Chromosomal localization of the genes for the vitronectin and fibronectin receptors α subunits and for platelet glycoproteins IIb and IIIa

Abstract

The integrins, a family of related membrane receptors involved in cell-cell and cell-matrix interactions, are heterodimeric complexes of α and β subunits. To begin to understand the evolution of these complexes, we studied the genomic organization of several α and β integrin subunits. Using both somatic cell hybrids and an in situ hybridization technique, we have determined the chromosomal location of the genes for the α subunits of the vitronectin receptor (VNR(α)), the fibronectin receptor (FNR(α)), and for the α subunit of the platelet glycoprotein IIb/IIIa complex, GPIIb. In addition, we have determined the chromosomal location of the gene for the β subunit of the GPIIb/IIIa heterodimer, GPIIIa. Our studies indicate that the α subunits do not localize to a single locus, but that each is found on a different chromosome. The gene for VNR(α) is located on chromosome 2, the gene for FNR(α) is on chromosome 12q11 → 13, and the gene for GPIIb is on chromosome 17q21 → 23. In contrast to the chromosomal dispersion of the α subunits, the genes for GPIIb and GPIIIa are physically close, with the gene for GPIIIa also located on chromosome 17q21 → 23. These studies indicate that the genes for the α subunits of the integrin family have been dispersed during evolution while GPIIb and GPIIIa are in close physical proximity. This physical proximity of GPIIb and GPIIIa may be involved in the concurrent expression of these proteins by megakaryocytes, and may result in linkage disequilibrium between these two genes, which would limit the use of restriction length polymorphisms in linkage studies of GPIIb/IIIa abnormalities in small kindreds.