ABSTRACT
Severe coagulant factor VII (FVII) deficiency in postpubertal dizygotic twin males results from two point mutations in the FVII gene, a promoter region TâC transition at -60 and a His-to-Arg substitution at amino acid 348; both mutations prevent persistence of plasma functional FVII. This report documents longitudinal laboratory measurements from infancy to adulthood of FVII coagulant activity (FVII:C) in the twin FVII-deficient patients; it also details specific biochemical analyses of the -60 TâC mutation. The results revealed FVII:C levels of less than 1% in infancy that remain severely decreased through puberty and into adulthood. In-vitro analyses utilizing hepatocyte nuclear factor 4α (HNF4α) co-transfection and a chromatin immunoprecipitation assay indicate that the -60 TâC mutation severely diminishes functional interaction between the FVII promoter and transcription factor HNF4α. The importance of interaction between the FVII gene and HNF4α in normal FVII expression provides an in-vivo illustration of the regulated expression of an autosomal gene encoding a coagulation protein. The constancy of FVII:C and peripubertal patient symptomatology reported here illustrates androgen-independent expression in contrast to expression with an analogous mutation in the promoter region of the gene encoding coagulation FIX.
Subject(s)
Factor VII Deficiency/genetics , Factor VII/genetics , Hepatocyte Nuclear Factor 4/metabolism , Point Mutation , Promoter Regions, Genetic , Adult , Base Sequence , Binding Sites/genetics , Child, Preschool , DNA Mutational Analysis , Factor VII/chemistry , Factor VII/metabolism , Factor VII Deficiency/blood , HeLa Cells , Hep G2 Cells , Hepatocyte Nuclear Factor 4/genetics , Humans , Immunoprecipitation , Longitudinal Studies , Male , Plasmids , Protein Binding/genetics , Transfection , Twins, DizygoticABSTRACT
African Americans with factor VII (FVII) deficiency, as defined by clinical laboratory values, are frequently asymptomatic. To date the genotypes underlying this FVII defect in asymptomatic African Americans have not been established. We show in 3 unrelated African-American patients that the defect is due to a G to A nucleotide change resulting in an arginine to glutamine mutation in Factor VII amino acid 304. This defect results in low FVII coagulant activity levels using rabbit brain thromboplastin but not using human thromboplastin. This report may aid transfusion and hematology specialists evaluate patient results and prevent unnecessary transfusions to treat patients with abnormal laboratory values.
