A novel fibrinogen variant (fibrinogen Seoul II; AαGln328Pro) characterized by impaired fibrin α-chain cross-linking

Abstract

We report a novel fibrinogen variant (fibrinogen Seoul II), which has a heterozygous point mutation from CAA to CCA leading to AαGln328Pro. The mutation site is among several glutamine residues that serve as α-chain cross-linking acceptor sites. Fibrinogen Seoul II was found in a 51-year-old male patient and his family in Seoul, Korea. The patient was diagnosed with myocardial infarction at age 43. Eight years later he was admitted to the emergency room due to recurrence of the disease, where he expired under treatment with tissue plasminogen activator (t-PA). Fibrin polymerization curves, made using purified fibrinogen from the patient's relatives, showed a decreased final turbidity, suggesting Seoul II fibrin clots are composed of thinner fibers. This supposition was verified using scanning electron microscopy. Alpha-polymer formation by the mutant fibrinogen upon thrombin treatment in the presence of factor XIII and calcium was distinctly impaired. This result confirms that the residue Aα328 plays a pivotal role in α-chain cross-linking.