A Rare Variant <i>c.1024A&gt;C</i> in the <i>ABO*A1.02</i> Allele Was Associated with an A_el Phenotype

Abstract

<b><i>Introduction:</i></b> A_el is known to be one of the weakest A subgroups and can be identified through either the adsorption-elution technique or molecular analysis. Single nucleotide variation in the <i>ABO</i> gene can potentially disrupt the function of ABO glycosyltransferase, resulting in decreased ABO antigen expression. <b><i>Case Presentation:</i></b> We reported 1 case of the missense SNV <i>c.1024A&gt;C</i> in the <i>ABO*A1.02</i> allele was associated with an A_el phenotype. The proband was a 19-year-old male Chinese Han blood donor who was initially stereotyped as type B. Based on the findings from absorption elution, genotype tests, and a family investigation, both the proband and his mother were classified as the A_elB phenotype. An uncommon allele was detected in both the proband and his mother, differing by a single nucleotide at position 1,024 from A to C (<i>c.1024A&gt;C</i>) when compared to the <i>ABO*A1.02</i> allele. The <i>c.1024A&gt;C</i> SNV induces an amino acid substitution, specifically p.Thr342Pro, which consequently leads to the loss of two sheets (p214–p216, p340–p344) in the wild-type A glycosyltransferase (GTA) 3D structure. The removal of these two sheets, situated at the protein’s core, implies the occurrence of an interaction within this domain that affects the stability of the protein structure. <b><i>Conclusion:</i></b> A_elB is prone to misidentification as type B, and the accurate determination of blood type can be achieved through the integration of the adsorption-elution technique and molecular analysis.