Investigating the feasibility of channelrhodopsin variants for nanoscale optogenetics

Markus A. Stahlberg; Charu Ramakrishnan; Katrin I. Willig; Edward S. Boyden; Karl Deisseroth; Camin Dean

doi:10.1117/1.NPh.6.1.015007

28 February 2019 Investigating the feasibility of channelrhodopsin variants for nanoscale optogenetics

Markus A. Stahlberg, Charu Ramakrishnan, Katrin I. Willig, Edward S. Boyden, Karl Deisseroth, Camin Dean

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Neurophotonics, Vol. 6, Issue 1, 015007 (February 2019). https://doi.org/10.1117/1.NPh.6.1.015007

Abstract

Optogenetics has revolutionized the study of circuit function in the brain, by allowing activation of specific ensembles of neurons by light. However, this technique has not yet been exploited extensively at the subcellular level. Here, we test the feasibility of a focal stimulation approach using stimulated emission depletion/reversible saturable optical fluorescence transitions-like illumination, whereby switchable light-gated channels are focally activated by a laser beam of one wavelength and deactivated by an overlapping donut-shaped beam of a different wavelength, confining activation to a center focal region. This method requires that activated channelrhodopsins are inactivated by overlapping illumination of a distinct wavelength and that photocurrents are large enough to be detected at the nanoscale. In tests of current optogenetic tools, we found that ChR2 C128A/H134R/T159C and CoChR C108S and C108S/D136A—activated with 405-nm light and inactivated by coillumination with 594-nm light—and C1V1 E122T/C167S—activated by 561-nm light and inactivated by 405-nm light—were most promising in terms of highest photocurrents and efficient inactivation with coillumination. Although further engineering of step-function channelrhodopsin variants with higher photoconductances will be required to employ this approach at the nanoscale, our findings provide a framework to guide future development of this technique.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Markus A. Stahlberg, Charu Ramakrishnan, Katrin I. Willig, Edward S. Boyden, Karl Deisseroth, and Camin Dean "Investigating the feasibility of channelrhodopsin variants for nanoscale optogenetics," Neurophotonics 6(1), 015007 (28 February 2019). https://doi.org/10.1117/1.NPh.6.1.015007

Received: 17 October 2018; Accepted: 5 February 2019; Published: 28 February 2019

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