Photoactivatable genetically encoded calcium indicators for targeted neuronal imaging

The photoactivatable calcium sensors reported in this paper allow simultaneous highlighting of cellular morphology and recording of calcium activity, which is demonstrated in neuronal cultures, in Drosophila and in zebrafish. Circuit mapping requires knowledge of both structural and functional connectivity between cells. Although optical tools have been made to assess either the morphology and projections of neurons or their activity and functional connections, few probes integrate this information. We have generated a family of photoactivatable genetically encoded Ca 2+ indicators that combines attributes of high-contrast photolabeling with high-sensitivity Ca 2+ detection in a single-color protein sensor. We demonstrated in cultured neurons and in fruit fly and zebrafish larvae how single cells could be selected out of dense populations for visualization of morphology and high signal-to-noise measurements of activity, synaptic transmission and connectivity. Our design strategy is transferrable to other sensors based on circularly permutated GFP (cpGFP).