Fibrinogen Lincoln: a new truncated alpha chain variant with delayed clotting.
A patient referred for preoperative investigation of prolonged bleeding and easy bruising was found to have increased thrombin and reptilase times; however, the thrombin catalysed release of fibrinopeptides A and B was normal. Analysis of five other family members, spanning three generations, indicated that three had a similar defect and suggested autosomal dominant inheritance. Non-reducing SDS-PAGE of purified fibrinogen from affected individuals showed that the 340 kD form of their fibrinogen ran as a doublet. SSCP (single-stranded conformational polymorphism) analysis of exon 5 of the A alpha gene, which encodes the C-terminal half of the chain, confirmed the presence of a mutation. Cycle sequencing of PCR amplified DNA revealed a 13 base pair deletion (nt 4758-4770), resulting in a frame-shift at Ala 475, which translates as four new amino acids before terminating at a new stop codon (-476His-Cys-Leu-Ala-Stop). The presence of a circulating truncated A alpha chain was confirmed when SDS-PAGE gels were probed with an alpha chain specific antisera; which showed that the variant A alpha chain comigrated with gamma chains. The truncation results in a variant A alpha chain with a deletion of 131 amino acids (480-610), and four new amino acids at the C-terminal.
Ridgway
H J
HJ
Molecular Pathology Laboratory, Christchurch Hospital, New Zealand.
Brennan
S O
SO
Gibbons
S
S
George
P M
PM
D000328:Adult; D001483:Base Sequence; D001778:Blood Coagulation Disorders / Q000151:congenital* / Q000235:genetics*; D017931:DNA Primers / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005340:Fibrinogen / Q000235:genetics*; D016368:Frameshift Mutation; D017353:Gene Deletion; D006801:Humans; D015151:Immunoblotting; D008969:Molecular Sequence Data; D010375:Pedigree; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D017422:Sequence Analysis, DNA
D017931:DNA Primers; D005340:Fibrinogen