Mutations of factor XXXX cleavage sites in @entity447 .

@entity1 @entity462 @entity447 @entity535 @entity797 @entity369
@entity447 is caused by a defect in coagulation factor @entity797 , a protein that undergoes extensive proteolysis during its activation and inactivation. To determine whether some cases of @entity447 are caused by mutations in important cleavage sites, we screened @entity1 DNA samples for mutations in these sites by a two-step process. Regions of interest were amplified from genomic DNA by repeated rounds of primer-directed DNA synthesis. The amplified DNAs were then screened for mutations by discriminant hybridization using oligonucleotide probes. Two cleavage site mutations were found in a survey of 215 @entity1 . A nonsense mutation in the activated protein C cleavage site at @entity535 336 was discovered in a @entity1 with severe @entity447 . In another severely affected @entity1 , a mis-sense mutation results in a substitution of @entity462 for @entity369 in the thrombin activation site at @entity535 1689. This defect is associated with no detectable factor @entity797 activity, but with normal levels of factor @entity797 antigen. The severe @entity447 in this @entity1 was sporadic; analysis of the mother suggested that the mutation originated in her gametes or during her embryogenesis. The results demonstrate that this approach can be used to identify factor @entity797 gene mutations in regions of the molecule known to be important for function.
