Serological and Biochemical Investigations on the N.E. Variety of the Dantu Red Cell Phenotype. In: Brinkmann B, Henningsen K, editors. 11th Congress of the Society for Forensic Haemogenetics (Gesellschaft für forensische Blutgruppenkunde e.V.). Berlin: Springer Berlin Heidelberg; 1986. pp. 3-7. [DOI: 10.1007/978-3-642-71150-3_1]

Molecular analysis of glycophorin A and B gene structure and expression in homozygous Miltenberger class V (Mi. V) human erythrocytes

In the Miltenberger class V (Mi. V) condition, red cells lack glycophorin A (GPA) and glycophorin B (GPB) but carry instead an unusual glycoprotein thought to be a hybrid molecule produced by the unequal crossing-over between the closely linked genes encoding for GPA and GPB. By Western blot analysis with rabbit anti-GPA antibodies specific for discrete domains of GPA, it was found that the Mi. V glycoprotein (donor F. M.) contains approximately 60 amino acid residues of GPA at its N-terminus. As a preliminary approach to the molecular analysis of this variant the restriction maps of the GPA and GPB genes were established by Southern blot analysis of genomic DNA and from genomic clones isolated from a human leukocyte library constructed in lambda EMBL4. The GPA and GPB genes cover about 30 kb of DNA and are organized into seven exons (A-1-A-7) and five exons (B-1-B-5), respectively. In addition to the normal genes, a third gene (named inv), closely resembling the GPA and GPB genes, was also identified. In the homozygous Mi. V individual the normal GPA and GPB genes were absent, but an unusual form of gene structure was detected by Southern blot analysis. The Mi. V glycoprotein gene was composed of exon B-1 of the GPB gene followed by exons A-2 and A-3 of the GPA gene and the exons B-3, B-4 and B-5 of the GPB gene. Exon B-1 can be distinguished from exon A-1 of GPA since it is located within a different restriction fragment, but both encode the same amino acid sequence (N-terminal region of the signal peptides). Using the polymerase chain reaction, the junction between exon A-3 and exon B-3 was confirmed by amplification of the DNA region where the putative crossing-over has occurred and it was deduced that the Mi. V glycoprotein is a hybrid molecule composed of amino acid residues 1-58 from GPA fused to amino acid residues 27-72 of GPB. In addition, the finding that part of the signal peptide and the 5'-untranslated region are derived from GPB suggests that the genetic background of the Mi. V variant is rather complex and may involve a cascade of recombination or gene conversion events.

Hybrid glycophorins from human erythrocyte membranes. I. Isolation and complete structural analysis of the hybrid sialoglycoprotein from Dantu-positive red cells of the N.E. variety

The hybrid glycophorin in Dantu-positive human erythrocytes of the N.E. variety was not cleaved by treatment of intact cells with various proteases, in contrast to normal glycophorins. Therefore, it could be purified by phenol/saline extraction of membranes from trypsin-treated and chymotrypsin-treated red cells and subsequent gel filtration in the presence of Ammonyx-LO. The complete structure of the hybrid molecule, comprising 99 amino acid residues, was elucidated by sequence analyses of peptides prepared by chymotrypsin, trypsin, cyanogen bromide or V8 proteinase treatment. The N-terminal 39 residues and the glycosylation of the molecule were found to be indistinguishable from those of blood-group-s-specific glycophorin B. Conversely, the residues 39-99 were shown to be identical with the residues 71-131 of the major blood-group M-active or N-active sialoglycoprotein (glycophorin A). Hemagglutination inhibition assays revealed that the Dantu antigen represents a labile structure. The receptor might be located within the residues approximately 28-40 of the hybrid glycophorin, as judged from the effects of modifications of membranes. Our data provide an explanation for the previous findings that Dantu-positive cells (N.E. type) exhibit a protease-resistant N antigen and a qualitatively altered s antigen.