FACTOR-VII MIE - HOMOZYGOUS ASYMPTOMATIC TYPE-I DEFICIENCY CAUSED BY AN AMINO-ACID SUBSTITUTION OF HIS (CAC) FOR ARG(247)(CGC) IN THE CATALYTIC DOMAIN

We found hereditary factor VII deficiency in a clinically asymptomatic family, and characterized their factor W gene and the abnormal molecu le using recombinant DNA techniques. The propositus was a 45-year-old woman who was noted to have a prolonged prothrombin time. The level of factor VII antigen of the patient was 25.9% of that of normal individ uals and the level of factor Vn activity was 28% and 24%, when tested using rabbit brain tissue factor and human placental tissue factor in a one-stage clotting: assay, respectively. Two of her sisters had almo st the same reduced levels of factor VII antigen and activity, and her parents who are first cousins, a son, a daughter and a niece had mode rately reduced leves of both factor VII activity and antigen. To ident ify the mutation site, all the coding exons and exon-intron boundaries of the factor VII gene of the propositus were amplified using the pol ymerase chain reaction (PCR), then subcloned and sequenced. One missen se mutation (G to A) was identified in exon VIII of the gene resulting in an amino acid substitution of His(C ($) under bar AC) for Arg(247) (C ($) under bar GC) in the gene product, PCR using a mutagenic primer to introduce a new ApaL I site into the mutant allele of the patient' s factor VII gene revealed that this allele was inherited in the affec ted individuals in the pedigree. Transient expression assays using BHK cells transfected with an expression vector containing the mutant fac tor VII cDNA suggested that this mutation leads to factor VII deficien cy by impairing secretion of the mutated factor VII. This is the first report of a single point mutation which induces factor VII deficiency with bath activity and antigen reduced in parallel.