Bright and fast voltage reporters across the visible spectrum via electrochromic FRET (eFRET)

TL;DR

This paper introduces a new set of brightly fluorescent, fast, and spectrally diverse genetically encoded voltage indicators (GEVIs) that enable high-contrast, multicolor voltage imaging in neurons with rapid response times.

Contribution

It presents a novel electrochromic FRET (eFRET) mechanism for voltage sensing, expanding the spectral range and improving the speed and brightness of GEVIs.

Findings

Reported neuronal action potentials with high signal-to-noise ratio in cultured neurons.

Achieved response times as fast as 1 ms, suitable for real-time neural activity monitoring.

Enabled multicolor voltage imaging and combination with other optical tools.

Abstract

We present a palette of brightly fluorescent genetically encoded voltage indicators (GEVIs) with excitation and emission peaks spanning the visible spectrum, sensitivities from 6 - 10% Delta F/F per 100 mV, and half-maximal response times from 1 - 7 ms. A fluorescent protein is fused to an Archaerhodopsin-derived voltage sensor. Voltage-induced shifts in the absorption spectrum of the rhodopsin lead to voltage-dependent nonradiative quenching of the appended fluorescent protein. Through a library screen, we identified linkers and fluorescent protein combinations which reported neuronal action potentials in cultured rat hippocampal neurons with a single-trial signal-to-noise ratio from 6.6 to 11.6 in a 1 kHz imaging bandwidth at modest illumination intensity. The freedom to choose a voltage indicator from an array of colors facilitates multicolor voltage imaging, as well as combination with other optical reporters and optogenetic actuators.