ABSTRACT
BACKGROUND AND OBJECTIVES: Although a large number of gene mutations have been characterized in patients with factor VII (FVII) deficiency, few naturally occurring mutations have been described in epidermal growth factor (EGF)-like domains. We investigated a 6-year old Italian girl who had low functional and antigenic FVII plasma levels. DESIGN AND METHODS: Plasma levels of FVII activity and antigen were evaluated in the propositus and her relatives. Mutation screening was performed by sequencing the FVII gene. The effect of the identified FVII mutations was investigated by protein expression in transfected cells. RESULTS: The propositus was shown to be a compound heterozygote for a known (Arg110Cys) and a novel (Asp123Tyr) missense mutation both occurring in the second EGF-like domain. In transfected cells, expression of the Arg110Cys mutation reduced the amount of intracellular and secreted FVII protein (48% and 18%, respectively). Likewise, cells transfected with the Asp123Tyr mutation gave rise to low intracellular (40%) and extracellular (4%) FVII antigen levels. In conditioned media, FVII procoagulant activity was reduced accordingly (10% and <1%, respectively). INTERPRETATION AND CONCLUSIONS: Transient expression of the identified FVII mutations caused severely reduced but detectable FVII antigen and activity levels. The present findings suggest that the two naturally occurring missense mutations identified within the second EGF-like domain severely affect FVII protein handling, impairing the correct folding of FVII.
Subject(s)
Epidermal Growth Factor/genetics , Factor VII Deficiency/genetics , Factor VII/genetics , Animals , Base Sequence , COS Cells , Chlorocebus aethiops , DNA Primers , Factor VII/metabolism , Factor VII Deficiency/blood , Humans , Mutation, Missense , Protein Folding , TransfectionABSTRACT
A 60-year-old Italian woman presenting with factor VLeiden mutation but a normal activated protein C (APC) resistance, low functional and antigenic factor (FV) plasma levels, was found to have a novel heterozygous Gly2032Asp substitution located on the same allele. In transfected cells, the Gly2032Asp mutation caused an approximately 2-fold reduction of the intracellular FV protein and a 9-fold reduction of the secreted protein, suggesting that the Gly2032Asp substitution acts in cis on the allele carrying the FVLeiden mutation and rescues the APC-resistance phenotype.
Subject(s)
Activated Protein C Resistance/genetics , Mutation, Missense , Activated Protein C Resistance/etiology , Factor V , Female , Heterozygote , Humans , Middle Aged , Molecular Sequence Data , PhenotypeABSTRACT
BACKGROUND AND OBJECTIVES: In carriers of the factor V (FV) Leiden mutation, different trans-acting gene variants (HR2 haplotype and FV Cambridge mutation) affect activated protein C (APC) sensitivity. Among a series of FV gene variants characterized, the Asp79His polymorphism appeared to be a good candidate for the modulation of FV activity. DESIGN AND METHODS: In a group of 150 apparently healthy subjects without the FV Leiden mutation and in 55 apparently healthy subjects with mutation, genotypes of the Asp79His polymorphism and of the HR haplotype were characterized and plasma levels of FV coagulant activity and APC ratios evaluated. RESULTS: In the group without the FV Leiden mutation, 16 subjects (10.7%) carried the His 79 allele and 15 subjects (10.0%) the HR2 haplotype. Two of them carried both gene variants. As compared to FV activity levels in non-carriers (106.4+18.5%), values were lower in subjects with the His79 allele (95.2+25.2%; p=0.025) and in those with the HR2 haplotype (93.7+16.2%; p =0.007). FV activity levels were further reduced in carriers of both FV gene variants (78.7+3.3%; p =0.009). APC values were similar among individuals carrying different FV genotypes. In the group with the FV Leiden mutation, APC ratios were lower in subjects carrying the His 79 allele (0.63; p =0.008) or the HR2 haplotype (0.63; p =0.026) than in subjects without (0.69) reflecting FV activity values. INTERPRETATION AND CONCLUSIONS: Present data suggest that carriership of the His79 allele modulate plasma levels of FV coagulant activity and, in subjects carrying the FV Leiden mutation, affects APC sensitivity.
Subject(s)
Activated Protein C Resistance/genetics , Factor V , Factor V/genetics , Mutation, Missense , Factor V/analysis , Humans , Phenotype , Polymorphism, GeneticSubject(s)
Amino Acid Substitution , Factor V Deficiency/genetics , Factor V/genetics , Mutation, Missense , Animals , Cattle , Cerebral Hemorrhage/etiology , Craniocerebral Trauma/complications , DNA Mutational Analysis , Factor V/chemistry , Factor V Deficiency/complications , Humans , Male , Middle Aged , Protein Conformation , Protein Folding , Protein Structure, Tertiary , Species Specificity , Structure-Activity RelationshipABSTRACT
A number of strongly linked polymorphisms within the Factor V gene (FV HR2 haplotype) has been identified as a cause of resistance to activated protein C, and has suggested a modest risk factor for vein thrombosis. We investigated the frequency of the HR2 haplotype in 433 consecutive patients with confirmed deep vein thrombosis and 326 controls. The HR2 haplotype was more frequent in patients (15.2%) than in controls (10.1%). The risk of thrombosis among carriers of this haplotype was significantly increased (odds ratio: 1.6 [95% CI: 1.0-2.5]). The estimated risk associated with the HR2 haplotype was 1.8 (95% CI: 1.1-2.9) in subjects with (n = 255), and 1.4 (95% CI: 0.8-2.4) in those without (n = 178) acquired risk factors for vein thrombosis. After adjustment for sex, FV Leiden and FII A20210 mutations, the estimated risk of vein thrombosis among carriers of the HR2 haplotype was 1.8 (95% CI: 1.1-2.8). Present data indicate that the HR2 haplotype is independently associated with vein thrombosis among individuals with a high-risk profile.