OBJECTIVETo identify gene mutations involved in five cases of inherited factor V (FV) deficiency.

METHODSActivity of FV was determined by one-stage clotting assay using FV-deficiency plasma, and FV antigen by an ELISA assay. All the exons and exon-intron boundaries of FV gene were amplified by PCR and then DNA sequencing. Restriction enzyme analysis was used to analyze the probands, their family members and healthy volunteers.

RESULTSBoth activity and antigen of FV in the 5 patients were extremely lower compared with that of normal mixed plasma. Six mutations were identified in these 5 patients, G69969T (G2079V), C45533T (R712Ter), C46796T (R1133Ter), G45366A (C656Y), C46253T (R952C) and G16088C (D68H), the latter three were novel mutations reported for the first time and the C46253T (R952C) was the first missense mutation reported in B domain. The result of sequencing or restriction enzyme analysis showed that the three novel missense mutations were not caused by single nucleotide polymorphisms.

CONCLUSIONGene mutations in 5 type I inherited FV deficiency of patients including 2 nonsense mutations and 4 missense mutations identified which led to the instability of FV protein and the reducing of FV: Ag in the plasma.