Optimization of genetically encoded GABA indicator

The GENIE Project Team at HHMI Janelia has developed a second-generation genetically encoded GABA indicator, in collaboration with Jonathan Marvin and Loren Looger. The sensor is based on iGABASnFR (1), and has the following features, tested extensively in cultured neurons: Positive-going version (iGABASnFR2) and negative-going version (iGABASnFR2n) iGABASnFR2: 4x higher sensitivity to APs than iGABASnFR, iGABASnFR2n: 2x higher sensitivity to APs than iGABASnFR. Both enable single-AP high-speed imaging Enables detection of signal in individual dendrites and synaptic boutons Higher affinity for GABA (iGABASnFR2: EC50: 6.4±0.2 μM, ~7x tighter than iGABASnFR, ΔF/Fmax=0.5±0.05, ~2x higher than iGABASnFR) Imaged with standard GFP filter set