New alleles of the platelet glycoprotein Ibalpha gene

Platelet membrane glycoprotein Ibalpha (GP Ibalpha) bears two molecular polymorphisms which are in linkage disequilibrium: the C/T dimorphism at codon 145 (HPA-2) and the variable number of tandem repeats (VNTR) polymorphism in the macroglycopeptide region. The frequencies of these two polymorphisms, and of another three recently described silent polymorphisms, were investigated by genotypic identification in 729 Caucasian individuals from the south of Spain. Eight different alleles of this gene, including the longest VNTR A allele of the GP Ibalpha gene, were found in this population. Moreover, we detected an unexpected linkage between the B and A variants of the VNTR polymorphism and the HPA-2a allele in 5.9% of this population. These results suggest a new evolutionary model of GP Ibalpha, in which homologous recombination could account for the genetic diversity of the GP Ibalpha.