Live imaging of endogenous protein dynamics in zebrafish using chromobodies

Chromobodies are intracellular nanoprobes that combine the specificity of antibodies with the convenience of live fluorescence imaging in a flexible, DNA-encoded reagent. Here, we present the first application of this technique to an intact living vertebrate organism. We generated zebrafish lines expressing chromobodies that trace the major cytoskeletal component actin and the cell cycle marker PCNA with spatial and temporal specificity. Using these chromobodies, we captured full localization dynamics of the endogenous antigens in different cell types and at different stages of development. For the first time, the chromobody technology enables live imaging of endogenous subcellular structures in an animal, with the remarkable advantage of avoiding target protein overexpression or tagging. In combination with improved chromobody selection systems, we anticipate a rapid adaptation of this technique to new intracellular antigens and model organisms, allowing the faithful description of cellular and molecular processes in their dynamic state.