Imaging dynamic cell-cell junctional coupling in vivo using Trojan-LAMP

To study the physiological regulation and function of cell-cell gap junction communication in vivo, we developed a bioconjugate of caged dye, named dextran-CANPE-HCC, for imaging cell coupling in small model organisms. In vitro, the compound was photolyzed efficiently with robust fluorescence enhancement. Dextran-CANPE-HCC delivered into Caenorhabditis elegans oocytes was retained in cells throughout development. Using local uncaging, we photolyzed dextran-CANPE-HCC to release the small HCC dye and imaged the dynamics of intercellular dye transfer through gap junction channels, a technique we named Trojan-local activation of molecular fluorescent probes (LAMP). Early during embryonic development, the pattern of cell coupling undergoes dramatic remodeling and imaging revealed that the germ cell precursors, P2, P3 and P4, were isolated from the somatic cell communication compartment. As dextran-CANPE-HCC is chemically and metabolically stable, labeled worms showed very bright signal upon photoactivation after hatching, which allowed us to examine cell coupling in living worms noninvasively.