Characterization of cDNA clones for human glycophorin A

Glycophorin A is the major membrane sialoglycoprotein of human erythrocytes and represents a typical example of a transmembrane glycoprotein. The functional role of this cell‐surface component is not known but it represents a receptor for viruses, bacteria and parasites like Plasmodium falciparum.1 Two cDNA clones encoding glycophorin A have been characterized from human fetal cDNA libraries. The longer cDNA extended from the coding region of glycophorin A (residues 4–131) to the 3′ untranslated region which included two polyadenylation signals and a poly(A) tail. 2 The structural gene for glycophorin A is located on chromosome 4, q28–q31 as shown by in situ hybridization, thus confirming the previous localization by genetic linkage analysis. 3 Three distinct mRNA species (1.0 kb, 1.7 kb and 2.2 kb) have been identified in erythroid spleen. Northern blot analyses with a probe directed against the 3′ untranslated region of the mRNAs indicated that all these species share a homologous 3′ non‐coding region and that the first polyadenylation signal downstream the stop codon is not used. 4 Preliminary studies by Southern blot analysis of the genomic DNA from normal En(a+) and rare En(a‐) donors suggest that the glycophorin A gene has a complex organization and is largely deleted in donors of the En(a‐) phenotype (Finnish type) who lack glycophorin A on their red cells.