Glycobiology Advance Access originally published online on January 9, 2008
Glycobiology 2008 18(3):242-249; doi:10.1093/glycob/cwm138
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Embryonic stem cells deficient in I β1,6-N-acetylglucosaminyltransferase exhibit reduced expression of embryoglycan and the loss of a Lewis X antigen, 4C9
2 Department of Biochemistry
3 Division of Disease Models, Center for Neurological Disease and Cancer, Nagoya University Graduate School of Medicine, Nagoya 468-8550
4 Section of Gene Expression Regulation, Frontier Science Research Center, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065
5 Department of Health Science, Faculty of Psychological and Physical Sciences, Aichi Gakuin University, 12 Araike, Nisshin, Aichi 470-0195, Japan
1 To whom correspondence should be addressed: Tel: +81-561-73-1111; Fax: +81-561-73-1142; e-mail: tmurama{at}dpc.aichi-gakuin.ac.jp
Received on November 15, 2007; revised on December 21, 2007; accepted on December 21, 2007
Embryoglycan is a class of branched high-molecular-weight poly-N-acetyllactosamines characteristically expressed in early embryonic cells and has been shown to be involved in the intercellular adhesion of early embryonic cells in vitro. Branching of poly-N-acetyllactosamine chains is performed by β1,6-N-acetylglucosaminylation of the galactosyl residue. We previously knocked out the gene encoding I β1, 6-N-acetylglucosaminyltransferase (IGnT), and the resultant deficient mice were born without any abnormality, although the mice exhibited various deficits in later life. In the present investigation, we produced embryonic stem (ES) cells from IGnT-deficient embryos. The mutant ES cells exhibited a reduced capability in embryoglycan synthesis. Thus, IGnT is a major enzyme involved in the branching of poly-N-acetyllactosamine chains in embryoglycan. Since ES cells are equivalent to multipotential cells of the embryonic ectoderm in early postimplantation embryos, this result indicates that an abundance of embryoglycan in these cells is not essential for normal embryogenesis. The IGnT-deficient ES cells continued to express SSEA-1, but lacked the expression of 4C9 antigen, although the epitope of 4C9 antigen was confirmed to be Lewis X by a transfection experiment. The result establishes the distinct nature of 4C9 antigenicity, which requires either Lewis X epitope on I-branch or clustering of Lewis X epitope, best accomplished by poly-N-acetyllactosamine branching. 
6-Integrin was newly identified as a carrier of embryoglycan. The IGnT-deficient ES cells adhered to dishes coated with laminin, which is a ligand for 6-integrin, significantly less than wild-type ES cells, raising the possibility that embryoglycan in ES cells enhances 6-integrin-dependent adhesion in vitro.
Key words: Embryonic stem cells / knockout mice / Lewis X / N-acetylglucosaminyltransferase / poly-N-acetyllactosamines