M. Alan Chester

A Rapid and Simple ABO Genotype Screening Method Using a Novel B/O2 versus A/O2 Discriminating Nucleotide Substitution at the ABO Locus

An ABO genotype screening method discriminating the common alleles A1, A2, B, O1 and O2 at the ABO locus was made possible by the discovery of a novel nucleotide substitution (G1096A) present only in B and O2 alleles. A rapid and reliable single‐tube approach using multiplex PCR with four primers amplifying exons 6 and 7 of the ABO genes followed by simultaneous addition of two restriction enzymes was developed and validated in a population of 150 Swedish blood donors. This technique is the most cost‐efficient and informative ABO genotyping method reported to date.

Frequent occurrence of a variant O1 gene at the blood group ABO locus

Blood group ABO polymorphism was analysed in genomic DNA isolated from 150 blood donors by restriction endonuclease digestion of three polymerase chain reaction‐amplified exons in the ABO genes and by sequencing of randomly selected samples. An anomalous O1 allele first described in a cancer cell line is now shown to account for approximately 40% of the O alleles described to date. This is 10 times more frequent than the only other known variant O allele (O2). This variant O1 allele has at least seven point mutations when compared to the consensus gene, in addition to the deletion characterising the normal O1 allele.

ABO exon and intron analysis in individuals with the AweakB phenotype reveals a novel O1v-A2 hybrid allele that causes four missense mutations in the A transferase

BackgroundSince the cloning in 1990 of cDNA corresponding to mRNA transcribed at the blood-group ABO locus, polymorphisms due to ethnic and/or phenotypic variations have been reported. Some subgroups have been explained at the molecular level, but unresolved samples are frequently encountered in the reference laboratory.ResultsABO blood grouping discrepancies were investigated serologically and by ABO genotyping [duplex polymerase-chain-reaction (PCR) – restriction-fragment-length-polymorphism (RFLP) and PCR – allele-specific-primer (ASP) across intron 6] and DNA sequencing of the ABO gene and its proposed regulatory elements. Blood samples from five individuals living in Portugal, Switzerland, Sweden and the USA were analysed. These individuals were confirmed to be of Black ethnic origin and had the unusual AweakB phenotype but appeared to have the A2B genotype without previously reported mutations associated with weak A or B expression. Sequencing of this A allele (having 467C>T and 1061delC associated with the common A2 [A201] allele) revealed three mutations regularly encountered in the O1v[O02] allele: 106C>T (Val36Phe), 188G>A (Arg63His), 220C>T (Pro74Ser) in exons 3, 4 and 5, respectively. The additional presence of 46G>A (Ala16Thr) was noted, whilst 189C>T that normally accompanies 188G>A in O1vwas missing, as were all O1v-related mutations in exons 6 and 7 (261delG, 297A>G, 646T>A, 681G>A, 771C>T and 829G>A). On screening other samples, 46G>A was absent, but two new O alleles were found, a Jordanian O1 and an African O1vallele having 188G>A but lacking 189C>T. Sequencing of introns 2, 3, 4 and 5 in common alleles (A1 [A101], A2, B [B101], O1, O1vand O2 [O03]) revealed 7, 12, 17 and 8 polymorphic positions, respectively, suggesting that alleles could be defined by intronic sequences. These polymorphic sites allowed definition of a breakpoint in intron 5 where the O1v-related sequence was fused with A2 to form the new hybrid. Intron 6 has previously been sequenced. Four new mutations were detected in the hybrid allele and these were subsequently also found in intron 6 of A2 alleles in other Black African samples.ConclusionsA novel O1v-A2 hybrid was defined by ABO exon/intron analysis in five unrelated individuals of African descent with the AweakB blood group phenotype.

New and unusual O alleles at the ABO locus are implicated in unexpected blood group phenotypes.

BACKGROUND:  In the ABO blood group system mutations in the A gene may lead to weak A subgroups owing to a dysfunctional 3‐α‐N‐acetylgalactosaminyltransferase.

Oligosaccharides from feces of preterm infants fed on breast milk

Nine neutral and five acidic oligosaccharides were isolated from feces of a preterm (30th postmenstrual week) blood group A nonsecretor infant fed on pooled breast milk. Structural analyses were carried out using sugar and methylation analyses, fast atom bombardment mass spectrometry, and 1H NMR. The acidic oligosaccharides are well-known components of human milk. The neutral oligosaccharides are characteristic of nonsecretor milk. Surprisingly, no secretor gene-dependent oligosaccharides were present in the feces. Another preterm (27th postmenstrual week) blood group A, secretor infant fed on pooled breast milk showed the same fecal oligosaccharide pattern as above during the first week after birth, despite being a secretor individual. Also notable was the absence of blood group A-active oligosaccharides in this sample. Another sample of feces collected 8 weeks later from the latter infant contained the expected blood group A-active oligosaccharides. Furthermore, free sialic acid was present at the cost of the sialyl oligosaccharides seen earlier. Thus, infants born prematurely do not show the same degree of development of oligosaccharide metabolism as their more mature counterparts.

Evidence for a new type of O allele at the ABO locus, due to a combination of the A2 nucleotide deletion and the Ael nucleotide insertion

Using a recently introduced multiplex polymerase chain reaction and restriction fragment length polymorphism ABO genotype screening method we have found an anomalous ABO genotype (A2O1 variant) not correlating with the serological phenotype (blood group O). The blood group was confirmed by absorption/elution and detection of blood group substances in saliva. Sequencing of exons 6 and 7 in the ABO genes of the propositus indicated an A2 gene (C467T and C1060‐) apparently inactivated by the same single nucleotide insertion recently reported in individuals with the ABO subgroup Ael. Investigation of relatives confirmed the inheritance of this new inactive hybrid allele.

Urinary excretion of a glucose-containing tetrasaccharide. A parameter for increased degradation of glycogen

The urinary excretion of a glucose-containing oligosaccharide, Glc alpha[1-6Glc alpha[1-4Glc alpha[1-4Glc, (Glc4) has been measured in various physiological and pathological conditions. The Glc4 content of 24 h samples from the same individual was relatively constant, whereas 2 h samples showed up to 4-fold variations in Glc4 concentration. This variation is associated mainly with increased excretion of Glc4 after meals. A carbohydrate-rich diet, starvation or a protein-rich diet, and intense physical activity all affected the urinary excretion of Glc4. Both oral and intravenous administration of glycogen in a Rhesus monkey resulted in increased excretion of Glc4. When Glc4 itself was injected intravenously in small amounts renal clearance was rapid and complete. In contrast, injection of a larger amount resulted in incomplete (approximately 10%) renal clearance, probably due to uptake and metabolism of the oligosaccharide. In patients with glycogen storage diseases, certain malignancies, and pancreatitis, 24 h urinary Glc4 excretion exceeded the normal range. The diagnostic implications of these observations deserve evaluation. The results presented suggest a need for standardization of nutritional status and physical activity when monitoring urinary Glc4 excretion for diagnostic purposes.

ABO transcript levels in peripheral blood and erythropoietic culture show different allele-related patterns independent of the CBF/NF-Y enhancer motif and multiple novel allele-specific variations in the 5'- and 3'-noncoding regions.

BACKGROUND: Mechanisms regulating the ABO gene are unclear, especially in the hematopoietic compartment. The number of 43‐bp repeats in the CBF/NF‐Y‐binding enhancer region is considered to have a major influence on transcription.

Different genotypes causing indiscernible patterns of A expression on A(el) red blood cells as visualized by scanning immunogold electron microscopy

Background and Objectives: The published sequence of the weak A subgroup Ael gene from Swedish individuals showed a G insertion in exon VII, causing a frameshift at codon 268 (the A1 gene has 353 codons). We wished to sequence exons VI and VII of two Norwegian Ael individuals and compare the expression of A substance on RBC from different Ael individuals. Materials and Methods: Exon VI and VII were amplified by PCR, cloned in M13 and sequenced. A structure expression on Ael RBC was studied by the immunogold technique. Results: In contrast to the Swedish Ael individuals, the two Norwegians had consensus A1 sequences in exon VI and VII. However, the patterns of A expression were indiscernible from the Swedish cases as visualized by immunogold labeling in SEM. In both cases, a few (1–2%) RBC were very strongly labeled, some were weakly labeled and the majority (95%) were unlabeled. Conclusion: Although some Ael individuals have an inserted nucleotide in exon VII of the ABO gene, others have consensus A1 sequence in exon VI and VII. However, we could not find any differences in phenotype by immunogold labeling in SEM.

Structural basis for red cell phenotypic changes in newly identified, naturally occurring subgroup mutants of the human blood group B glycosyltransferase.

BACKGROUND: Four amino‐acid‐changing polymorphisms differentiate the blood group A and B alleles. Multiple missense mutations are associated with weak expression of A and B antigens but the structural changes causing subgroups have not been studied.