In comprehensive glycome analysis with a high-density lectin microarray, we have previously shown that the recombinant N-terminal domain of the lectin BC2L-C from Burkholderia cenocepacia (rBC2LCN) binds exclusively to undifferentiated human induced pluripotent stem (iPS) cells and embryonic stem (ES) cells but not to differentiated somatic cells. Here we demonstrate that podocalyxin, a heavily glycosylated type1 transmembrane protein, is the predominant glycoprotein ligand of rBC2LCN on human iPS cells and ES cells. When analyzed by DNA microarray, podocalyxin was found to be highly expressed in both iPS cells and ES cells. Western and lectin blotting revealed that rBC2LCN binds predominantly to podocalyxin with a high molecular weight of more than 240 kDa in undifferentiated iPS cells of six different origins and four ES cell lines, but no binding was observed in either differentiated mouse feeder cells or somatic cells. The specific binding of rBC2LCN to podocalyxin prepared from a large set of iPS cells (138 types) and ES cells (15 types) was also confirmed using a high-throughput antibody-overlay lectin microarray. Alkaline digestion greatly reduced the binding of rBC2LCN to podocalyxin, indicating that the major glycan ligands of rBC2LCN are presented on O-glycans. Furthermore, rBC2LCN was found to exhibit significant affinity to a branched Oglycan comprising an H type3 structure as the most probable rBC2LCN glycan ligand (Kd, 4.0 x 10-5 M) prepared from human 201B7 iPS cells, suggesting that H type3 is a novel potential pluripotency marker. We conclude that podocalyxin is the predominant glycoprotein ligand of rBC2LCN on human iPS cells and ES cells.
Overall design
Gene expressions in human embryonic stem cells (ESCs) and human induced pluripotent stem cells (iPSCs). Human iPS cells (MRC5-iPS, AM-iPS, UtE-iPS, PAE-iPS) were induced from four different somatic cells by infection of the retroviral vectors pMXs encoding OCT3/4, SOX2, KLF4 and c-MYC, simultaneously. Human iPS cells (TIG/MKOS#19, #56, #106) were generated through reprogramming by Sendai virus infection-mediated expression of OCT4, SOX2, KLF4, and c-MYC.
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