IMMUNOHEMATOLOGY: A novel cis-AB allele derived from a unique 796C>A mutation in exon 7 of ABO gene

• Published in: Transfusion (Philadelphia, Pa.) Pa.), 2005-01, Vol.45 (1), p.50-55
• Main Authors: Tzeng, Cheng-Hwai, Chen, Ying-Ju, Lyou, Jau-Yi, Chen, Pei-Shan, Liu, Hsueng-Mei, Hu, Hui-Yu, Lin, Jeong-Shi, Yu, Lung-Chih
• Format: Article
• Language: English
• ISSN: 0041-1132; 1537-2995
• DOI: 10.1111/j.1537-2995.2005.04108.x

BACKGROUND:The cis-AB phenotype is very rare, and only three genotypes that correspond to specific ABO allele changes have been reported. Cis-AB01 involves the A102 allele with a nonsynonymous substitution G803C in exon 7, whereas cis-AB02 and cis-AB03 involve different nonsynonymous substitutions A796C and C700T, respectively, on the B101 allele background. The nucleotide substitutions give rise to a change of the respective glycosyltransferase, resulting in varying bifunctional AB transferase activities. STUDY DESIGN AND METHODS:Two cis-AB phenotypes were identified in a Taiwanese C. family and two unrelated individuals, respectively. Serologic studies, molecular cloning, and sequencing of exon 6 and exon 7 were carried out to determine their respective phenotypic characteristics and cis-AB alleles. A cohort of 300 AB-phenotype, healthy random individuals served as controls. RESULTS:A novel cis-AB allele is uncovered out of the three family members, of which a 796C>A substitution occurs predicting an amino acid change at residue 266 of leucine to methionine on the background of A102 allele. It is serologically like cis-AB03, an A sub(2)B phenotype, but molecularly different. Both of the two unrelated individuals are of cis-AB01 allele, and all of the 300 AB blood group controls are excluded cis-AB phenotype. CONCLUSION:The C. family described carries a novel cis-AB allele that differs molecularly from all previously reported cis-AB alleles.