The Arg(353)Gln polymorphism reduces the level of coagulation factor VII - In vivo and in vitro studies

Factor VII levels are regulated by environmental and genetic factors. Two polymorphisms, a G-to-A transversion at nucleotide 10976 resulting in Arg(353)Gln and a decanucleotide insert at position -323 in the 5'-flanking region of the factor VII gene, have been associated with a 20% to 25% reduction in plasma factor VII levels. However Arg(353)Gln almost always segregates on alleles containing the insert in UK and Italian populations, thereby making it impossible to independently evaluate the impact of Arg(353)Gln on factor VII levels in these ethnic groups. We have evaluated the influence of genotype on factor VII levels in 99 healthy Polish blood donors and observed that Arg(353)Gln frequently occurs in the absence of the insert. In univariate analysis, the mean levels of factor VII coagulant activity (VII:C) and factor VII antigen (VII:Ag) were significantly lower in 16 people who were heterozygous for Arg(353)Gln and the insert compared with 72 normal subjects who had neither Arg(353)Gln nor the insert (88.8% of normal and 83.1% versus 102% and 100%, P=.019 and P=.0003, respectively). In nine subjects heterozygous for Arg(353)Gln alone, VII:C and VII:Ag were significantly decreased compared with the normal subjects (81.9% and 83%, respectively, P=.007 and P=.004). In multivariate analysis, Arg(353)Gln but not the insert significantly reduced VII:C and VII:Ag after adjustment for age and plasma triglycerides (P<.05 and P=.02: respectively). To evaluate the mechanism responsible for reduced factor VII levels in individuals with Arg(353)Gln, we performed transient transfection assays with factor VII cDNA containing the base substitution resulting in Gln(353) and wild-type factor VII cDNA in COS-1 cells. The levels of VII:Ag in the cell lysates were similar, but the amino acid substitution significantly reduced factor VII secretion into the media to 74.9% of wild-type (P=.0001). Based on these in vivo and in vitro studies, we conclude that the Arg(353)Gln polymorphism alone can decrease plasma factor VII levels.