Molecular heterogeneity of the A₃subgroup

Abstract

The molecular characterization of the subgroup A3 remains unclear. Four unrelated A3 blood donors were studied. Family studies were possible in three of them. The A3 subgroup was defined by immunohaematological evaluation with four different commercially available serums. Exons VI and VII of the ABO gene, responsible for 91% of the catalytic active part of the glycosyltransferase, were amplified and subjected to direct sequencing. The results in all samples showed heterozygosity for the G261 deletion. In the A3 allele, the following associations were found: C467T mutation and 1060C deletion in one A3 blood donor and in another G829A and 1060C. In one case, only the 1060C deletion was demonstrated in the A3 allele. One blood donor presented the T646A and the G829A mutations in homozygosity. It was concluded that the A3 blood group is very heterogeneous at the molecular level.

Many genetically defined ABO subgroups exhibit characteristic flow cytometric patterns

“…The latter finding rules out a chimeric state as well as transfusion as the cause of ABO discrepancy in these cases. Even if there have been reports describing mutations associated with A 3 , 34,50 we consider the genetic basis of the original A 3 phenotype to be unresolved. Certainly, in the Nordic countries, where the frequency in Denmark has been reported at 1 in 1000, 51 our findings contradict that of the first reported A 3 sample for which the molecular background was determined 34 .…”

A unique 502C>T mutation in exon 7 of ABO gene associated with the Bel phenotype in Taiwan

“…Since the genomic basis of the glycosyltransferase gene was first cloned and unveiled in 1990, 2,3 a number of variant A or B alleles have been characterized in those individuals 10‐13 . In addition, genetic heterogeneity has been found among distinct ABO subgroups.…”

Genomic analysis of clinical samples with serologic ABO blood grouping discrepancies: identification of 15 novel A and B subgroup alleles

“…[7][8][9][10] Only one or 2 individuals with each phenotypic variant were investigated by sequencing of exons 6 and 7 in the ABO gene. Investigation of other subgroup alleles followed, [11][12][13][14][15] but several examples exist in which no deviation from the consensus sequence was found in exons 6 and 7. 7,15,16 In total, 8 A (including cis-AB) and 6 B subgroup [including 2 B(A)] alleles defined by missense mutations in exon 7 have been described to date.…”