Factor VII deficiency in a mixed breed dog.
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Abnormal bleeding following routine orchectomy of a 5-month-old mixed breed was determined to be due to factor VII deficiency. Although pedigree information was unavailable, failure to respond to vitamin K therapy and the absence of a plasma coagulation inhibitor suggested that the factor VII deficiency was likely inherited rather than acquired. (+info)
Combined factor VII/protein C deficiency results in intrauterine coagulopathy in mice.
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To determine whether an additional loss of the coagulation factor VII (FVII) gene influenced the coagulopathy observed in protein C gene-deficient (PC(-/-)) embryos and neonates, we crossed mice doubly heterozygous for the factor VII (FVII(+/-)) and protein C (PC(+/-)) genes to produce offspring possessing the 9 predicted genotypic combinations. FVII(-/-)/PC(-/-) embryos, although present at their expected Mendelian frequency, displayed a phenotype that had not been observed in either the FVII or PC singly deficient embryos. At E12.5 days postcoitum (dpc), FVII(-/-)/PC(-/-) embryos demonstrated an intra- and extravascular coagulopathy that progressed with substantial concomitant hemorrhage and peripheral edema by E17.5dpc, resulting in mortality immediately after birth. FVII(+/-)/PC(-/-) embryos showed a less severe phenotype, suggesting a gene dosage effect. The lack of rescue of PC(-/-) embryos and neonates and augmented coagulopathy resulting from an additional heterozygous or homozygous FVII deficiency are probably due to increased factor Xa and thrombin generation, resulting from loss of FVIIa-dependent tissue factor pathway inhibitor function and the absence of control at the levels of factors Va and VIIIa. The presence of fibrin in embryos in the absence of fetal FVII suggests that significant clot-generating potential exists outside of the embryonic factor VII-dependent pathway. (+info)
Modulation of factor VII levels by intron 7 polymorphisms: population and in vitro studies.
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Previous studies have established that factor VII gene (F7) polymorphisms (5'F7 and R353Q) contribute about one-third of factor VII (FVII) level variation in plasma. However, F7 genotyping in patients with cardiovascular disease has produced conflicting results. Population and expression studies were used to investigate the role of intron 7 (IVS7 ) polymorphisms, including repeat and sequence variations, in controlling activated FVII (FVIIa) and antigen (FVIIag) levels. Genotype-phenotype studies performed in 438 Italian subjects suggested a positive relation between the IVS7 repeat number and FVII levels. The lowest values were associated with the IVS7 + 7G allele. The screening of 52 patients with mild FVII deficiency showed an 8-fold increase in frequency (8%) of this allele, and among heterozygotes for identical mutations, lower FVII levels were observed in the IVS7 + 7G carriers. This frequent genetic component participates in the phenotypic heterogeneity of FVII deficiency. The evaluation of the individual contribution of polymorphisms was assisted by the expression of each IVS7 variant, as a minigene, in eukaryotic cells. The novel quantitative analysis revealed that higher numbers of repeats were associated with higher mRNA expression levels and that the IVS7 + 7G allele, previously defined as a functionally silent polymorphism, was responsible for the lowest relative mRNA expression. Taken together, these findings indicate that the IVS7 polymorphisms contribute to the plasmatic variance of FVII levels via differential efficiency of mRNA splicing. These studies provide further elements to understand the control of FVII levels, which could be of importance to ensure the hemostatic balance under pathologic conditions. (+info)
A new mutation in the HNF4 binding region of the factor VII promoter in a patient with severe factor VII deficiency.
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Investigation of the molecular basis of a severe factor VII (fVII) deficiency revealed compound heterozygosity in the fVII gene. On the paternal allele the patient had 3 structural gene abnormalities frequently associated with fVII deficiency. A new mutation, a C to T transition at position -55 relative to the translational start site, was found on the maternal allele. The study demonstrates that this mutation partially impeded binding of the transcriptional activator, hepatic nuclear factor 4, to the fVII promoter while greatly reducing reporter gene expression in hepatic cells. (Blood. 2000;96:4370-4372) (+info)
Abnormal secretion and function of recombinant human factor VII as the result of modification to a calcium binding site caused by a 15-base pair insertion in the F7 gene.
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A case of a novel mutation in the F7 gene that results in factor VII coagulant activity (VII:c) of less than 1% and VII antigen (VII:Ag) levels of 10% is presented. DNA analysis revealed a homozygous 15-base pair (bp) in-frame insertion-type mutation at nucleotide 10554. This insertion consisted of a duplication of residues leucine (L)213 to aspartic acid (D)217 (leucine, serine, glutamic acid, histidine, and aspartic acid), probably arising by slipped mispairing between 2 copies of a direct repeat (GCGAGCACGAC) separated by 4 bp. Molecular graphic analyses showed that the insertion is located at the surface of the catalytic domain in an exposed loop stabilized by extensive salt-bridge and hydrogen bond formation at which the calcium binding site is located. The mutation probably interferes with protein folding during VII biosynthesis and/or diminishes functional activity through the loss of calcium binding. In vitro expression studies demonstrated that the levels of VII:Ag in lysates of cells transfected with wild type VII (VIIWT) were equivalent to those with mutant type VII (VIIMT), but the level of secreted VIIMT was 5% to 10% that of VIIWT. Pulse chase studies demonstrated that VIIMT did not accumulate intracellularly, and studies with inhibitors of protein degradation showed that recombinant VIIMT was partially degraded in the pre-Golgi compartment. Accordingly, only small amounts of VIIMT with undetectable procoagulant activity were secreted into conditioned media. These results demonstrate that a combination of secretion and functional defects is the mechanism whereby this insertion causes VII deficiency. (+info)
Analysis of the genotypes and phenotypes of 37 unrelated patients with inherited factor VII deficiency.
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Severe inherited factor VII (FVII) deficiency is a rare autosomal recessive disorder with a poor relationship between FVII coagulant activity and bleeding tendency. Both clinical expression and mutational spectrum are highly variable. We have screened for mutations the FVII gene of 37 unrelated patients with a FVII coagulant activity less than 5% of normal pooled plasmas. The nine exons with boundaries and the 5' flanking region of the FVII gene were explored using a combination of denaturing gradient gel electrophoresis and direct DNA sequencing. This strategy allowed us to characterise 68 out of the 74 predicted FVII mutated alleles. They corresponded to a large panel of 40 different mutations. Among these, 18 were not already reported. Genotypes of the severely affected patients comprised, on both alleles, deleterious mutations which appeared to be related to a total absence of activated FVII. We suggest that this absence of functional FVII can explain the severe clinical expression. Whether a small release of FVII is sufficient to initiate the coagulation cascade and to prevent the expression of a severe phenotype, requires further investigations. (+info)
Pharmacokinetic evaluation of recombinant, activated factor VII in patients with inherited factor VII deficiency.
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BACKGROUND AND OBJECTIVES: Recombinant factor VIIa (rFVIIa) has been widely used in the treatment of bleedings occurring in hemophiliacs with inhibitors. Very few reports exist on the use of rFVIIa in patients with inherited FVII deficiency. Pharmacokinetic studies on rFVIIa have been performed exclusively in hemophiliacs, patients with cirrhosis or volunteers pretreated with acenocoumarol. The aim of this study was to evaluate the kinetics of rFVIIa in patients naturally deficient of FVII. DESIGN AND METHODS: A single dose kinetic study with rFVIIa was performed in 5 patients affected by severe congenital deficiency of factor VII in order to evaluate the true kinetic parameters of rFVIIa without the interference of FVII. Two dosages, 15 and 30 microg/kg, were used in a crossover schedule. FVII:C and FVIIa concentration/time curves were analyzed by a model-independent method. Antithrombin (AT), prothombin fragment 1+2 (F1+2) and tissue factor pathway inhibitor (TFPI) were assayed. RESULTS: No differences emerged between the dosages with respect to dose-independent parameters [total body clearance (CL), volume of distribution area (VdArea), mean residence time (MRT)]. No significant changes of AT, TFPI, and F1+2 were observed. Comparing the results with those of other studies performed in adult hemophiliacs, in patients affected by cirrhosis or in volunteers on oral anticoagulant therapy (OAT), CL and VdArea of rFVIIa were definitely higher and in vivo recovery was lower. INTERPRETATION AND CONCLUSIONS: These findings suggest that the kinetics of rFVIIa are not dose-dependent. In the absence of FVII, the changes of VdArea and CL may be in agreement with a mechanism of competition between FVII and rFVIIa for tissue factor binding. (+info)
Residual factor VII activity and different hemorrhagic phenotypes in CRM(+) factor VII deficiencies (Gly331Ser and Gly283Ser).
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Two cross-reacting material-positive (CRM(+)) factor VII (FVII) mutations, associated with similar reductions in coagulant activity (2.5%) but with mild to asymptomatic (Gly331Ser, c184 [in chymotrypsin numbering]) or severe (Gly283Ser, c140) hemorrhagic phenotypes, were investigated. The affected glycines belong to structurally conserved regions in the c184 through c193 and c140s activation domain loops, respectively. The natural mutants 331Ser-FVII and 283Ser-FVII were expressed, and in addition 331Ala-FVII and 283Ala-FVII were expressed because 3 functional serine-proteases bear alanine at these positions. The 331Ser-FVII, present in several asymptomatic subjects, showed detectable factor Xa generation activity in patient plasma (0.7% +/- 0.2%) and in reconstituted system with the recombinant molecules (2.7% +/- 1.1%). The reduced activity of recombinant 283Ala-FVII (7.2% +/- 2.2%) indicates that the full function of FVII requires glycine at this position, and the undetectable activity of 283Ser-FVII suggests that the oxydrile group of Ser283 participates in causing severe CRM(+) deficiency. Furthermore, in a plasma system with limiting thromboplastin concentration, 283Ser-FVII inhibited wild-type FVIIa activity in a dose-dependent manner. (+info)