Two novel type 2N von Willebrand disease-causing mutations that result in defective factor VIII binding, multimerization, and secretion of von Willebrand factor

Two novel mutations, a T-to-C transition at nucleotide 2612 and a T-to-G tr ansversion at nucleotide 3923 of the von Willebrand factor (VWF) complement ary DNA, were detected by analysis of the vWF gene in DNA from members of 2 families with atypical von Willebrand disease. The T2612C transition predi cts substitution of cysteine by arginine at amino acid position 788 (C788R) , and the T3923G transversion predicts substitution of cysteine by glycine at position 1225 (C1225G) of pre-pro-vWF, The patients homozygous for the C 788R and C1225G mutations both had a partial VWF deficiency (0.18 IU/mL and 0.07 IU/mL vWF antigen, respectively); VWF in plasma from patients homozyg ous for either the C788R or the C1225G; mutation failed to bind factor VIII and lacked high molecular weight multimers, Recombinant (r) VWF molecules having the C788R or C1225G mutation were expressed In COS-7 cells. Both rvW F C788R and rvWF C1225G exhibited significantly impaired secretion and fail ed to bind factor VIII, Recombinant VWF C788R in COS-7 culture medium showe d a severe reduction in high molecular weight multimers, whereas rvWF C1225 G showed a very mild reduction in high molecular weight multimers when comp ared with wild-type rrWF. (C) 2000 by The American Society of Hematology.