Background: Fibrinogen Matsumoto IV was found in a hypofibrinogenemia caused by a heterozygous missense mutation, i.e., the substitution of the fibrinogen gamma-chain residue Cys153 by Arg.
Methods: To examine the precise basis for the fibrinogen deficiency, mixtures of any two vectors, the fibrinogen Aalpha-, Bbeta-, gamma- (153Cys) or gammam-(153Ala) chain were transfected into Chinese hamster ovary cells (CHO-Aalpha/gamma, -Aalpha/gammam, -Bbeta/gamma, -Bbeta/gammam). Expression and constitution of each of two chains and their complexes in the individual CHO cell lines were identified by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) and immunoblot analysis using polypeptide specific antibodies and two-dimensional electrophoresis (2-DE).
Results: In the CHO-Aalpha/gamma and -Bbeta/gamma, the Aalpha/gamma- or Bbeta/gamma-complex was formed, whereas in the CHO-Aalpha/gammam and -Bbeta/gammam, no Aalpha/gammam- or Bbeta/gammam-complex was observed. These results demonstrate that gamma153Ala cannot assemble with the Aalpha- and Bbeta-chains, leading to impaired fibrinogen assembly and secretion.
Conclusion: gamma153Cys is an essential residue for the fibrinogen assembly which is dependent on Aalpha/gamma- and Bbeta/gamma-complex formation.