A NlaIII polymorphism within the human factor VII gene

A patient homozygous for a Gly354Cys mutation in factor VII that results in severely impaired secretion of the molecule, but not complete deficiency

We investigated the molecular basis of factor VII (FVII) deficiency in a Japanese woman who suffered occasional epistaxis. The patient had low levels of both FVII coagulant activity (FVII:C) and antigen (FVII:Ag) (5.0% and 7.3% of normal controls respectively). DNA sequence analysis of the FVII gene showed that the patient was homozygous for a mutation that resulted in a Cys for Gly354 substitution, a novel missense mutation in the catalytic domain. Haplotype analysis showed that this missense mutation was inherited from her consanguineous parents. Transient expression experiments showed that secreted FVII Cys354, FVII:C and FVII:Ag levels in conditioned media were reduced to 4% and 5%, respectively, of levels secreted from wild-type FVII. However, the intracellular FVII Cys354 was 67% that of normal recombinant protein. Immunohistochemical analysis showed that intracellular FVII:Ag from FVII 354Cys was present diffusely throughout the cytoplasm. Substitution of FVII 354Gly with amino acids other than Cys (Arg, Asp, Ser and Phe), did not produce a phenotype similar to FVII Cys354Gly. Molecular modelling indicated that FVII Gly354 was located outside the FVII heavy chain, and that Cys135 in the EGF2 domain, Cys262 in the catalytic domain and Cys127 all exist within 10 A of Gly354. Therefore, we propose that the introduction of an additional free cysteine residue in the FVII molecule results in the formation of illegitimate disulphide bonds and a mis-folded domain, leading to defective secretion.

Severe factor VII deficiency with recurrent intracranial haemorrhages owing to double heterozygosity for a splice site mutation of an IVS4 and a novel nonsense mutation in exon 8 (Gln211-->Term)

Genetic analysis of a 10-month-old Japanese baby boy with recurrent intrathoracic bleeding, cerebral haemorrhages and gastrointestinal bleeding secondary to severe factor VII (FVII) deficiency revealed evidence of two distinct mutations of FVII: a splice site mutation of G-->A at nucleotide 6071 in the IVS4 splice site and a novel nonsense mutation (Gln211-->Term) in exon 8. His bleeding was difficult to control without prophylactic infusion of FVII. We detected a heterozygous splice site mutation of the IVS4 in his mother and a heterozygous nonsense mutation in exon 8 (Gln211-->Term) in his father. The parents' FVII levels are both 50% of normal controls. The FVII:C in plasma from the proband was < 1.5% of normal controls. FVII:antigen (Ag) was < 1% of normal controls, using a monoclonal antibody (mAb) hVII-B101/1 that specifically reacts with FVII epidermal growth factor 1 (EGF-1), and 5% of normal controls, using a rabbit polyclonal antibody against human FVII. After immunoadsorption with mAb hVII-B101/B1-Sepharose 4B, FVII levels of both the proband and his mother were 5% of normal controls; after immunoadsorption the FVII levels of normal subjects were < 1%. We hypothesize that secretion of a small amount of dysfunctional FVII lacking EGF-1 into the circulation accounts for this observation.

A new mutation in the HNF4 binding region of the factor VII promoter in a patient with severe factor VII deficiency

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.

A new mutation in the HNF4 binding region of the factor VII promoter in a patient with severe factor VII deficiency

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.