PubMed · 10543196
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H Yorifuji. 1999. [Factor XIII].. https://pubmed.ncbi.nlm.nih.gov/10543196/
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OBJECTIVES: The objectives of this study were 1) to assess the importance of an early diagnosis for factor XIII (FXIII) deficiency, and 2) to investigate the molecular basis and mechanism(s) of disease in the patients under study. METHODS: The case histories of 6 FXIII-deficient patients were examined to assess the influence of early versus delayed diagnosis and replacement therapy. The nucleotide sequence of the FXIIIA gene was determined to identify the underlying mutations responsible for the bleeding diathesis in each patient. Molecular modeling was used to predict the mechanism(s) of disease causation for each mutation. RESULTS: All cases presented with umbilical hemorrhage. Patients 1 to 3 were diagnosed, and their prophylactic therapy was commenced in infancy. Diagnosis in patients 4 to 6 was considerably delayed and, as a result, they continued to suffer from many bleeding symptoms. The FXIIIA gene mutations identified in these patients were as follows: a homozygous GAA-->AAA mutation in codon 102 (Glu102Lys) in patient 1 and a homozygous AGC-->AGG mutation in codon 295 (Ser295Arg) in patients 2 to 6. These mutations segregate with disease and are absent from the normal population, suggesting that they are likely to be disease-causing sequence changes. Computer modeling indicates that both the Lys102 and Arg295 mutants are unable to fold correctly, and probably result in unstable FXIIIA molecules. CONCLUSIONS: We demonstrate the importance of recognizing delayed umbilical hemorrhage as a presenting feature for congenital FXIII deficiency, and the value of early diagnosis and prophylaxis. The bleeding disorder of patient 1 was attributable to a homozygous Glu102Lys mutation in FXIIIA. A homozygous Ser295Arg mutation in FXIIIA was responsible for FXIII deficiency in patients 2 to 6.
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Factor XIII is a plasma transglutaminase. Transglutaminases are at least 8 enzymes which cross-link a number of proteins. This type of reaction not only enhances the original functions of substrate proteins, but also adds new functions to them. Factor XIII in plasma is a tetramer (A2B2), and the A subunit contains the active site. Although transglutaminases are homologous, the nucleotide sequences in their 5'-flanking region differ significantly. Accordingly, transcription factors play a major role in the cell type-specific expression of each transglutaminase. A variety of missense and nonsense mutations, and deletions/insertions with or without out-of-frame shift/premature termination and splicing abnormalities have been identified in the genes for A and B subunits in factor XIII deficiency. In some cases, the mRNA level of the A or B subunit was severely reduced. Molecular and cellular bases have also been explored by expression experiments and by molecular modeling. In most cases, impaired folding and/or conformational change of the mutant A or B subunit leads to both intra- and extra-cellular instability, which is responsible for factor XIII deficiency.