Rapid FSAP Genotyping of the E393Q (Marburg II) and G534E (Marburg I) Polymorphisms on the LightCycler in a Multiplex PCR Using Two Fluorescently Labeled Probe Sets

The Factor VII-activating protease (FSAP) is a plasma serine protease that acts as an activator of factor VII, independently of tissue factor, promoting the coagulation cascade and it activates pro-urokinase in the fibrinolytic pathway. Two single nucleotide polymorphisms (SNPs) in the coding region of the FSAP gene that lead to amino acid substitutions within the serine protease domain are presently discussed to be involved in the formation of atherosclerosis leading to carotid stenosis, cardiovascular diseases, and thromboembolic disorders. The G534E polymorphism, also known as Marburg I, is a guanine to adenine substitution that is found in about 5% of the population and impairs the in vitro capacity to activate pro-urokinase while the biological effect of the second variant (E393Q), also known as the Marburg II, has not yet been identified. Based on the properties to impair the pro-urokinase activity and their association with the incidence and progression of carotid stenosis it is conceivable that genotyping of this allelic variants is potentially interesting for routine genotyping of risk patients. We here describe the development of a novel LightCycler-based methodology allowing simultaneous genotyping of both allelic variants. The different genotypes could be identified easily and clearly by the generation of characteristic fluorescence melting peaks. The outlined methodology will be helpful for routine genotyping of these FSAP variants.