Bimodal activation of different neuron classes with the spectrally red-shifted channelrhodopsin chimera C1V1 in Caenorhabditis elegans

PLoS One. 2012;7(10):e46827. doi: 10.1371/journal.pone.0046827. Epub 2012 Oct 3.

Abstract

The C. elegans nervous system is particularly well suited for optogenetic analyses of circuit function: Essentially all connections have been mapped, and light can be directed at the neuron of interest in the freely moving, transparent animals, while behavior is observed. Thus, different nodes of a neuronal network can be probed for their role in controlling a particular behavior, using different optogenetic tools for photo-activation or -inhibition, which respond to different colors of light. As neurons may act in concert or in opposing ways to affect a behavior, one would further like to excite these neurons concomitantly, yet independent of each other. In addition to the blue-light activated Channelrhodopsin-2 (ChR2), spectrally red-shifted ChR variants have been explored recently. Here, we establish the green-light activated ChR chimera C1V1 (from Chlamydomonas and Volvox ChR1's) for use in C. elegans. We surveyed a number of red-shifted ChRs, and found that C1V1-ET/ET (E122T; E162T) works most reliable in C. elegans, with 540-580 nm excitation, which leaves ChR2 silent. However, as C1V1-ET/ET is very light sensitive, it still becomes activated when ChR2 is stimulated, even at 400 nm. Thus, we generated a highly efficient blue ChR2, the H134R; T159C double mutant (ChR2-HR/TC). Both proteins can be used in the same animal, in different neurons, to independently control each cell type with light, enabling a further level of complexity in circuit analyses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / radiation effects
  • Animals
  • Behavior, Animal / physiology
  • Behavior, Animal / radiation effects
  • Caenorhabditis elegans / cytology
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans / physiology
  • Caenorhabditis elegans / radiation effects*
  • Color
  • GABAergic Neurons / cytology
  • GABAergic Neurons / radiation effects
  • Motor Neurons / cytology
  • Motor Neurons / radiation effects
  • Muscle Contraction / radiation effects
  • Muscles / cytology
  • Muscles / physiology
  • Muscles / radiation effects
  • Neurons / cytology*
  • Neurons / metabolism
  • Neurons / radiation effects*
  • Recombinant Fusion Proteins / metabolism*
  • Rhodopsin / metabolism*
  • Spectrum Analysis

Substances

  • Recombinant Fusion Proteins
  • Rhodopsin

Grants and funding

This work was funded by the Deutsche Forschungsgemeinschaft (DFG) by grants HE3824/9-3, 9-4, and FOR1279-P8 to PH and SFB807-P11 and FOR1279-P1 to AG. Website of the DFG: www.dfg.de/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.