Novel hybrid genes and a splice site mutation encoding the Sta antigen among Japanese blood donors

BACKGROUND

The low-incidence antigen St^a of the MNS system is usually associated with the GP(B-A) hybrid molecule, which carries the 'N' antigen at the N terminus. The GP(A-A) molecule with trypsin-resistant M antigen has been found in a few St(a+) individuals.

MATERIALS AND METHODS

Among Japanese blood donors, we screened 24 292 individuals for the presence of St(a+) with trypsin-resistant 'N' antigen and 193 009 individuals for the presence of St(a+) with trypsin-resistant M antigen. The breakpoints responsible for the St^a antigen were analysed by sequencing the genomic DNAs.

RESULTS

A total of 1001 (4·1%) individuals were identified as St(a+) with trypsin-resistant 'N' antigen. Out of 1001 individuals, 115 were selected randomly for sequencing. Two novel GYP*Sch (GYP*401) variants with new intron 3 breakpoints of GYPA were detected in three cases. Twenty-five (0·013%) individuals were identified as St(a+) with trypsin-resistant M antigen. Five individuals had the GYP(A-ψB-A) hybrid allele; two of these five individuals were GYP*Zan (GYP*101.01), and the remaining three had a novel GYP(A-ψB-A) allele with the first breakpoint in GYPA exon A3 between c.178 and c.203. Nine individuals had a novel GYP(A-E-A) allele with GYPE exon E2 and pseudoexon E3 instead of GYPA exon A2 and A3. The 11 remaining individuals had a novel GYP(A-A) allele with a 9-bp deletion that included the donor splice site of intron 3 of GYPA.

CONCLUSION

Our finding on diversity of glycophorin genes responsible for St^a antigen provides evidence for further complexity in the MNS system.

The MNS glycophorin variant GP.Mur affects differential erythroid expression of Rh/RhAG transcripts

BACKGROUND

The band 3 macrocomplex (also known as the ankyrin-associated complex) on the red cell membrane comprises two interacting subcomplexes: a band 3/glycophorin A subcomplex, and a Rh/RhAG subcomplex. Glycophorin B (GPB) is a component of the Rh/RhAG subcomplex that is also structurally associated with glycophorin A (GPA). Expression of glycophorin B-A-B hybrid GP.Mur enhances band 3 expression and is associated with lower levels of Rh-associated glycoprotein (RhAG) and Rh polypeptides. The goal of this study was to determine whether GP.Mur influenced erythroid Rh/RhAG expression at the transcript level.

MATERIALS AND METHODS

GP.Mur was serologically determined in healthy participants from Taitung County, Taiwan. RNA was extracted from the reticulocyte-enriched fraction of peripheral blood, followed by reverse transcription and quantitative PCR for RhAG, RhD and RhCcEe.

RESULTS

Quantification by real-time PCR revealed significantly fewer RhAG and RhCcEe transcripts in the reticulocytes from subjects with homozygous GYP*Mur. Independent from GYP.Mur, both RhAG and RhD transcript levels were threefold or higher than that of RhCcEe. Also, in GYP.Mur and the control samples alike, direct quantitative associations were observed between the transcript levels of RhAG and RhD, but not between that of RhAG and RhCcEe.

CONCLUSION

Erythroid RhD and RhCcEe were differentially expressed at the transcript levels, which could be related to their different degrees of interaction or sensitivity to RhAG. Further, the reduction or absence of glycophorin B in GYP.Mur erythroid cells affected transcript expressions of RhAG and RhCcEe. Thus, GPB and GP.Mur differentially influenced Rh/RhAG expressions prior to protein translation.

Dissecting alternative splicing in the formation of Miltenberger glycophorin subtype III (GYP.Mur)

BACKGROUND AND OBJECTIVES

Miltenberger subtype III (Mi.III, GP.Mur) is one of the most important red cell phenotypes in the fields of transfusion in South-East Asia. GP.Mur is believed to evolve from homologous gene recombination events between glycophorin A (GYPA) and glycophorin B (GYPB). GYP.Mur differs from GYPB in only seven nucleotides dispersed near the region of 3' exon 3 of GYP.Mur. The goal of this study was to dissect how these nucleotide variants affected splicing of exon 3.

MATERIALS AND METHODS

We first designed two minigene constructs: one containing GYP.Mur from exon 2 to exon 4 and the other containing GYPB in the same region. To test how these nucleotide variations between GYP.Mur and GYPB affected the splicing, a repertoire of the GYP.Mur-like minigene constructs with different point mutations were created. These minigene variants were evaluated for their abilities to induce splicing of exon 3 using a heterologous expression system.

RESULTS

(1) GYP.Mur minigene expressed exons 2, 3 and 4, whereas GYPB minigene expressed only exon 2 and exon 4. (2) The single nucleotide alteration at the position of the 5' splice site of glycophorin intron 3 reversed the splicing decision. (3) The nucleotide variations between GYP.Mur and GYPB other than that at the 5' splice site showed very little or no effect on splicing of exon 3.

CONCLUSION

Splicing of the glycophorin B-A-B hybrids (GYP.Mur and GYP.BUN) and unsplicing of GYPB follow the GU-AG rule strictly.

Spectrins: a structural platform for stabilization and activation of membrane channels, receptors and transporters

This review focuses on structure and functions of spectrin as a major component of the membrane skeleton. Recent advances on spectrin function as an interface for signal transduction mediation and a number of data concerning interaction of spectrin with membrane channels, adhesion molecules, receptors and transporters draw a picture of multifaceted protein. Here, we attempted to show the current depiction of multitask role of spectrin in cell physiology. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.