Cell
Volume 177, Issue 5, 16 May 2019, Pages 1346-1360.e24
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Rational Engineering of XCaMPs, a Multicolor GECI Suite for In Vivo Imaging of Complex Brain Circuit Dynamics

https://doi.org/10.1016/j.cell.2019.04.007Get rights and content
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Highlights

  • Developing XCaMPs, a spectrally resolved, quadricolor (BGYR) suite of linear GECIs

  • Resolving PV interneuron spike trains and non-invasive imaging of hippocampal CA1

  • Cell-type-specific excitation-inhibition dynamics revealed by 3-color fiber photometry

  • Local dendritic inhibition identified in vivo via paired axon and dendrite recording

Summary

To decipher dynamic brain information processing, current genetically encoded calcium indicators (GECIs) are limited in single action potential (AP) detection speed, combinatorial spectral compatibility, and two-photon imaging depth. To address this, here, we rationally engineered a next-generation quadricolor GECI suite, XCaMPs. Single AP detection was achieved within 3–10 ms of spike onset, enabling measurements of fast-spike trains in parvalbumin (PV)-positive interneurons in the barrel cortex in vivo and recording three distinct (two inhibitory and one excitatory) ensembles during pre-motion activity in freely moving mice. In vivo paired recording of pre- and postsynaptic firing revealed spatiotemporal constraints of dendritic inhibition in layer 1 in vivo, between axons of somatostatin (SST)-positive interneurons and apical tufts dendrites of excitatory pyramidal neurons. Finally, non-invasive, subcortical imaging using red XCaMP-R uncovered somatosensation-evoked persistent activity in hippocampal CA1 neurons. Thus, the XCaMPs offer a critical enhancement of solution space in studies of complex neuronal circuit dynamics.

Keywords

genetically encoded calcium indicators
two-photon Ca2+ imaging
XCaMP
PV recording
paired pre- and post-synapse recording
non-invasive hippocampal recording
ckkap sequence
multiplex imaging

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14

These authors contributed equally

15

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