[Analysis of Phenotype and L12R Mutation in Signal Peptide and 3' Non-translation Region c11814-insAA Mutation of F7 Gene in a Family with Hereditary Coagulation Factor VII Deficiency].

OBJECTIVE: To examine one young female patient with hereditary FVII deficiency and her family members, to observe the gene mutation and clinical phenotype, and to investigate the molecular mechanism of the dysfunction. METHODS: Prothrombin time (PT), activated partial thromoploastin time (APTT), fibrinogen (Fg) and FVII activity (FVII:C) and FVII antigen (FVII:Ag) were tested. The gene mutations were sought by DNA sequencing for all of the exons and flanks, 5' and 3' non-translation region of F7 gene. To confirm the role of the found gene mutation, the reverse sequence were determined with Chromas software. To infer the influence of the mutation on the synthesis and function of FVII protein, the FVII protein molecule model containing the found mutation was constructed and the function prediction was performed by the signal peptide prediction database. RESULTS: Compared with the normal population, the proband's PT value was significantly prolonged, and the ratio % FVII:C and that of FVII:Ag were significantly decreased by 1.1% and 0.9%, respectively. The PT, APTT, FVII:C and FVII:Ag of the proband's parents were both normal. Heterozygous 556th nucleotide mutations T/G were found in the proband's and his father's exon lA of F7 gene, with codon CTG turning into CGG, corresponding leucine (L) into arginine (R), i.e Leu12Arg. Function prediction showed that L12R mutations affected the segmentation of different parts of the signal peptide and its corresponding function, which could result in the decline in the mature protein synthesis and its activity obviously. In addition, a spontaneous 3' untranslated region c11814-insAA heterozygous mutation was detected in the proband's F7 gene, while her parents didn't possess this mutation. CONCLUSION: A new hererozygous mutation (L12R) located in signal peptide of F7 gene is the primary molecular basis of the case with hereditary FVII deficiency. At the same time, the proband's spontaneous 3' non-translation region c11814-insAA mutation may lead to the further reduetion of the FVII synthesis.