BiPOLES: a tool for bidirectional dual-color optogenetic control of neurons

Optogenetic manipulation of neuronal activity has become an indispensable experimental strategy in neuroscience research. A large repertoire of excitatory and inhibitory tools allows precise activation or inhibition of genetically targetable neuronal populations. However, an optogenetic tool for reliable bidirectional control of neuronal activity allowing both up- and downregulation of the same neurons in a single experiment is still missing. Here we report BiPOLES, an optogenetic tool for potent excitation and inhibition of the same population of neurons with light of two different colors. BiPOLES consists of an inhibitory, blue-light-sensitive anion-conducting channelrhodopsin fused to an excitatory, red-light-sensitive cation-conducting channelrhodopsin in a single, trafficking-optimized tandem protein. BiPOLES enables multiple new applications including potent dual-color spiking and silencing of the same neurons in vivo and dual-color optogenetic control of two independent neuronal populations.