A SEQUENCE-ANALYSIS OF VON-WILLEBRAND-FACTOR MESSENGER-RNA, GENE, ANDPSEUDOGENE IN 2 PATIENTS WITH VON-WILLEBRAND DISEASE TYPE 2B, AND AN INVESTIGATION OF GENE CONVERSION IN ITS GENE

We identified the point mutations in two unrelated patients with von W illebrand disease (vWD) type 2B using sequence analyses of the gene, p seudogene and messenger RNA of vWF. Both patients were determined to b e heterozygotes with amino acid transitions of 1308 Arg-->Cys in Case 1 and 1316 Val-->Met in Case 2. Moreover, we also found single base tr ansitions 7541 A-->G in intron 27 of the active gene, and 7642 A-->G, which thus destroyed the Kpn 1 site, in its pseudogene in both cases. Since these mutations represented changes in the base between the gene and its pseudogene, we studied the presence of gene conversion in exo n 28 of vWF gene to clarify its pathological role. Using RT-PCR and an allele-specific restriction enzyme analysis, we identified no gene co nversions in this region in four other patients with VWD, 25 normal su bjects and one cell line, MEGO1. Based on these findings, gene convers ion in the vWF gene is not considered to be a frequent phenomenon in e ither VWD patients or normal subjects.