The detailed frequencies distribution of ABO alleles was studied in the Chinese Han population. We identified 14 alleles, including 3 novel alleles.

There are significant differences in the frequencies and molecular characteristics of D variants among indigenous Chinese populations, compared to Caucasian and African populations, which must be considered when developing clinical practices related to D variant blood donors, transfusion recipients, or obstetrical patients.

<b><i>Introduction:</i></b> The characteristic of ABO blood subgroup is crucial for elucidating the mechanisms of such variant phenotypes and offering useful information in blood transfusion. <b><i>Methods:</i></b> In total, 211 ABO variants including part of available family members were investigated in this study. The phenotypes of these individuals were typed with serologic methods. The full coding regions of <i>ABO</i> gene and the erythroid cell-specific regulatory elements in intron 1 of them were amplified with polymerase chain reaction and then directly sequenced. The novel alleles were confirmed by cloning and sequencing. Phylogenetic tree was made using CLUSTAL W software. 3D structural analyses of the glycosyltransferases (GTs) with some typical mutations were performed by PyMOL software. <b><i>Results:</i></b> Forty-eight distinctly rare <i>ABO</i> alleles were identified in 211 Chinese variant individuals, including 16 novel <i>ABO</i> alleles. All of the alleles were categorized as 5 groups: 16 <i>ABO</i>*<i>A</i> alleles, 23<i> ABO</i>*<i>B</i> alleles, 4 <i>ABO</i>*<i>BA</i> alleles, 4 <i>ABO</i>*<i>cisAB</i> alleles, and 1 <i>ABO</i>*<i>O</i> alleles. <i>ABO</i>*<i>A2.08</i> and <i>ABO</i>*<i>BA.02</i> were the relatively predominant <i>A</i> and <i>B</i> subgroup alleles, respectively. According to the phylogenetic tree, 28 alleles (5 common alleles and 23 alleles identified in our laboratory) were classified into 3 major allelic lineages. The structural analysis of 3D homology modeling predicted reduced protein stability of the mutant GTs and may explain the reduced ABO antigen expression. <b><i>Conclusions:</i></b> The molecular basis of ABO variants was analyzed, and 16 novel <i>ABO</i> alleles were identified. The results extended the information of ABO variants and provided a basis for better transfusion strategies and helped to improve blood transfusion safety.

The PCR-SBT method is reliable and accurate for HPA genotyping, suitable for routine HPA analysis, and can screen large numbers of donors. We identified 14 new polymorphisms, two of which led to amino acid changes.

The study suggested that the transcriptional activity of the +5·8 kb site could be downregulated by the single point mutation of RUNX1 motif, leading to reduction in A or B antigen expression.