New ABO intron 1 variant alleles

• Published in: Immunohematology Vol. 37; no. 4; p. 178
• Main Authors: Fennell, K, Keller, M A, Villa, M A, Paccapelo, C, Kucerakova, M, Rosochova, J, Clemente DosSantos, C, Brackney, L, Lee, C J, Metcalf, R, Crovetti, G, Barbieri, M, Travali, S, Barrotta, G, Giuca, G, Guerra, L E, Ochoa-Garay, G
• Format: Journal Article
• Language: English
• Published: United States 01.01.2021
• Subjects: ABO Blood-Group System - genetics; Alleles; Humans; Introns; Mutation; Phenotype
• ISSN: 0894-203X
• DOI: 10.21307/immunohematology-2021-029

Unusual and discrepant ABO phenotypes are often due to genetic variants that lead to altered levels or activity of ABO transferases and consequently to altered expression of ABO antigens. This report describes eight genetic alterations found in 15 cases with reduced or undetectable expression of ABO antigens. Forward and reverse ABO grouping was performed by standard gel or tube methods. Adsorption-heat elution and saliva testing for H and A substances followed the AABB technical manual procedures. Genomic DNA extracted from whole blood was PCR-amplified to cover the entire coding sequence, splice junctions, proximal promoter, and intron 1 enhancer. Amplification products were sequenced by next-generation or Sanger dideoxy methods, either directly or after cloning into a bacterial plasmid vector. Eight unreported alleles were found in the 15 cases analyzed. Alleles and harbor variants that alter the consensus sequence at the intron 1 donor and acceptor splice sites, respectively. The other alleles harbor variants that alter the consensus sequence at transcription factor-binding sites in the intron 1 enhancer: specifically, , and at GATA-1 sites; and at a RUNX1 site; and at or near a C/EBP site. Molecular and serologic characterization of alleles can help in their future identification and in the resolution of discrepancies. Unusual and discrepant ABO phenotypes are often due to genetic variants that lead to altered levels or activity of ABO transferases and consequently to altered expression of ABO antigens. This report describes eight genetic alterations found in 15 cases with reduced or undetectable expression of ABO antigens. Forward and reverse ABO grouping was performed by standard gel or tube methods. Adsorption-heat elution and saliva testing for H and A substances followed the AABB technical manual procedures. Genomic DNA extracted from whole blood was PCR-amplified to cover the entire coding sequence, splice junctions, proximal promoter, and intron 1 enhancer. Amplification products were sequenced by next-generation or Sanger dideoxy methods, either directly or after cloning into a bacterial plasmid vector. Eight unreported alleles were found in the 15 cases analyzed. Alleles and harbor variants that alter the consensus sequence at the intron 1 donor and acceptor splice sites, respectively. The other alleles harbor variants that alter the consensus sequence at transcription factor–binding sites in the intron 1 enhancer: specifically, , and at GATA-1 sites; and at a RUNX1 site; and at or near a C/EBP site. Molecular and serologic characterization of alleles can help in their future identification and in the resolution of discrepancies.