Deletion of the RUNX1 binding site in the erythroid cell‐specific regulatory element of the ABO gene in two individuals with the Am phenotype

• DOI: 10.1111/vox.12077
• Publication Date: 2013-09-02T05:06:45Z
• Authors: Y. Takahashi; K. Isa; R. Sano; T. Nakajima; R. Kubo; K. Takahashi; Y. Kominato; H. Tsuneyama; K. Ogasawara; M. Uchikawa
• Keywords: Binding Sites; Base Sequence; Transcription, Genetic; Molecular Sequence Data; Introns; ABO Blood-Group System; 03 medical and health sciences; Enhancer Elements, Genetic; Phenotype; 0302 clinical medicine; Core Binding Factor Alpha 2 Subunit; Humans; Regulatory Elements, Transcriptional; K562 Cells; Promoter Regions, Genetic; Alleles; Sequence Deletion

Background and ObjectivesAn erythroid cell‐specific regulatory element, referred to as the +5·8‐kb site, had been identified in the first intron of the human ABO blood group gene. Subsequent studies revealed that either a 5·8‐kb deletion including the +5·8‐kb site or disruption of a GATA factor binding motif at the site was present in all Bm and ABm individuals examined. We investigated the molecular mechanism of the Am phenotype, which is analogous to the Bm phenotype.Materials and MethodsGenomic DNAs were prepared from peripheral blood of two Am individuals, and the nucleotide sequences were investigated using PCR and direct sequencing. Electrophoretic mobility shift assay (EMSA) and promoter assay with K562 cells were carried out.ResultsA novel 23‐bp nucleotide deletion was found at the +5·8‐kb site in both individuals. EMSAs demonstrated binding of the transcription factor RUNX1 to the nucleotides within the deletion. Promoter assays showed that the deletion reduced the transcriptional activity of the +5·8‐kb site.ConclusionDeletion of the 23‐bp nucleotides including the RUNX1 binding site decreases transcription of the A allele, resulting in the reduction in A antigen expression in the Am phenotype.