Immunochemical properties of Mg erythrocytes

Molecular characterization of glycophorin A transcripts in human erythroid cells using RT-PCR, allele-specific restriction, and sequencing

Glycophorin A (GPA) is an erythroid-lineage-specific membrane sialoglycoprotein which occurs in two allelic forms, M and N, which form the antigens of the MN blood group. Purified cDNAs and RNAs isolated from peripheral blood and erythroleukemia cell lines, HEL and K562, were used to develop an RT-PCR technique for amplifying GPA gene transcripts (GYPA). The relative expression of transcripts from the M and N alleles was determined using restriction analysis of these amplified products with four allele-specific restriction endonucleases. The use of this method permits the sensitive identification of GYPA transcripts in these cells and confirms GPA protein expression in the erythroleukemia cell lines and the MN phenotypes of individuals determined by immunolabeling with GPA allele-specific monoclonal antibodies. A novel restriction pattern was obtained using peripheral blood RNA from two individuals with a rare inherited variant allele, GPA Mg. Sequencing of the cDNA obtained using this method revealed a single C to A transversion in the fourth codon in the mature GYPA N coding sequence is responsible for the difference between GYPA Mg and GYPA N.

An unusual sialoglycoprotein associated with the Webb-positive phenotype

This paper presents the results of a study on the erythrocyte membrane proteins from Webb-positive individuals. The membrane proteins were separated by polyacrylamide electrophoresis and stained using a Silver stain as well as Coomassie blue and PAS stains. All Webb-positive individuals exhibited a decrease in the beta-sialoglycoprotein beta SGP band along with the appearance of a new SGP 3,000 daltons less than beta SGP. It is postulated that this band is an abnormal beta SGP possibly lacking the N-linked oligosaccharide that is normally present in beta-SGP.