[Correlation of Thrombosis and Prothrombotic State with Coagulation Factor V Gene Polymorphism and APCR. HHcy].

OBJECTIVE: To investigate the correlation of patients with thrombosis or prothrombotic status with hyperhomocysteinemia (HHcy), activated protein C-resistance(APCR) and gene polymorphism of coagulation factor V. METHODS: Three hundred healthy voluteers were selected as controls, 223 cases of thrombosis (80 cases of cerebral infarction of CT, the MI of 82 cases of myocardial infarction, venous thrombosis of VTE 61 cases), 270 cases of patients with prothrombotic state (76 cases of pregnancy disease of PIH, 62 cases of chronic obstructive pulmonary disease (COPD), 60 cases of diabetes(DM) and 72 cases of cancer) were enrolled in this study. The plasma APCR and hyperhomocysteinemia were detected by APTT coagulation method and cycling enzyme method respectively, and restriction fragment length polymorphism(RFLP) were was used to detect the gene polymorphism of FV G1691-A, G1091-C and A1090-G in the patient and control groups. RESULTS: APCR positive rate was 62.29% and 7.33%, and the positive hyperhomocysteinemia accounted for 68.42% and 10.00% respectively in the group of the patients with venous thrombosis and the normal control group. 3 cases of heterozygous FV gene mutations were found in the APCR-positive patients with venous thrombosis. CONCLUSION: HHcy possitive rate of patients with venous thrombosis is signiticantly higher than that in control, the HHcy is one of the important causes resulting in thrombosis, the patients with venous thrombosis have proved to be with APCR, and the possitive APCR may be related with the coagulation factor V gene polymorphism.

[Molecular mechanisms of recurrent venous thrombosis in two pedigrees with type I antithrombin deficiency].

OBJECTIVE: To investigate the clinical phenotype, genotype and molecular mechanism of recurrent venous thrombosis in two Chinese pedigrees with type I antithrombin (AT) deficiency. METHODS: The routine coagulation screening tests were detected, thrombin generation tests was performed to evaluate the hypercoagulation. Anticardiolipin antibody (ACA) and lupus anticoagulant (LA) were detected with enzyme-linked immunosorbent assay (ELISA) and diluted viper venom time assay (DVVT), respectively. The activities of protein C, protein S and AT (PC:A, PS:A, AT:A) were tested with chromogenic substrate assay or clotting method. The antigen of AT (AT:Ag) was performed with immunoturbidimetry methods. Western blot was used to analyze the molecular weight (MW) and the plasma levels of AT:Ag. All 7 exons and the flanking sequences were amplified by PCR. The mutation of AT gene and thrombophilia associated gene polymorphisms were analyzed by direct DNA sequencing. The expression plasmid of Ala404Asp mutant was constructed with site-directed mutagenesis method based on the wild-type (WT) AT cDNA contained in pcDNA 3.1 vector, and transiently expression of AT WT and the Ala404Asp mutant was performed using HEK293T cells. Cultured supernatant and cell lysates were collected and measured for AT:Ag by ELISA and Western blot. RESULTS: The results of routine coagulation tests in two probands were normal, thrombin generation tests indicated that proband 1 presented hypercoagulable state with 2.8 and 1.5 times higher of the endogenous thrombin potential (ETP) and peak height compared with that of normal, respectively. The levels of PC:A, PS:A, ACA and LA were normal. AT:A in proband 1 and proband 2 were 45% and 32%, and AT:Ag were almost half of the normal (121 mg/L and 158 mg/L), respectively. The results of Western blot showed that both probands' plasma levels of AT:Ag were lower than the normal pooled plasma and MW was normal. Two heterozygous mutations of g.3291C→T(Thr98Ile), g.13863C > A(Ala404Asp) were identified in the probands, respectively. No proband had venous thrombosis associated gene polymorphisms. Expression in vitro showed that AT:Ag in culture media and lysates of Ala404Asp are 4.8% and 60.6% of that of WT, respectively. CONCLUSION: Thr98Ile and Ala404Asp mutation of AT gene significantly correlate with recurrent venous thrombosis in the two probands, respectively. Ala404Asp has not been described before. The mutant Ala404Asp protein can not be expressed due to impaired secretion and increased intracellular degradation, resulting in type I AT deficiency.

[Preparation and characterization of a monoclonal antibody against human c-Kit].

AIM: To prepare anti-c-Kit monoclonal antibodies and characterize their specificity of epitope recognition. METHODS: cDNA encoding human c-Kit extracellular domain was constructed into a procaryotic expression vector pQE30 and the correctness of the reconstructed plasmid pQE30-KitD4-5 was verified by sequencing. The plasmid was transformed into E.coli M15 strain. Recombinant 6 x His pQE30-KitD4-5 was expressed after induction by IPTG for 4 h. Then SDS-PAGE results suggested that the products mainly formed inclusion bodies. The fusion protein was further purified with Ni-NTA-His affinity chromatography and then used to immunize BALB/c mice. The hybridomas were achieved by fusing the immunized spleen cells with the Sp2/0 myeloma cell line. The positive clones were screened by FCM with CHO-hKit cells. Hybidoma clones secreting anti-c-Kit antibodies were further subcloned and investigated for their biological activities by Western blot, rapid isotyping analysis and FCM. RESULTS: Recombinant human c-Kit fusion proteins were in vitro expressed and purified to be used as immunogen. One stable hybridoma cell line, which continuously secrets specific anti-c-Kit monoclonal antibody ((SRJ1)) was established. The biological activity studies showed that the monoclonal antibody recognized the natural c-Kit expressed on the Kasumi leukemia cell line, but failed to bind to the normal human peripheral blood cells. Interestingly, this monoclonal antibody failed to recognize a subpopulation of Kasumi cells that is reactive with the commercial anti-c-Kit mAb Ab81 suggesting that the c-Kit expressed by this subpopulation contains some sequencial and/or structural aberrations that are distinguishable by mAb SRJ1. CONCLUSION: With an immunization procedure using purified recombinant human c-Kit fusion proteins. a hybridoma cell line continuously and stably secreting anti-c-Kit monoclonal antibody has been established. The monoclonal antibody SRJ1 specifically recognizes human c-Kit expressed on the leukemia cells, and may provide a novel approach to analyze the possible structural variations of c-Kit expressed by different cells.

[Molecular mechanisms of Glanzmann thrombasthenia caused by alphaII b P126H mutation: an in vitro experiment].

OBJECTIVE: To explore the molecular mechanisms of Glanzmann thrombasthenia caused by alpha IIb P126H mutation. METHODS: Eukaryotic vector of alpha IIb P126H was constructed by PCR site-directed mutagenesis and then co-transfected with eukaryotic vector PCDM8 II a expressing the subunit beta3 into human renal epithelial cells of the line 293& and Chinese hamster ovarian cancer cells of the line CHO after sequencing. The membrane expression of alpha IIb P126H mutant was analyzed by flow cytometry and the whole expression was confirmed by Western blotting. The alpha IIb P126H mutant subcellular localization was determined by laser confocal scanning microscopy. RESULTS: The 293T cells cotransfected with cDNAs of mutated alpha IIb and wild-type beta3 failed to express alpha II bbeta3 on the cell surface as shown by FACS. Western blotting of the cell lysate showed no detectable mature alpha IIb. Immunofluorescence studies demonstrated proa II bbeta3 complex colocalized with an endoplasmic reticulum (ER) marker, but showed minimal colocalization with an Golgi marker. CONCLUSION: The P126H mutation in alpha IIb prevents transport of the pro-alpha II bbeta3 complex from ER to the Golgi body, thus hindering its maturation and surface expression. The impaired alpha II bp33 transport is responsible for the thrombasthenia.

[Antithrombin deficiency due to heterozygous antithrombin gene mutation and a pedigree study].

OBJECTIVE: To identify the antithrombin (AT) phenotype and gene mutation of a kindred with hereditary antithrombin deficiency. METHODS: Plasma AT activity and AT antigen level of the propositus and his kindred members were determined with chromogenic substrate method and immunoassay, respectively. All the seven exons and intron-exon boundaries of antithrombin gene were analyzed by PCR and direct sequencing of amplified PCR products from the propositus. RESULTS: The propositus AT antigen level was normal but his AT activity was only 65% of normal value suggesting that he had type II AT deficiency. A heterozygous G13830A mutation in exon 6 resulting in Arg393His missense mutation in his AT polypeptide was identified in the propositus. The same phenotype and gene mutation were found in other 3 kindred members. CONCLUSION: The type II AT deficiency found in this kindred is caused by heterozygous G13830A mutation in AT gene.

Factor X Shanghai and disruption of translocation to the endoplasmic reticulum.

BACKGROUND AND OBJECTIVES: Most secreted proteins, including coagulation factor X (FX), are synthesized with a signal peptide, which is necessary for targeting the nascent polypeptide into the endoplasmic reticulum. Characterization of naturally occurring mutations may provide insights into the functional roles of the amino acids in the signal peptide. DESIGN AND METHODS: A 52-year old male patient with type I FX deficiency was studied. Mutations were searched for by FX gene (F10) sequencing. The wild-type and the mutant FX proteins were expressed in transfected cells and then immunological assays were performed. Pulse-chase experiments and cell-free expression studies were conducted to determine the cellular fate of the mutant FX molecules. RESULTS: The patient we studied was homozygous for a substitution of arginine for serine at codon -30 in the signal sequence of F10. Immunoassays detected low FX antigen levels in both the conditioned media and lysates of the cells expressing the mutant protein. Pulse-chase analysis showed that only trace amounts of the mutant FX protein were detectable in the conditioned media, and that the mutant molecules did not accumulate inside the cells either. The results of cell-free expression studies showed that although the transcription and translation of the mutant construct were normal, no post-translational processing, such as N-linked glycosylation, occurred in the presence of microsomes. INTERPRETATION AND CONCLUSIONS: These findings suggest that substitution of a neutral polar amino acid, serine by arginine, in the hydrophobic core of FX signal peptide severely impairs the ability of the protein to enter the endoplasmic reticulum and results in FX deficiency.

[Type I hereditary protein C deficiency due to C5498T mutation in protein C gene].

OBJECTIVE: To identify the gene mutation in a Chinese pedigree of type I hereditary protein C deficiency. METHODS: The plasma levels of protein C activity (PC:A), protein C antigen (PC:Ag), protein S activity, and anti-thrombin activity (AT:A) of the propositus, male, aged 7, and 11 members of the pedigree were detected using ELISA and chromogenic assay respectively. All of the nine exons and intron-exon boundaries of protein C gene of the propositus were analyzed by direct sequencing of the corresponding amplified PCR products in DNA from the propositus. Restriction enzyme site analysis was used to confirm the mutation. RESULTS: The plasma concentrations of protein C activity and antigen of the propositus were 26% and 1.43 g/L respectively. The PC:Ag and PC:A of his father were normal. Decreased PC:A level was seen in his mother and 4 of his maternal pedigree. PS:A and AT:A were all normal in all of the pedigree members. A C5498T heterozygous mutation in exon 3, resulting in the substitution of Arg for Trp at the 15th amino acid, was identified in the propositus and 8 of his relatives. This mutation was confirmed by restriction enzyme site analysis. Mutations C/T at position 2405, A/G at position 2418, and A/T at position 2583 in the protein C promoter region were confirmed in the propositus and all members of the pedigree. CONCLUSION: C5498T heterozygous mutation in exon 3 of protein C gene, first reported in China, leads to type I hereditary.

[Effective and stable in vitro expression of human coagulation factor VIII by retrovirus-based plasmid vector coupled with polyamidoamine dendrimer].

OBJECTIVE: To demonstrate the effectiveness of a retrovirus-based plasmid vector coupled with nanometer material-polyamidoamine (PAMAM) dendrimer in stable gene expression of FVIII in vitro and to study the cytotoxicity of PAMAM. METHODS: The retrovirus-based plasmid vector pLNC-FVIII BD was generated by cloning a B-domain-deleted (760aa - 1639aa) FVIII cDNA (FVIIIBD cDNA) into retroviral vector pLNCX. The complex that contained PAMAM and pLNC-FVIII BD transfer FVIII BD cDNA into NIH3T3 cell line. In day 2, 5, 10, 15, 30 after transferring, the antigen and procoagulant activity of human FVIII in the cell culture medium were measured by ELISA assay and one-stage method, respectively. RT-PCR was performed for the detection of FVIII BD mRNA. Inhibitory percentage of cell vitality was used for cytotoxicity of PAMAM. RESULTS: Human FVIII was expressed for 30 days by transfected cells. The mean procoagulant activity of secreted FVIII in these 30 days was 0.929 U/ml, and the FVIII antigen was 0.188 micro g/ml by 10(6) cells in 24 hours, respectively. The level of FVIII didn't significantly decreased during these days. Inhibitory percent of cell vitality was only 5.32%. CONCLUSION: PAMAM could effectively transfer pLNC-FVIII BD into NIH3T3 cells and FVIII could be stably and effectively expressed by the transfected cells. Cytotoxicity of PAMAM was low.

[Molecular mechanisms of two novel mutations of factor XIII gene resulting in hereditary coagulation deficiency].

OBJECTIVE: To investigate the mechanisms of two novel missense mutations of factor XIIIA subunit gene (Arg77-->Cys,Ser413-->Trp) in the pathogenesis of hereditary factor XIII deficiency. METHODS: Site-directed mutagenesis was conducted to obtain 2 mutant human XIII A recombinant plasmids, mut-PCI/FXIIIA. Normal wild type factor XIII A recombinant plasmid, wt-PCI/FXIIIA, and mut-PCI/FXIIIA, were transfected into cultured COS7 cells line, renal fibroid cell of African green monkey using Superfect reagent respectively, The expression levels of DNA, RNA and protein of human factor XIII, both wild type and mutant, were detected by PCR, RT-PCR and Western blotting. Pulse-chase experiment was used to look into the changing of factor XIII A in the cytoplasm. Factor XIIIA activity was assayed by Biotin-pentylamine incorporation technique. RESULTS: The mRNA levels of the two mutants in transfected cells were similar to that of the wild type factor XIIIA. But the amount of mutant factor XIIIA protein and its activity in cells decreased markedly, even disappeared. Pulse-chase experiment revealed that at the two mutants existed chase time 0.5 h and 1 h considerable amounts in cells and then disappeared rapidly later. CONCLUSION: The 2 mutations of the factor XIIIA cause the instability, degradation, and rapid disappearance of FXIIIA in cytoplasm, thus resulting in hereditary factor XIII deficiency.