A frameshift mutation in the human fibrinogen Aalpha-chain gene (Aalpha(499)Ala frameshift stop) leading to dysfibrinogen San Giovanni Rotondo.
We have investigated a 53-yr-old asymptomatic white man with decreased functional, but not immunologic, fibrinogen plasma levels together with prolonged thrombin and reptilase times, detected through routine coagulation studies prior to a surgical procedure. A new heterozygous single nucleotide deletion (C) at position Ala499 within the Aalpha-chain gene was identified, which predicted changes of the corresponding amino acids encoded by the subsequent portion of the exon V and the appearance of a premature stop codon at position 518 (Aalpha[499]Ala frameshift stop). The new dysfunctional fibrinogen, San Giovanni Rotondo variant, was confirmed in vivo by SDS-PAGE analysis of HPLC-purified fibrinogen chains. Mass spectrum examination of the abnormal HPLC-purified peak gave an estimated mass (56,088 Da) similar to that predicted by DNA analysis of the mutated Aalpha-chain gene (56,088 Da) and, after tryptic digestion, the truncated Aalpha-chain was shown only in the propositus, who also carried normal Aalpha-chain. In addition, mass spectrum analysis of the tryptic digest of the abnormal chain confirmed the presence of a new and unpaired cysteine at the last position that was predicted to form a disulfide bridge with human serum albumin. Immuno-blot analysis confirmed that fibrinogen San Giovanni Rotondo variant, but not normal fibrinogen. contained substantial amounts of albumin. Present findings confirm that truncated Aalpha-chain lacking part of the terminal domain may be incorporated into mature fibrinogen molecules and normally secreted in the bloodstream.
Margaglione
M
M
Unità di Aterosclerosi e Trombosi, IRCCS Casa Sollievo della Sofferenza, S. Giovanni Rotondo, Italy. ate.tro@operapadrepio.it
Vecchione
G
G
Santacroce
R
R
D'Angelo
F
F
Casetta
B
B
Papa
M L
ML
Grandone
E
E
Di Minno
G
G
D000347:Afibrinogenemia / Q000235:genetics*; D000595:Amino Acid Sequence; D001780:Blood Coagulation Tests; D001797:Blood Protein Electrophoresis; D018389:Codon, Nonsense; D003545:Cysteine / Q000737:chemistry; D004252:DNA Mutational Analysis; D004591:Electrophoresis, Polyacrylamide Gel; D005091:Exons / Q000235:genetics; D015241:Fibrinogens, Abnormal / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D016368:Frameshift Mutation; D006579:Heterozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D017354:Point Mutation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D012709:Serum Albumin / Q000737:chemistry
D018389:Codon, Nonsense; D015241:Fibrinogens, Abnormal; D012709:Serum Albumin; C459442:fibrinogen San Giovanni Rotondo; D003545:Cysteine