Analyses on Mechanisms for Biosynthesis and Release of Human Coagulation Factor XIII at Molecular, Cellular, and Individual Levels

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Expression of XIIIA in human cell lines decreased during cell proliferation and increased in an apparent steady state of cell growth. During cell passage, XIIIA gradually decreased in U937 cells, in contrast, it increased in MEG-01 cells. Immunofluorescence microscopy revealed three typical localization patterns of XIIIA in MEG-01 cells; (1) a diffuse pattern in cytoplasm; (2) a filamentous structure around the nucleus; and (3) a diffuse pattern in the nucleus. Nuclear localization of XIIIA was also found in PMA-treated THP-1 cells. XIIIA partly co-localized with an intermediate filament protein vimentin, and the direct interaction between XIIIA and vimentin was confirmed by an yeast Two-Hybrid assay.Mutations in the gene for XIIIA have been detected in genomic DNA samples obtained from patients with XIIIA deficiency. An amino acid substitution of Arg260 by Cys had been predicted by molecular modeling and mechanics to result in instability of the XIIIA molecule. Rapid degradation of this mutant has been confirmed by an expression study in yeast. Rapid degradation of a novel Tyr283-Cys mutant has also been ascribed to its instability characterized in an expression system employing megakaryoblastoid MEGO1 cells that endogenously synthesize XIIIA.In order to understand the molecular pathology of XIII deficiency in vivo, XIIIA-knockout (KO) mice were functionally analyzed. Although homozygous XIIIA female KO mice were capable of becoming pregnant, most of them died due to excessive vaginal bleeding during gestaion. Abdominal incisions revealed that the uteri of the dead mice were filled with blood and that some embryos were much smaller than others within a single uterus. A series of histological examinations of the pregnant animals suggested that massive placental hemorrhage and subsequent necrosis developed in the uteri of the XIIIA KO mice on day 10 of gestation. This was true regardless of the genotypes of fetuses.