Supplementary Material for: Molecular Basis of ABO Variants Including Identification of 16 Novel <b><i>ABO</i></b> Subgroup Alleles in Chinese Han Population Y.Ying X.Hong X.Xu S.Chen J.He F.Zhu X.Xie 2019 <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.