Molecular characterization of a factor VII deficient patient supports the importance of the second epidermal growth factor-like domain

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.