Imaging Membrane Lipid Order in Whole, Living Vertebrate Organisms

We report the first imaging of membrane lipid order in a whole, living vertebrate organism. This was achieved with the phase-sensitive, membrane-partitioning probe Laurdan in conjunction with multiphoton microscopy to image cell membranes in various tissues of live zebrafish embryos in three dimensions, including hindbrain, retina, muscle, gut, and kidney. The data also allowed quantitative analysis of membrane order, which showed high lipid order in the apical surfaces of polarized epithelial cells. The transition of membrane order imaging from cultured cell lines to living organisms is an important step forward in understanding the physiological relevance of membrane microdomains including lipid rafts.