[Novel frame-shift mutation of 540 A deletion in GP IIb gene from a patient with Glanzmann thrombasthenia].

OBJECTIVE: To explore the molecular mechanism of Glanzmann thrombasthenia (GT). METHODS: All 45 exons of alphaIIb and beta3 subunit genes as well as their splicing sites were amplified by polymerase chain reaction(PCR) with 40 primer pairs, and then the PCR products were used to screen the gene mutation by single strand conformation polymorphism-polyacrylamide gel electrophoresis (SSCP-PAGE). The mutation was further confirmed by direct DNA sequencing. RESULTS: A DNA band alterated migration was detected after SSCP-PAGE. DNA sequencing showed that a base deletion within the band at the site of 540 in GPIIb gene(540A) was found. CONCLUSION: The frame-shift mutation caused by the deletion of 540A in GPIIb gene is a novel mutation which is a genetic defect in patients with GT.

[3 polymorphisms of gene GP IIb and the function of GP IIb T13959 G in the platelet transfusion refractoriness].

OBJECTIVE: To investigate the relationship among 3 polymorphisms of GP IIb and the function of GP IIb T13959 G in the platelet transfusion refractoriness(PTR). METHODS: The 26th exon, the 30th exon and the 21st intron of gene GP IIb in 110 individuals were amplified by polymerase chain reaction (PCR), and the PCR products were analyzed with single-strand conformation polymorphism(SSCP) and sequenced to investigate whether there was linkage among the polymorphisms of the gene. Human platelet antigen-3 (HPA-3) gene frequency was detected by Fok I enzyme in 147 patients with hematologic diseases, and was compared with that in 110 normal individuals. Forty-four patients who received apheresis platelet transfusion repeatedly were randomly divided into the HPA-3 homotype group and the control group. The antibodies of the platelet were detected after 3 times of platelet transfusion. RESULTS: There were polymorphisms of gene GP IIb in the 26th, 30th exon and the 21st intron, and the mutations were: T changed into G in 13,959 th of the 26th exon; C changed into T in 16,997 th of the 30th exon; the 9 bps deletion occurred in 11,996-12,004 th of the 21st intron. The 3 polymorphisms had synchronization in the individuals. The results of Fok I enzyme indicated that the frequency of HPA-3a was 83.6% (92/110)and 81.9%(119/147), and that of HPA-3b was 16.4%(18/110) and 19.1%(28/147) in the normal individuals and the patients respectively. There was no significant difference between the patients and normal individuals (P>0.05). After the platelet transfusion, the antibodies of all the cases of the homotype platelet transfusion were negative, but the antibodies in 2 cases of the control group were positive, and there was antibody to HPA-3a in one of the antibodies positive cases. CONCLUSION: (1)There is close linkage among the polymorphisms of gene GP IIb, which is T->G in 13 959 th of the 26th exon, C->T in 16,997 th of the 30th exon, and the 9 bps deletion in 11,996-12,004 th in the 21st intron. (2)The gene frequency of HPA-3a/3b is similar in the normal individuals and patients with hematologic diseases. (3) HPA-3 system may be one of the reasons for PTR in Chinese.

Effects of integrin alpha IIb(R995A) mutation on receptor affinity and pp125 (FAK) phosphorylation.

OBJECTIVE: To investigate the role of cytoplasmic domain of integrin alpha IIb in platelet signal transduction. METHODS: Binding capacity of integrin alpha IIb(R995A) to antibody platelet activation complex-1 (PAC-1) and pp125 focal adhesion kinase (FAK) phosphorylation of cells were detected by flow cytometry, immune precipitation, and Western blotting. RESULTS: Without activation, wild-type alpha IIb beta3 Chinese hamster ovary (CHO) cells failed to bind to PAC-1, but mutant chimera alpha IIb(R995A)beta3 CHO cells were able to bind with PAC-1. Furthermore, phosphorylation of pp125 (FAK) in wild-type alpha IIb beta3 CHO cells occured only when cells were adhered to fibrinogen, but could not be detected in bovine serum albumin suspension. However in the mutant chimera group, it could be detected in both conditions. CONCLUSION: The mutation in integrin alpha IIb(R995A) alters its affinity state as a receptor, thus also mediating cytoplasmic signal transduction leading to the phosphorylation of pp125 (FAK) without ligand binding.

[Observation on tissue factor pathway during the onset of acute cerebral infarction].

OBJECTIVE: To establish the possible relationship between some coagulation factors and the onset of acute cerebral infarction (ACI). METHODS: The study population consisted of 71 patients with ACI confirmed by CT and 50 age-matched healthy volunteers. Blood samples were obtained during the onset period of ACI. Tissue factor (TF) and tissue factor pathway inhibitor (TFPI) activity in plasma were assayed with the chromogenic assay. Plasma TF and TFPI antigen were measured with enzyme linked immunoadsorbent assay (ELISA). Plasma F VII coagulation activity (F VII: C) and F VIII coagulation activity (F VIII: C) were developed in the one-stage system. Plasma prothrombin (FII) was determined with Ecarin assay. Plasma fibrinogen (Fbg) was measured with thrombin assay. Plasma antithrombin III activity (ATIII) was determined using heparin cofactor activity assay. RESULTS: Compared with the control, plasma TF activity and antigen in patients with ACI were significantly higher (both P<0.05). But plasma TFPI activity and antigen were remarkably lower in the ACI group (both P<0.05). Plasma F VII: C was significantly higher (P<0.01), and F VIII: C was markedly lower (P<0.05). Plasma FII was remarkably higher (P<0.01). Similarly the Fbg was significantly higher in the ACI than that in the control group (P<0.01), whereas ATIII was significantly lower (P<0.01). CONCLUSION: The initiation of TF pathway is contributed to the onset of ACI and the blood is in hypercoagulable state during the early period of ACI.

[Effect of GPI-PLD on adhesion function of bone marrow mononuclear cell from patients with myeloid leukemia and its mechanism].

To explore the effect of glycosyl-phosphatidyl inositol-specific phospholipase D (GPI-PLD) on the adhesion function of bone marrow mononuclear cell from patients with myeloid leukemia and analyze its mechanism, the activity of GPI-PLD in bone marrow mononuclear cell from the patients were measured by using GPI-anchored placental alkaline phosphatase (PLAP) as substrate and Triton-X114 partitioning; the adhesion rate and CD24 expression of these cells were measured by MTT and immunohistochemical method respectively, when these cells were or were not treated by 1 mmol/L 1,10-phenanthroline for 5 hours. The results showed that the GPI-PLD activity of bone marrow mononuclear cells from the patients was significantly inhibited after being treated by 1 mmol/L 1, 10-phenanthroline for 5 hours [(42.08 +/- 7.21)% vs (5.4 +/- 2.96)%], while the adhesion rate and the expression of CD24 of these cells were increased [(49.78 +/- 26.73)% vs (61.19 +/- 29.14)%, (16.02 +/- 9.68)% vs (18.5 +/- 11.14)%, respectively)]. It is concluded that depression of GPI-PLD activity can increase the adhesion rate of bone marrow mononuclear cells from the patients while the CD24 expression is enhanced.

[Expression of coagulation factor IX in human CD34 + hematopoietic stem cells by adeno-associated virus 2].

OBJECTIVE: To investigate the expression of human coagulation factor IX (hFIX) gene in human umbilical cord blood (CB) CD34+ cells which was transfected with recombinant adeno-associated virus 2 (rAAV-2). METHOD: The CD34+ cells were transfected with rAAV-2/hFIX and cultured for 21 days for inducing differentiation into myeloid, erythroid and megakaryocytes, respectively. The expression of hFIX was studied at mRNA, protein and biological activity levels. The cytotoxicity of rAAV-2 to CD34+ cells was evaluated by cell proliferation, cell vitality, CD antigen expressions and CFU yields. RESULTS: The hFIX mRNA was expressed in the cultured cells which was verified by RT-PCR and DNA sequencing. An elevated level of hFIX expression and biological activities were detected with a maximum amount of 14.10 ng/10(6) cell x 24 h. During the period of 21 day culture, the cell vitality, cell proliferation, CD antigen expression and CFU yields between the transfected and un-transfected groups had no difference(P > 0.05). CONCLUSION: The human CB CD34+ cells are able to produce functional hFIX after transduction by rAAV-2/hFIX. The cell proliferation and differentiation capacities of the host CD34+ cells were not affected by rAAV-2.

[Effect of the defect of integrin alpha II b beta 3 on the inside-out signal transduction in platelets].

OBJECTIVE: To investigate the effect of the defect of integrin alpha II b beta 3 on the inside-out signal transduction in platelets. METHODS: The transfected cDNA, its expression and the ability of cells binding to PAC-1 and fibrinogen were investigated by RT-PCR, DNA sequence analysis, flow cytometry and Western blotting. RESULTS: The integrin alpha II b beta 3 level in the patients with Glanzmann's thrombasthenia was significantly lower than that of the normal subjects and the platelets of the patients failed to bind PAC-1 activated by ADP. There were both C3077G and G3078C mutations in exon 30 of mutant alpha II bR995A beta 3 cDNA, which resulted in an amino acid substitution arginine (R) 995 to alanine (A). CHO cells transfected with wild-type alpha II b beta 3 or mutant alpha II bR995A beta 3 cDNA respectively expressed normal alpha II b beta 3 and mutant alpha II bR995A beta 3. When cells were not activated, wild-type alpha II b beta 3 CHO cells failed to bind PAC-1, but could adhere to fibrinogen, but mutant chimera alpha II bR995A beta 3 CHO cells were able to bind PAC-1 and exhibited high affinity binding fibrinogen. CONCLUSION: The point mutation in integrin alpha II bR995A can induce the inside-out signal transduction in platelets, and have integrin alpha II bR995A beta 3 locked into an activation state; the defect of alpha II b beta 3 in patients with GT impairs the inside-out signal transduction mediated by alpha II b beta 3 in platelets and the adhesive functions of platelets.