Identification of eight novel coagulation factor XIII subunit A mutations: implied consequences for structure and function

Abstract

BackgroundSevere hereditary coagulation factor XIII deficiency is a rare homozygous bleeding disorder affecting one person in every two million individuals. In contrast, heterozygous factor XIII deficiency is more common, but usually not associated with severe hemorrhage such as intracranial bleeding or hemarthrosis. In most cases, the disease is caused by F13A gene mutations. Causative mutations associated with the F13B gene are rarer. Design and MethodsWe analyzed ten index patients and three relatives for factor XIII activity using a photometric assay and sequenced their F13A and F13B genes. Additionally, structural analysis of the wildtype protein structure from a previously reported X-ray crystallographic model identified potential structural and functional effects of the missense mutations. ResultsAll individuals except one were heterozygous for factor XIIIA mutations (average factor XIII activity 51%), while the remaining homozygous individual was found to have severe factor XIII deficiency (<5% of normal factor XIII activity). Eight of the 12 heterozygous patients exhibited a bleeding tendency upon provocation. ConclusionsThe identified missense (Pro289Arg, Arg611His, Asp668Gly) and nonsense (Gly390X, Trp664X) mutations are causative for factor XIII deficiency. A Gly592Ser variant identified in three unrelated index patients, as well as in 200 healthy controls (minor allele frequency 0.005), and two further Tyr167Cys and Arg540Gln variants, represent possible candidates for rare F13A gene polymorphisms since they apparently do not have a significant influence on the structure of the factor XIIIA protein. Future in vitro expression studies of the factor XIII mutations are required to confirm their pathological mechanisms.Key words: factor XIII deficiency, FXIII-A, FXIII-B, structural analysis. Citation: Ivaskevicius V, Biswas

Impaired dimer assembly and decreased stability of naturally recurring R260C mutant A subunit for coagulation factor XIII

“…A number of mutations in the gene for FXIII-A have been identified in patients with its deficiency (12,13,18,32). These natural mutations are highly heterogeneous.…”

“…The FXIII-A cDNA encodes a mature protein of 731 amino acids, including an activation peptide of 37 residues at the amino-terminus and a catalytic Cys314 residue (11). To date, $100 mutations in the gene for FXIII-A have been identified in patients with FXIII-A deficiency (http://www.f13-database.de) (12,13). These mutations are highly heterogeneous and include a variety of nonsense and missense mutations, deletions and insertions with or without frame-shift/premature termination, splicing abnormalities, etc.…”

Novel aspects of factor XIII deficiency

“…This finding suggests that the C-terminal part of b-barrel 2 is essential for the expression of FXIII activity. Ivaskevicius et al [19 ] also described a novel homozygous mutation resulting in a stop codon in the same area of b-barrel 2 (c.1994G>A; p.Trp664X). Unfortunately, in this case, FXIII antigen level was not reported and the subtype of deficiency could not be established.…”

Mild factor XIII deficiency and concurrent hypofibrinogenemia

“…The frequency of mild congenital FXIII deficiency is unknown [5]. FXIII is the last enzyme to be activated in the blood coagulation pathway and functions to cross-link a and g-fibrin chains, strengthening the clot, and increasing resistance to fibrinolysis [6].…”