A Novel A(superscript el) Allele Derived from a Unique 816insG in Exon 7 of the ABO Gene

Abstract

The ABO blood group system is the most important blood group system in transfusion medicine. In addition to the major A, B and O alleles, many rare alleles with weak expression of the A or B antigens on RBCs have been defined. We report here the molecular analysis of a novel A(superscript el) allele. Exons 6 and 7 of the ABO gene were PCR-amplified, cloned and sequenced for the propositus, Mr C, who is a 56-year-old Taiwanese male and was incidentally observed to have an A(superscript el) phenotype. His direct family members including wife, son and daughter were subsequently enrolled for further study. Three hundred random blood donors of AB phenotype served as control. A novel A(superscript el) allele was uncovered from the propositus and his daughter, of which a unique 816insG mutation occurred on the A102 background that results in a frame shift leading to a 37-amino acid longer polypeptide than the normal A1 transferase, a finding similar to that of Ael01 allele with 804insG. We found that the C family carried a novel A(superscript el) allele that differs molecularly from seven A(superscript el) alleles reported in the literature.