Christian G. Bochet

Efficient tools for controlling molecular functions with exquisite spatiotemporal resolution are much in demand to investigate biological processes in living systems. Here we report an easily synthesized caged dexamethasone for photo‐activating cytoplasmic proteins fused to the glucocorticoid receptor. In the dark, it is stable in vitro as well as in vivo in both zebrafish ( Danio rerio ) and Xenopus sp , two significant models of vertebrates. In contrast, it liberates dexamethasone upon UV illumination, which has been harnessed to interfere with developmental steps in embryos of these animals. Interestingly, this new system is biologically orthogonal to the one for photo‐activating proteins fused to the estrogen ERT receptor, which brings great prospect for activating two distinct proteins down to the single cell level.