Frequency of polymorphisms in the B-domain of factor V gene in APC-resistant patients

In this study we investigated a group of patients in whom a resistance to A PC (activated protein C) was found but no Leiden mutation existed in the pr esence of missense mutations in the first 1200 bp of the Exon 13 (B-domain) in the factor V (FV) gene. The determination of the APC response was perfo rmed using the Immunochrom(R) APC response Test Kit. The mutations were det ermined by temperature gradient gel electrophoresis and DNA sequencing. In the APC-resistant patients without the FV Leiden, we found 4 silent mutatio ns (2298C>T, 2325T>C, 2379A>G, 2391A>G) and 4 missense mutations (2540A>C, 2663A>G, 2684A>G, 2863A>G), which code for the amino acids N789T (GenBank A ccession # AF119360), K830R, H837R, and K897E. In all of the patients and c ontrols, the polymorphisms at nucleotide positions 2391, 2663, 2684, and 28 63 appeared to be associated. In the major allele all bases are A (A allele ) and in the minor allele are G (G allele). A significantly lower G allele frequency was observable in the patient group than in the control group (0. 14 vs. 0,31;p<0.05). The frequency of the 2540C allele, which is associated with the 2379G and the 4070G allele (non-Leiden!), did not differ signific antly between the patient and the control groups (0.17 vs. 0.09; p=0.103). We suggest that the G allele, which is not associated with the FV Leiden mu tation, as well as the [2379G; 2540C; 4070G] allele have no influence on th e APC cofactor function itself, or only subtly as determined in the test sy stems used. (C) 2000 Elsevier Science Ltd. All rights reserved.