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Using infrared fluorescent protein (iRFP) for monitoring and modulating neuronal activity

Wednesday, November 06, 2013 — Poster Session I

4:00 p.m. – 6:00 p.m.

FAES Academic Center (Upper-Level Terrace)




  • C.T. Richie
  • L.R. Whitaker
  • L.V. Fortuno
  • H.A. Baldwin
  • D.B. Howard
  • J.J. Hinkle
  • Y.J. Zhang
  • M.A. Verdecia
  • B.T. Hope
  • B.K. Harvey


The use of fluorescent reporter genes is essential for the identification and observation of cells that express transgenic modulatory proteins such as light-activated ion channels (aka optogenetics) or designer receptors activated by designer drugs (DREADD technology). Many of the vectors that express a neuromodulator coexpress a fluorescent protein such as yellow (YFP) or red fluorescent protein (RFP). Infrared fluorescent protein (iRFP) can improve the resolution of imaging in brain tissue because the excitation/emission spectra of iRFP has minimal overlap with hemoglobin and the emitted light from iRFP is less scattered by the tissue. We have generated a set of adeno-associated vectors (AAVs) in which iRFP is fused to channel rhodopsin (ChR2) and halorhodopsin (eNpHR3.0) and can be expressed either constitutively or conditionally (Cre-dependent). We demonstrate that iRFP fluorescence is detectable in neurons both in vitro and in vivo. iRFP exhibits minimal photobleaching compared to YFP. Electrophysiological recordings from iRFP-labeled cells compared to other FP-labeled cells suggest that iRFP cells are more stable. Overall, we show that iRFP can be used as a reporter with minimal impact on viability and function thereby making it feasible to extend the resolution limits for imaging and manipulating genetically-tagged neurons in slices and in vivo.

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