Two novel factor VII gene mutations in a Chinese family with factor VII deficiency

Using a minigene approach to characterize a novel splice site mutation in human F7 gene causing inherited factor VII deficiency in a Chinese pedigree

Factor VII deficiency which transmitted as an autosomal recessive disorder is a rare haemorrhagic condition. The aim of this study was to identify the molecular genetic defect and determine its functional consequences in a Chinese pedigree with FVII deficiency. The proband was diagnosed as inherited coagulation FVII deficiency by reduced plasma levels of FVII activity (4.4%) and antigen (38.5%). All nine exons and their flanking sequence of F7 gene were amplified by polymerase chain reaction (PCR) for the proband and the PCR products were directly sequenced. The compound heterozygous mutations of F7 (NM_000131.3) c.572-1G>A and F7 (NM_000131.3) c.1165T>G; p.Cys389Gly were identified in the proband's F7 gene. To investigate the splicing patterns associated with F7 c.572-1G>A, ectopic transcripts in leucocytes of the proband were analyzed. F7 minigenes, spanning from intron 4 to intron 7 and carrying either an A or a G at position -1 of intron 5, were constructed and transiently transfected into human embryonic kidney (HEK) 293T cells, followed by RT-PCR analysis. The aberrant transcripts from the F7 c.572-1G>A mutant allele were not detected by ectopic transcription study. Sequencing of the RT-PCR products from the mutant transfectant demonstrated the production of an erroneously spliced mRNA with exon 6 skipping, whereas a normal splicing occurred in the wide type transfectant. The aberrant mRNA produced from the F7 c.572-1G>A mutant allele is responsible for the factor VII deficiency in this pedigree.

Characterization of a Cys329Gly mutation causing hereditary factor VII deficiency

We have previously reported a homozygous Cys329Gly mutation in a Chinese patient with factor VII (FVII) deficiency. Others have found a heterozygous Cys329Gly mutation in the F7 gene from patients of three different pedigrees. However, none of the reports included the expression and characterization of the mutant FVII in vitro. To investigate the effect of Cys329Gly on FVII function, we carried out transient transfections of baby hamster kidney cells (BHK-21) with a mutant FVII construct and compared the results to those obtained using a wild-type FVII construct and vector control. The results demonstrate that the level of FVII:Ag secreted into the medium by transfected BHK-21 cells with mutant construct was not affected, but the coagulation activity of the mutant FVII was undetectable. We conclude that Cys329 is critical to FVII coagulation, and the replacement of cysteine 329 by glycine leads to the loss of coagulation activity in the patients, possibly the molecular basis for FVII deficiency in the patients.

Two novel cases of cerebral haemorrhages at the neonatal period associated with inherited factor VII deficiency, one of them revealing a new nonsense mutation (Ser52Stop)

Factor VII (FVII) is a plasma glycoprotein that plays a key role in the initiation of blood coagulation cascade. Inherited FVII deficiency is a rare autosomal recessive disorder with a wide heterogeneous clinical pattern. The severe form may be associated with intracranial haemorrhages occurring closely to birth with a high mortality rate. In the present article, we report two novel cases of neonatal intracerebral bleeding associated with FVII activity levels below 1% of normal. FVII genotyping investigations revealed particular genotypes including the deleterious Cys135Arg mutation and a novel Ser52Stop nonsense mutation at the homozygous state. Both mutations, through different mechanisms, are expected to be inconsistent with the production of functional FVII. These putative mechanisms are discussed through a review of the literature on phenotypic and genotypic characteristics of cerebral haemorrhages in severe inherited FVII deficiency.