Fluorescent sensors are an essential part of the experimental toolbox of the life sciences, where they are used ubiquitously to visualize intra- and extracellular signaling. In the brain, optical neurotransmitter sensors can shed light on temporal and spatial aspects of signal transmission by directly observing, for instance, neurotransmitter release and spread. Here we report the development and application of the first optical sensor for the amino acid glycine, which is both an inhibitory neurotransmitter and a co-agonist of the N-methyl-d-aspartate receptors (NMDARs) involved in synaptic plasticity. Computational design of a glycine-specific binding protein allowed us to produce the optical glycine FRET sensor (GlyFS), which can be used with single and two-photon excitation fluorescence microscopy. We took advantage of this newly developed sensor to test predictions about the uneven spatial distribution of glycine in extracellular space and to demonstrate that extracellular glycine levels are controlled by plasticity-inducing stimuli.

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We thank Dr. O'Mara (Australian National University) for helpful discussions. Research was funded by the Human Frontiers Science Program Young Investigator Award (HFSP to H.J., C.H., and C.J.J.; grant number: RGY0084/2012), German Academic Exchange Service (DAAD-Go8) Travel Fellowship (to C.H. and C.J.J.), NRW-Rückkehrerprogramm (to C.H.), the European Union (ITN EU-GliaPhD) and German Research Foundation (DFG, SFB1089 B03, SPP1757 HE6949/1 and HE6949/3, to C.H.).

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Author notes

  1. These authors contributed equally: William H. Zhang, Michel K. Herde.


  1. Research School of Chemistry, Australian National University, Canberra, Australia

    • William H. Zhang
    • , Joshua A. Mitchell
    • , Jason H. Whitfield
    • , Vanessa Vongsouthi
    •  & Colin J. Jackson
  2. Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany

    • Michel K. Herde
    • , Andreas B. Wulff
    • , Daniel Minge
    • , Björn Breithausen
    •  & Christian Henneberger
  3. Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria

    • Inmaculada Sanchez-Romero
    •  & Harald Janovjak
  4. Institute of Neuropathology, University of Bonn Medical School, Bonn, Germany

    • Polina E. Gulakova
    •  & Susanne Schoch
  5. Australian Regenerative Medicine Institute (ARMI), Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Australia

    • Harald Janovjak
  6. European Molecular Biology Laboratory Australia (EMBL Australia), Monash University, Melbourne, Australia

    • Harald Janovjak
  7. German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany

    • Christian Henneberger
  8. UCL Institute of Neurology, London, UK

    • Christian Henneberger


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W.H.Z., J.A.M., V.V., J.H.W. and C.J.J. designed, produced and analyzed the sensor. M.K.H., J.H.W., A.B.W., W.H.Z., D.M., B.B. and C.H. performed and analyzed all experiments using two-photon excitation and electrophysiology in acute brain slices. M.K.H., J.H.W., I.S.-R., P.E.G., H.J., S.S. and A.B.W. performed studies on GlyFS expressed by cells. C.H., C.J.J. and H.J. designed the study. C.H., C.J.J. and W.H.Z. wrote the initial manuscript, to which all authors subsequently contributed.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Colin J. Jackson or Christian Henneberger.

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