Human embryonic stem cell N-glycan features relevant to pluripotency

Abstract

Human embryonic stem cells (hESCs) and reprogrammed human induced pluripotent stem cells (hiPSCs) proliferate indefinitely in the undifferentiated state (self-renewal) and differentiate into the three germ layers (and ultimately into all cell types) (pluripotency). Branching in the N-glycan core of hESCs/hiPSCs is limited. hESCs/hiPSCs have high mannose-type and biantennary complex-type core structures, indicating immature stages of N-glycoproteins. The two branches on the core consist of type 2 N-acetyllactosamine (LacNAc), completed mainly with α 2,6-linked sialic acid. Complex terminal fucosylation, particularly α 1,2-linked fucosylation, is another characteristic N-glycosylation feature of hESCs/hiPSCs. All of these structural features are probably associated with the pluripotency of hESCs/hiPSCs. In differentiated cells, two-, three-, and four-branched N-glycan core structures are seen and N-acetylhexosamine compositions increase in the branches. The elongation and size of the branches in the N-glycan cores increase by the addition of poly-LacNAc chains and are the typical features during differentiation. As α 1,2-linked terminal fucosylation disappears, α 1,6-linked core fucosylation increases. It is necessary to know the pluripotency-associated glycans in order to identify and isolate the pluripotent cells from heterogeneous populations containing differentiated cells.