Direct Visualization of Live Zebrafish Glycan via Single-step Metabolic Labeling with Fluorophore-tagged Nucleotide Sugars

Dynamic turnover of cell-surface glycans is involved in a myriad of biological events, making this process an attractive target for in vivo molecular imaging. The metabolic glycan labeling coupled with bioorthogonal chemistry has paved the way for visulizing glycans in living organisms. However, a two-step labeling sequence is required, which is prone to tissue penetration difficulties of the imaging probes. Here, by exploring the substrate promiscuity of endogenous glycosyltransferases, we developed a single-step fluorescent glycan labeling strategy by using fluorophore-tagged analogs of nucleotide sugars directly. Injecting the fluorophore-tagged sialic acid and fucose into the yolk of zebrafish embryos at the one-cell stage enables a systematic imaging of sialylation and fucosylation in live zebrafish embryos at various developmental stages. From these studies, we obtained insights into the role of sialylated and fucosylated glycans in zebrafish hematopoiesis.