New alleles of the platelet glycoprotein Ib alpha gene

Platelet membrane glycoprotein Ib alpha (GP Ib alpha) bears two molecular p olymorphisms which are in linkage disequilibrium: the C/T dimorphism at cod on 145 (HPA-2) and the variable number of tandem repeats (VNTR) polymorphis m in the macroglycopeptide region, The frequencies of these two polymorphis ms, and of another three recently described silent polymorphisms, were inve stigated 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 Iba 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 resul ts suggest a new evolutionary model of GP Ib alpha, in which homologous rec ombination could account for the genetic diversity of the GP Ib alpha.