Review of ABO Expression and Variations based on Transcriptional Regulation of the ABO Blood Group Gene

Background and Summary: We review the transcriptional regulation of ABO expression and discuss variants in the promoter and erythroid cell-specific regulatory region in individuals with weak ABO phenotypes such as B-m, A(m), B-3, and A(3). We also review the molecular mechanisms responsible for variations in ABO expression in development and disease including the cell type-specific expression of ABO during erythroid cell differentiation, and reduction of A- or B-antigens in cancer cells or on red blood cells in patients with leukemia. Although the relationship between ABO blood group antigens and diseases has been characterized, the physiological significance of the ABO blood group system remains unclear. Key Messages: This review discusses accumulated knowledge of the ABO gene regulation and potential reasons for conservation of ABO during evolution.