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TitleA Bright and Fast Red Fluorescent Protein Voltage Indicator That Reports Neuronal Activity in Organotypic Brain Slices.
Publication TypeJournal Article
Year of Publication2016
AuthorsAbdelfattah, Ahmed S., Samouil L. Farhi, Yongxin Zhao, Daan Brinks, Peng Zou, Araya Ruangkittisakul, Jelena Platisa, Vincent A. Pieribone, Klaus Ballanyi, Adam E. Cohen, and Robert E. Campbell
JournalJ Neurosci
Date Published2016 Feb 24

UNLABELLED: Optical imaging of voltage indicators based on green fluorescent proteins (FPs) or archaerhodopsin has emerged as a powerful approach for detecting the activity of many individual neurons with high spatial and temporal resolution. Relative to green FP-based voltage indicators, a bright red-shifted FP-based voltage indicator has the intrinsic advantages of lower phototoxicity, lower autofluorescent background, and compatibility with blue-light-excitable channelrhodopsins. Here, we report a bright red fluorescent voltage indicator (fluorescent indicator for voltage imaging red; FlicR1) with properties that are comparable to the best available green indicators. To develop FlicR1, we used directed protein evolution and rational engineering to screen libraries of thousands of variants. FlicR1 faithfully reports single action potentials (∼3% ΔF/F) and tracks electrically driven voltage oscillations at 100 Hz in dissociated Sprague Dawley rat hippocampal neurons in single trial recordings. Furthermore, FlicR1 can be easily imaged with wide-field fluorescence microscopy. We demonstrate that FlicR1 can be used in conjunction with a blue-shifted channelrhodopsin for all-optical electrophysiology, although blue light photoactivation of the FlicR1 chromophore presents a challenge for applications that require spatially overlapping yellow and blue excitation.

SIGNIFICANCE STATEMENT: Fluorescent-protein-based voltage indicators enable imaging of the electrical activity of many genetically targeted neurons with high spatial and temporal resolution. Here, we describe the engineering of a bright red fluorescent protein-based voltage indicator designated as FlicR1 (fluorescent indicator for voltage imaging red). FlicR1 has sufficient speed and sensitivity to report single action potentials and voltage fluctuations at frequencies up to 100 Hz in single-trial recordings with wide-field microscopy. Because it is excitable with yellow light, FlicR1 can be used in conjunction with blue-light-activated optogenetic actuators. However, spatially distinct patterns of optogenetic activation and voltage imaging are required to avoid fluorescence artifacts due to photoactivation of the FlicR1 chromophore.

Alternate JournalJ. Neurosci.
PubMed ID26911693
PubMed Central IDPMC4764664
Grant ListR01 NS083875 / NS / NINDS NIH HHS / United States
U01 NS090565 / NS / NINDS NIH HHS / United States