Bio-orthogonal Glycan Imaging of Culture Cells and Whole AnimalC. eleganswith Expansion Microscopy

Abstract

AbstractComplex carbohydrates called glycans play crucial roles in the regulation of cell and tissue physiology, but how glycans map to nanoscale anatomical features must still be resolved. Here, we present the first nanoscale map of mucin-typeO-glycans throughout the entirety of theCaenorhabditis elegansmodel organism. We construct a library of multifunctional linkers to probe and anchor metabolically labelled glycans in expansion microscopy (ExM), an imaging modality that overcomes the diffraction limit of conventional optical microscopes through the physical expansion of samples embedded in a polyelectrolyte gel matrix. A flexible strategy is demonstrated for the chemical synthesis of linkers with a broad inventory of bio-orthogonal functional groups, fluorophores, anchorage chemistries, and linker arms. EmployingC. elegansas a test bed, we resolve metabolically labelledO-glycans on the gut microvilli and other nanoscale anatomical features using our ExM reagents and optimized protocols. We use transmission electron microscopy images ofC. elegansnano-anatomy as ground truth data to validate the fidelity and isotropy of gel expansion. We construct whole organism maps ofC. elegans O-glycosylation in the first larval stage and identifyO-glycan “hotspots” in unexpected anatomical locations, including the body wall furrows. BeyondC. elegans, we provide validated ExM protocols for nanoscale imaging of metabolically labelled glycans on cultured mammalian cells. Together, our results suggest the broad applicability of the multifunctional reagents for imaging glycans and other metabolically labelled biomolecules at enhanced resolutions with ExM.Graphical abstract