Typing of MNSs blood group specific sequences in the human genome and characterization of a restriction fragment tightly linked to S-s- alleles

Human erythrocyte membrane alpha and delta glycophorins (glycophorins A and B) carry the antigens for the M,N,S,s blood group system. Synthetic oligonucleotides spanning coding regions for M,N,S, and s epitopes were used to examine DNAs from 50 individuals selected at random and from individuals known to exhibit S(-)s(-)U- or S(-)s(-)U+ blood group phenotypes. We showed that M,N,S,s, blood group-specific sequences occur as multicopies in the human genome and reside within the alpha and delta glycophorin genes and also within the third glycophorin gene (glycophorin E gene). DNA typing with M- and N-epitope-specific probes showed distinct patterns that allowed correlation of the genotypes with the blood group phenotypes. The correlation using S- and s-specific probes was less definite owing to cross-hybridization. An Mspl restriction fragment length polymorphism (RFLP) residing in the E gene was detected in the black population. This RFLP is also carried by all individuals tested who exhibit the S(-)s(-)U- and S(-)s(-)U+ blood groups phenotypes, thereby serving as a useful marker for the S-s- alleles. The site of cleavage resulting in this RFLP was localized to the second intron of the E gene, and cleavage could occur through differential methylation of its two alleles.