The short tandem repeat locus VWF2 in intron 40 of the von Willebrand factor gene consists of two polymorphic sub-loci

This study describes the complex nucleotide sequence structure of the TCTA short tandem repeat (STR) locus, VWF2. Eight alleles of VWF2 were observed in a population of 116 unrelated Caucasian individuals. The alleles ranged in size from 150 to 178 base pairs (bp). Sequence analysis of the isolated alleles revealed two polymorphic regions that were named subloci VWF2-a and VWF2-b. VWF2-a is located at the 5 ' end of the conventional locus, whilst VWF2-b is located at the 3 ' end. The two sub-loci are joined by a 30-nucl eotide non-polymorphic sequence which contains two additional TCTA motif re peats. A semi-nested polymerase chain reaction (PCR) was designed to amplif y the VWF2-b region in conjunction with the standard VWF2 amplification. Th is new amplification method enabled a higher level of allele discrimination than could be achieved by assigning alleles according to size. A cohort of 99 unrelated individuals was tested with this method. VWF2-a expressed fiv e different alleles ranging from zero motif repeats to four motif repeats, while VWF2-b alleles ranged from 8 to 14 motif repeats. Allelic configurati on based on the VWF2-a and VWF2-b sub-alleles revealed 23 unique configurat ions out of a possible 31 for the original eight VWF2 alleles. In conclusio n, the VWF2 is a highly polymorphic STR locus with potential application fo r forensic and parentage testing. (C) 2001 Elsevier Science Ireland Ltd. Al l rights reserved.