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D010375:Pedigree; D017354:Point Mutation; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: C115499:BBeta fibrinogen; D005340:Fibrinogen